Update: since publishing this article commenters have made us aware of 3 other hot water diverters on the Australian market, the ‘Dimplex Free-E’ and, The Fronius OhmPilot and a unit from SolarEdge. We’ll add these to the comparison table as soon as we have enough info. If you know of any others let us know.
I recently wrote about solar hot water diverters. These devices use your surplus solar electricity to power your hot water cylinder.
They can cut your electricity bills provided your solar feed-in tariff is less than the cost of the grid electricity used to heat your water — which is not always the case.
I am going to assume you’ve read my earlier article, done your research, and decided a solar hot water diverter is for you. You’ve either determined it will save you money or it was love at first comprehension of the concept and you’ve realized you can’t live without one. So the question becomes, which diverter should you choose?
To help you with your decision, here at SolarQuotes, we1 have tried to track down every diverter on sale in Australia. For the ones we’ve found, we’ve researched their retail price and specifications and put the results into our Solar Hot Water Diverter Comparison Table.
See details of solar hot water diverters available in Australia in our new diverter comparison table.
The iBoost Is Not Available In Australia
The iBoost is a diverter from the UK that was marketed in Australia, but has since disappeared and we have been unable to contact the company. As there is no evidence they have a presence in Australia, they are not included on the table.
About Controlled Load and Economy Tariffs
Devices on controlled load or economy tariffs must be hardwired2. They cannot be connected to any other power source except the controlled load/economy tariff meter. So a hot water element connected to solar via a diverter cannot also be connected to a controlled load or economy tariff3.
A workaround is to use a dual element hot water system. Connect the upper element to a diverter and the lower element to the controlled load/economy tariff. The latter is set to a lower temperature than the diverter element. This reduces the amount of grid electricity used to heat the water. But the lower temperature set point should be at least 60 degrees to control the growth of Legionella and other dangerous microorganisms. 20-30% of hot water systems have 2 elements and they are more common in colder areas.
Comparing Diverter Features
The diverter information came from the companies that supply them, or in the case of the Powerdiverter, it was scraped off the internet. I will go through the details of the four different diverters on the comparison table and see if I can arrive at any firm conclusions about which diverter will rise triumphant from the solar electric hot water Thunderdome:
Price: The number of dollarydoos they cost. Catch Power gives the installed cost of their diverters while the others just give the hardware cost, so you’ll need a separate quote for installation.
If a company claims their diverter only takes minutes to install, don’t get optimistic about the installation cost. Technically, my beard only took minutes to grow. While diverters do not need an accredited solar installer, they do need a qualified electrician and so you will probably need to pay at least $200 for installation. I expect the real cost to be from $250 to $350.
Single Phase or 3 Phase: Most homes have single phase power, but an increasing number have 3 phase. If your home has a large ducted air conditioner4 that serves multiple rooms there is a good chance you have 3 phase power. Three phase diverters are more complex and so cost more. They also take more effort to connect, increasing the installation cost.
Maximum Heating Element Capacity: The electrical power diverters send to hot water systems is variable and depends on the amount of surplus solar electricity supplied. This variable output can only be used for heating elements. If used with anything that has pumps, motors, or electronics there is a very high risk the magic smoke inside that makes them work will escape5.
The biggest element in a normal household hot water systems is 4.8 kilowatts. Only two of the four diverters can cope with an element that large, but they can all handle a 3.6 kilowatt element, which is the next step down.
Number of Heating Load Outputs: Most people will only want to use their diverter for a single hot water system and nothing else. But if you want to run a second hot water system using the same diverter, or potentially another device with a heating element, such as a bar heater or floor heating, then you’ll want a diverter with two variable heating load outputs.
Sensor Connection: All diverters have a Current Transformer (CT) sensor that goes just after the electricity meter to measure when surplus solar is being exported. This sensor is normally connected by a wire to the diverter, but some can use a wireless link. Handy if your meter box is a long way from your hot water cylinder.
Timer: If a diverter has a timer it can use off-peak electricity rates to heat water. This feature won’t save most solar households money, as they are usually better off on a standard tariff, but some solar households may benefit from a time-of-use tariff, especially those with battery storage.
Grid Power Boost: If a diverter doesn’t receive enough surplus solar electricity to heat water it will boost its temperature using grid electricity. While all diverters can all be manually boosted with the twist of a knob, they can also ‘intelligently’ choose when to boost.
Special Features: One diverter offers internet monitoring and takes advantage of weather forecasts to optimise time-of-use tariffs.
Another diverter offers ‘threshold power’ to appliances that don’t mind their power being cut and reconnected multiple times per day (such as a pool pump or hydroponics heater). This feature allows you to configure the diverter with the power draw of the appliance, and only power it when there is both surplus solar, and your hot water is at temperature.
Warranty: The length of the written warranty.
Hype: An example of a ridiculous or over the top statement a company has made about their diverter.
Catch Power: Green Catch And Blue Catch
Can you guess which Catch Power this is? (Hint: It’s not Catch Power Blue.)
I am going to proceed in alphabetical order.
Catch Power makes 2 diverters, Green and Blue, which are both manufactured in Australia. The Green Catch is single phase. The fancier Blue Catch has a single phase version and a 3 phase version should come out this month. The characteristics they have in common are:
Maximum Heating Element Capacity: 4.8 kilowatts6.
Number of Heating Load Outputs: 1
Timer: Yes.
Warranty: 5 years.
The Catch Power Green
Price: The installed cost of the Catch Power Green is given as $1,000.
Phases: Single phase.
Sensor Connection: Wired.
Grid Power Boost: The Catch Power Green will boost the hot water system’s temperature for a set period each night. The time period can be reduced in summer and increased in winter. It can also adjust the period automatically.
If the hot water system doesn’t reach its maximum temperature for two days will heat the water at night using grid power until it reaches the system’s maximum temperature, which will be at least 60 degrees. (A common setting is 65 degrees. Higher than this greatly increases the risk of serious scalding injuries if the system doesn’t have a tempering valve.) This will prevent dangerous microorganisms such as Legionella from getting a foothold in the tank.
It can also be manually boosted by twisting a knob.
Special Features: Nope. It’s just a diverter. And that’s fine.
UPDATE: January 3, 2019 – the new Catch Power Green is now available. It’s smaller, cuter and cheaper – check out my review.
The Catch Power Blue
Price: The installed cost of the Blue Catch is given as $1,700 for the single phase version and $1,950 for the 3 phase version.
Phases: Single phase or 3 phase.
Sensor Connection: Wired connection from the meter sensor to the diverter with a wireless connection to its communicator which plugs in to your modem or router.
Grid Power Boost: The Blue Catch is internet connected and monitors the household’s energy consumption and hot water use. It receives a weather report at 11pm every night and uses that along with the information it has gathered to intelligently decide how much grid electricity it will need to use to boost the hot water temperature. It will do this at night so households on time-of-use tariffs can make use of off-peak rates.
Catch Power says they do not know how much much more efficient this is than the Green Catch, as they have not had enough time to make a reasonable comparison.
Special Features: The internet connection allows remote monitoring by Catch Power to detect any problems.
Both the weather forecasting and monitoring are dependent on Catch Power’s servers staying in operation. The possibility of servers going offline is important to keep in mind when purchasing anything that makes use of the cloud and isn’t a monkey god.
Catch Power’s Warranty Is Catch-22
The Catch Power Green and Blue both come with 5 year warranties. I will juxtaposition two sentences from their warranty documents to highlight a problem:
Under Australian Consumer Law you are entitled to claim compensation for consequential losses from a product not working as it should if the losses are reasonably foreseeable.
I’m no lawyer, but I would say having to pay an electrician to remove a faulty unit and replace it with a new one is a loss resulting from the failure of the original unit. The resulting cost is very foreseeable by anyone who is even only slightly reasonable. This makes me believe a consumer would be entitled to compensation for those losses[1. Manufacturers and installers not understanding their obligations under Australian Consumer Law is a problem in the solar (and many other) industries. I will cover this in a future post.].
Catch Power’s Hype
I am going to confine myself to addressing one piece of hype for each diverter and for Catch Power I will stick to one simple statement that strikes me as misleading:
Apart from a few exceptions7, no one on-grid can use a diverter to create free hot water. If a household uses one kilowatt-hour of solar electricity to heat water that kWh is not sent into the grid for a feed-in tariff. The cost of that kWh is equal to the forgone feed-in tariff. It’s not free.
There are plenty of people in Australia receiving a feed-in tariff higher than their controlled load tariff, these people would lose money.
Claiming a diverter will let you create free hot water from your excess solar power is like your boss claiming she provides free soft drinks at work when she actually deducts $1 from your pay for each can you drink. You may be happy to pay only $1 a can and think it’s a good deal, but it’s not the same as free.
The Paladin-2
The Paladin-2 is a solar hot water diverter designed and manufactured in New Zealand. This version is modified for Australian conditions and temperatures. Unless you live in Tasmania, make sure you have the Australian version.
Price: $790 uninstalled.
Phases: Single phase.
Maximum Heating Element Capacity: 4 kilowatts. In practice this means the largest standard sized heating element it can use is 3.6 kilowatts.
Number of Heating Load Outputs: 1
Update 12th of October 2020: It has kindly been pointed out to me that at the time this article was written the Paladin 2 in Australia should have had 2 heating load outputs. (I was going to provide a link to the datasheet of their latest model, but couldn’t find one on their site.)
Sensor Connection: Wired sensor.
Timer: No.
Grid Power Boost: A heat sensor installed at the bottom of the hot water tank tells the the Paladin-2 to use grid electricity to heat water if the temperature falls below 40 degrees. Because hot water rises, this will result in the water at the outlet being above 40 degrees, which is enough for showering and general use. (In cold weather the most common shower temperature is 41 degrees.)
If the hot water system doesn’t reach a minimum of 60 degrees for 3 days it will automatically use grid power to boost the temperature to that level to control Legionella and other dangerous microorganisms.
It can also be manually boosted via use of a knob.
Special Features: The Paladin can be used to control a compatible electric vehicle charger called the JuiceBox. It does this by communicating with the vehicle charger advising it when it can charge. It does not use the diverter output. Any attempt to use variable diverter power that is only suitable for heating elements to charge an electric car would result in a great deal of magical smoke being set free.
Warranty: Its warranty is the shortest of all the diverters at 2 years. Hopefully, it will soon be increased to at least match the 5 years of the others. Paladin says none of their diverters have ever failed.
Hype: The information provided on the Paladin website is generally well grounded. This is a pleasant contrast to some of the hyperbolic claims made by other diverter suppliers.
The Powerdiverter
Price: $900 uninstalled.
Phases: Single phase.
Maximum Heating Element Capacity: 4.8 kilowatts.
Number of Heating Load Outputs: 1
Sensor Connection: Wired sensor with wireless option available.
Timer: Yes.
Grid Power Boost: Unknown.
Special Features: None that I know of.
Warranty: 5 years.
The SunMate
The SunMate is a hot water diverter supplied by Australian Wind and Solar. While the very literal-minded may think a SunMate is a sure way to get plasma burns8, it is a very interesting device because it is the only diverter that can provide 240V AC to devices once surplus solar generation reaches a preset threshold. This feature is given the somewhat unsurprising name of threshold power.
Price: $850 uninstalled for the single phase version and $1,250 uninstalled for the 3 phase version.
Phases: Single phase or 3 phase.
Maximum Heating Element Capacity: 3.6 kilowatts.
Number of Heating Load Outputs: It has two outputs which can be used as two variable heating load outputs, two threshold power load outputs, or one of each type.
Sensor Connection: Wired sensor with wireless option available.
Timer: Yes.
Grid Power Boost: A timer allows the hot water system temperature to be boosted up to three times a day using grid power. If it is set to do this in the mid to late afternoon, then provided the system gets to its maximum temperature using solar, it will be unlikely to use grid electricity. If an optional temperature sensor is installed it can boost with grid electricity until a set temperature is reached.
The SunMate also has a Legionella control function that will raise the temperature of the system to its maximum temperature, which will be at least 60 degrees, to kill potentially dangerous microorganisms every few days.
It can also be manually boosted by turning a knob.
Special Features: The SunMate has 2 outputs and these can be used to provide variable diverter power to:
- two heating elements, or
- ‘threshold power’ to two appliances (that are tolerant of intermittent power), or
- variable power to one heating element and threshold power to one appliance.
No matter what arrangement is used, the maximum amount of power that can be supplied will total 3.6 kilowatts, although this can be increased to 12 or possibly 16 kilowatts per output using optional hardware.
The ability to provide both variable power and threshold power makes it possible for the SunMate to provide a hot water system with surplus electricity and also a device such as a pool pump.
Warranty: 5 years.
The SunMate warranty states the following:
So, “This warranty will not apply” if “The product has been used and maintained according instructions provided by the company.” I find this really refreshing because it’s the exact opposite of what most warranties want you to do. But while I would like to believe they are reenvisioning the entire concept of warranties by embracing anarchy, what I think has actually happened is they have just severely under invested in the word “unless” and there is supposed to be one at the start of each of those statements.
The warranty also says that if you want to make a claim, then you have to send them:
This makes me wonder what happens if you only send them 4 good quality resolution pictures of the problem.
It also makes me wonder if the unit is prone to failures so dramatic it actually takes at least 5 good quality resolution pictures to convey the full extent of the disaster.
In these days of easy digital photography it is not unreasonable to send a photograph showing any error messages that may be displayed or damage that may be visible, but you are protected by Australian consumer guarantees and companies are not permitted to reject warranty claims because you did not jump through pointless hoops to their satisfaction.
Hype: I will force myself to only give one example of hyperbole:
My parents in rural Queensland pay 17.4 cents per kilowatt-hour for their hot water system’s economy tariff and their solar feed-in tariff is 10.1 cents. So in order to save $400 a year they would have to use 5,479 kilowatt-hours a year for heating water. That is a ridiculous amount. The average Australian family of 4 only uses around 1,500 kilowatt-hours a year for heating water. If my parents used that much, a diverter would save them around $110 a year, provided 100% of their water heating was done by solar electricity.
Diverter Thunderdome
A battle royale9 is now beginning in my brain, as I consider all the information and attempt to select an overall champion.
While I can’t actually know which diverters are the best without extended real life testing, based on the information I do have, I think I can pick a couple of winners.
Value For Money
If it is assumed the cost of installation is $300 and you just want to power a hot water system with solar electricity, then the Catch Power Green diverter with an installed cost of $1,000 and a 5 year warranty is the winner. It also has the advantage of being able to work with the largest standard hot water element.
But if you want to run a device such as a pool pump off ‘threshold power’ in addition to supplying variable diverter power to a hot water system, then provided your hot water system’s element is 3.6 kilowatts or less, you can have that option for only $150 more with the SunMate diverter. (Or a little more than $150 if the extra work of adding threshold power capability increases the installation cost.)
These two systems appear to offer the best value for money at the moment. But if you want a 3 phase system, then unless you are a really big fan of online monitoring, the SunMate 3 phase version appears to provide the best value.
My conclusions are subject to change as new information comes to light and I will endeavour to keep you up to date with new diverter developments. If you have real world experience of any of these devices, please let us know in the comments.
Footnotes
- I say we, but actually it was Jono. ↩
- Pool filters are an exception to the hardwired rule. ↩
- QLD explicitly prohibits it. I’ve been told that Tasmania allows it. My interpretation of the rules everywhere else is that it is not allowed. ↩
- A refrigeration air conditioner, not an evaporative one. Swamp coolers are very energy efficient and so even very large ones can get buy with just single phase power. Their drawback is they need water and aren’t very effective in humid climates. ↩
- Some people say electronic devices don’t actually contain magic smoke that makes them work. But if that is the case, how come no electronic device has ever continued to work after I’ve made smoke come out of it? ↩
- The Catch Power diverters can only send a maximum of 4.6 kilowatts to a 4.8 kilowatt element, but this will make no practical difference for the large majority of households. ↩
- properties on zero export that are unable to send surplus solar electricity into the grid for a feed-in tariff ↩
- As far as I am concerned, what happens between a consenting adult and a five billion year old ball of plasma is no one’s concern. ↩
- I’ve never actually seen the Japanese movie Battle Royale, but I did quite enjoy the Japanese movie Howl’s Moving Castle, so maybe I should check it out. ↩
About Ronald Brakels
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How does the SolarEdge Immersion Heater Controller compare?
https://www3.solaredge.com/sites/default/files/Immersion%20Heater%20Controller.pdf
I will definitely have to look at that and add it to the table. Thanks for mentioning it, Anton.
For those with an existing Fronius inverter (with/without Smart Meter), they can also look at using the energy management relay function.
Maybe you can put that in as well.
Covered it recently here:
https://www.solarquotes.com.au/blog/using-fronius-inverter-smart-meter-relay-make-solar-electric-hot-water/
While not a diverter it is definitely something to consider when it comes to heating water with solar power.
Yupe.. Saw your previous post.
I was suggesting adding it into the table for completeness.
Hi Ronald,
I installed a SunMate on my folks system and they have only had to boost their hot water system once for 2 hours (in dead of winter). The product works very well. They have not had to pay for off-peak grid electricity for 9 months since it was installed.
It helped maximise the use of their 5kW system and improves their self-use consumption ratio by about 15% in the last 9 months.
Their off-peak rate is only 6c cheaper than normal rates (Ergon), so it paid to have the hot water power diverter.
On another note, Dimplex have a product called Free-E. Dimplex RRP is $999 but this could be different at retailers (Turks, L&H, Reece).
Regards,
Graham
Just further info on Ergon off-peak rates, it’s now 22.5c/kWh on T33 tariff (1/7/2017 price) (18 hour rate). So, on $400 savings is about 1777kWh of hot water heating required So, that’s not suprising.
100 litres of hot water to be raised by 45 degrees per day requries about 5.25kWh of energy.
That at 365 days is about 1900kWh.
That’s about 2 hot showers per day. Let alone, anything else needing hot water like washing. Plus any heat losses from Hot water.
So, $400 savings is not really hype.
Ergon’s tariff 31 is 17.4 cents a kilowatt-hour and the feed-in tariff is 10.1 cents. So every kilowatt-hour diverted from being sent into the grid to heating water will saving only 7.3 cents. With 1,900 kilowatt-hours annual use that would come to a total saving of $139 provided all their hot water was entirely heated by solar electricity.
Tariff 33 costs more but is provided for a minimum of 18 hours a day instead of 8, so if tariff 33 is required for the current hot water system to provide adequate hot water then if it put on a diverter it is likely to also need a considerable amount of grid electricity for heating. But even if this hot water system could be entirely solar powered it would only save $236 a year if 1,900 kilowatt-hours of tariff 33 electricity would otherwise have been used.
While there are definitely families that use over 1,900 kilowatt-hours a year for heating water, most use much less than this, especially in rural Queensland where Ergon operates, so I have no problem describing a claim of $400 of savings from using a solar hot water diverter as being hyperbole at best.
I will have to look into the Free-E Dimplex and see what it is like.
I do remember once meeting someone from PowerDiverter who was very much a salesperson… I believe they were a UK company trying to launch in the AU market – but had not really gotten their head around the differences in the AU grid… That would have been at least 2 x years ago – so if they still haven’t gotten the product right and are uncontactable, maybe they gave up!
Hi Ronald,
How did you calculate 5749kWh on $400 at 17.4c/kWh?
By my calculation… $400 at 17.4c = 2298kWh required to offset the off-peak tariff rates.
Granted, that’s a lot of hot water to heat, but that 2298kWh equates to about 120 litres of water per day requiring heating from 20C to 65C. That’s about 12 minutes of hot water running (assuming 10litres/min) but more likely 20+minutes with cold water mixing at tap. Obviously, if the water is colder than 20C, then more energy required to raise the temp. Or, if you wanted 70C water in the tank (definite instant kill for legionella), more energy required again. The hotter water will keep it’s heat retained longer to overcome less sunny days which I set my parents tank to so that cold water coming into the tank doesn’t reduce the temp as quickly if the tank was set to 60 or 65C. (Yes, I know that there is a formula for working out mixing water of diff temps to get final water temp). Getting free energy, so what not use it to raise the water temp a bit higher.
PS> water tempering valve drops to “50C” mark, so some say it’s wasting energy to heat water to 70C but there are other good reasons for water heating to 70C (if you do not have a solar hot water system). e.g., legionella control and heat retention is longer.
Graham, If I have a choice between sending one kilowatt-hour of surplus electricity into the grid for 10.1 cents or diverting it to a hot water system where it will displace 17.4 cents word of tariff 31 grid electricity, then by diverting it to the hot water system I will only come out 7.3 cents ahead. That means to save $400 in a year I would have to divert 5,479 kilowatt-hours.
My parents, who have tariff 31 in Queensland, used 232 kilowatt-hours over the last quarter which was mostly in winter. Even if they used that much in summer as well it would only come to 928 kilowatt-hours. While there are definitely families that use far more than this, it is definitely not typical.
I would suggest including the Fronius inverter that has a threshold relay. Ok sure it’s not really a “diverter” as such but claims to do exactly the same job. ie heat hot water using excess solar electricity that would oterwise have been fed in to the grid.
As i understand it you set the relay to operate when feed in/excess solar energy reaches the desired level. Its not clear to me if the relay can work with off peak or controlled load where feed in (excess) has not reached the set point on a particular day.
Recently covered it here:
https://www.solarquotes.com.au/blog/using-fronius-inverter-smart-meter-relay-make-solar-electric-hot-water/
G’day Ronald, I understand Fronius will release their own diverter soon enough, called the ‘OhmPilot’
The Fronius OhmPilot is available in Europe and I wouldn’t be surprised if they have been testing it in Australian conditions prior to selling it here. It’s not cheap in Europe I am afraid, but they may give us a good price.
Hello, this comment is not related to power diverters, as interesting as they are.
Couldn’t figure out how to write to you directly, so leaving a comment here. Just wondering if you have had a look at Suntenants in Sydney. As a landlord wanting to install pv on the rental, this is an interesting approach. Just wondering what your view is – particularly if considering installing a larger system intended to export most of it output.
Love your writing style. Adding amusement to an otherwise dry subject!
Hello Paul.
I haven’t looked into SunTenants, but I have written about Matter which sells rooftop solar electricity to tenants:
https://www.solarquotes.com.au/blog/solar-for-renters/
Looking at the SunTenants site I am afraid there is not enough information there for me to understand what they do. Since they haven’t given me enough information to form an opinion I’ll ignore them for now. But if you uncover interesting information, please don’t hesitate to inform me.
A suggested small correction – in the above article, is
”
Single Phase or 3 Phase: Most homes have single phase power, but an increasing number have 3 phase. If your home has a large ducted air conditioner that serves multiple rooms there is a good chance you have 3 phase power.
”
I suggest that the text
” If your home has a large ducted air conditioner”
be corrected, by inserting the word ” refrigerative”, so becoming
” If your home has a large ducted refrigerative air conditioner”.
Reason – we have a large ducted evaporative air conditioner, which does not require three phase electricity supply, and so our house has single phase electricity supply.
Good point. I’ve added a note mentioning this.
Ronald, if the surplus power is fed to a resistive heating element, then it’s no big deal for it to switch in and out as clouds go over, but if there’s a heat pump in between, then there’s the same “starting the compressor on load” problem as with an air conditioner. So I can’t help wondering if any of the (AC output) diverters have a cycle timer to set a minimum off time after cutting out.
I figure that with a system with battery, I’d be able to bridge a cloud or two with battery power, and the lower heat pump consumption will be much less of an issue.
Yep, devices that provide threshold power have various timers that can be set, generally including minimum operating time, delay before turning on after the threshold is reached, and delay in turning off after surplus solar electricity falls below the threshold amount.
(Asking three years later) – does this mean that I can still hope to have a diverter with my newly installed Sanden 315L heat pump HWS?
Unfortunately, heat pumps can’t run off the power a diverter provides. But the good news is every heat pump hot water system should have a timer that will let you set it to turn on during the day. This will turn it on when solar power is being produced and because a heat pump hot water system doesn’t draw much power it should mostly run off solar power if your solar system isn’t tiny.
I’m in Melbourne. My background is IT technical, and I’m retired. I installed a 4.8 kw system in Feb based on information such as you are providing. The reality is that the actual does not reflect the reality. In summer the system does generate a reasonable output, but in winter, unshaded, and facing north, the output is minimal. Had I known the reality, I would never have gone solar. I have a two rate smart meter, monitored by a Pipit500 so that I can read the meter remotely.
Until a month ago my rate was around 32c peak and 22c Offpeak (Ausnet). The best discount I could get was 38% on usage. If I elected to use the feed in tariff which was 5.8c per kWh, my discount would have dropped to around 14%. You don’t need to be too bright to figure that applying for a FIT would result in an increase in cost, not a saving.
Given the cost of installation, added to which the removal of some trees, and the nightmare of having Goodwee fiddling with the inverter setting to stop the unit thinking the grid voltage was at least 280v, the basic system as described was misleading. In terms of diverting power to an offpeak HWS, these theoretical essays of yours are fantasy.
They certainly do not apply as a realistic investment in Melbourne. As someone now retired, who has spent a lifetime project managing large electronic installations, I suggest the complexity and cost of getting an experienced professional to install and maintain any of the diverters for a normal user is far from the picture you are painting.
Great for early adopters who philosophically feel they are saving the planet, but until solar costs reduce in cost and installation complexity, the cost/benefit ratio does not stack up. As someone who managed and architected projects up to several hundreds of millions of dollars, I am aware that many things are technically possible, but the reality is that for most people implementing your suggested solutions would not only be non-viable, but turn into a nightmare due to the difficulties of finding knowledgeable qualified technical implementation and support.
The major issue, I have found, in practice, is that the electricity wholesalers, actively discourage solar by restricting the size of units, and paying 5.8c kWh which they then sell at 44c per kWh to your neighbour.
Hello David.
Sorry to hear your solar system isn’t performing well. In Melbourne in June, which is the worst month for solar, a 4.8 kilowatt north facing system should be producing an average of around 11 kilowatt-hours a day. If it was significantly less than this you may want to contact your installer and let them know it hasn’t been operating as it should.
Hey David, Please don’t denegrate the great work that Ronald is doing – its really hard finding all the different makes & models suitable for your requirement & Ronald is conveying a needed message to those not only in the know but the uneducated (on this subject) as to reasonable paths to follow if they wish to use solar energy as a power source.
On the subject of water that is hot enough to shower, I/we (2 of) here in Port Macquarie have the greatest system (In my mind).
It is a 30 tube SHWS, 250l 3.6kW, SR208C SHWS controller (with its timers & temp control), a http://www.mk2pvrouter.co.uk/ (home made – is controlled by SR208C, controls pump, gives me a display of export/import power, 6.4kW PV(in reality about 4-5), can control >5kW (24kW triac))
I need only to boost a few days a year, so I have ridded the meter box of the CL1 meter & relay.
I reckon I am going to save-wait for it about $150 per year not much in the scheme of things but I know the energy is not coming from anywhere but the sun. Cost me about $300 installed (me-tech & sparky mate)
Ronald – Love your blog.
You could also look into the Solic 200. Available in Australia for $399 uninstalled. Looks like it has great possibilites as a very good price
Hi,
I have decided that a solar diverter is the best way to go for me as I currently export to the grid most of my solar energy (even when I set Dishwasher and washing machine on timer delay).
So this article is great. Keep up the good work.
One question that hasent really been spoken about is the advantages/disadvantages of the control method (phase angle, burst etc) Is one better than the other for efficiency, energy calculations, electrical noise?
Also, do all diverters send whatever they can to the element whenever they can. For example, is it ok to just send 200W to a 3.6KW element?
It also seems that only one product allows you to monitor operations from a website, but that product seems very expensive.
I had an Immersun installed for two years up until today when it literally went bang and lost all its magic smoke. No chance of a warranty claim or even help so I’ve googled and found this helpful article. I just did my sums – I’m south of Sydney on an Origin plan that includes a 18% discount on usage, so my effective cost with discount per kW/h for Off peak power is 9.43 cents.
I get a 9 cent feed in tariff, so my saving is only .43 cents or an approximate saving of around $9 per year based on my usage.
Based on a $9 saving, it will take too long to recoup my costs for any diverter … now I’m kicking myself for forking out $1k two years ago for the Immersun as the UK company that bought them out doesn’t want to help, other than sell me a new one.
My take-away from this is that even if the company offers a 5 year warranty, it’s no use if the company has gone out of business or has phoenixed.
Hi,
Great article. Your comment that “Australian family of 4 only uses around 1,500 kilowatt-hours a year for heating water.” is probably too low. It’s more like 4000Kw per year based on personal experience.
Hello
There is a lot of variation between different parts of the country and households, so I think the figure I used is roughly correct. But if I come across solid evidence the number I used is too low I will update the article.
I have to concur with Brad… 1500kWh is a low number for hot water heating.
Based on the following assumptions:-
Cold water in at 20C
Final hot water at 65C
Delta is 45C
Water heating specific 4.18
1kWh = 3.6MJ
So, 1500kWh = 5400MJ
Energy required to heat water = 4.18 * 45 * Mass of water (in grams).
Working backwards, Mass of water = Energy / (4.18 *45) / 365
to get daily water used in total
=5400000000/4.18/45/365
= 78652 grams
= 78 litres/day
4 people = 19 litres of straight hot water at 65C per person per day
Dliute with cold water to 50% brings to roughly 38 litres.
Mains water flow at 10L/min for a decent rain shower (none of that water saving devices rubbish as it takes longer to rinse out soap/shampoo).
Brings us to a 4 min shower/per person/per day. Wow, that is really penny pinching it!
Nah, the real world is about 10 mins in the shower. For some people, they even take 20 mins. In summer, cooler showers usually prevail and in winter – hotter showers, so, on average, the whole year balances out in hot water usage per day.
So, for 10mins = 100 litres water used, 50% hot/cold brings us 50Litres of hot water, which is 50,000 grams.
Back to the energy formula brings us:-
Energy used = 50000 * 4.18 * 45 * 365
= 3432 MJ per person per year
Family of 4 = 13728 MJ required to heat water from 20C to 65C.
In kWh terms, this translates to about 3813 kWH (assuming 100% efficiency), so essentially the 4000kWh is pretty close to the mark that Brad says.
Now, this only applies for bathing purposes only. Let’s not forget that there’s dishwashing (mine is connected to hot water directly, so the dishwasher does not heat the water using peak rates!), then there’s clothes washing. A warm water wash is way better than cold water wash. Detergents work better at warm water wash, which means less harsh chemicals are required in the cold wash which means it’s better for the environment.
Which is why Solar Hot Water and Heat Pumps are essential if one wants to reduce the amount of energy required to heat water!!!! Heating water is an energy intensive process. Most people don’t realise this. It’s just fortunate that if we have off-peak rates to offset the energy costs for heating water. Imagine if we didn’t have off-peak rates? People would be compelled to find the most economical way to heat water. Firstly and obviously – using the sun to do most of the work. Using excess PV energy diverted to heat water is one of the best way to do it, since off peak rates are now between 12c and 35c per kWH. FiT is around 12c (in NSW). So, unless your off-peak rate matches FiT, then best to use your excess PV electricity to divert to hot water system.
The physics don’t lie……
“But the lower temperature set point should be at least 60 degrees to control the growth of Legionella”
According to the cited https://en.wikipedia.org/wiki/Legionella :
“At 50 °C (122 °F) – 90% die in 80–124 minutes, depending on strain (Decimal reduction time (D) = 80–124 minutes)”
i.e, at 50 °C there won’t be growth of Legionella numbers but decay so unless your cold water supply has a problem with Legionella, you won’t have a problem with Legionella in your hot water.
Great article ? my gas heater is getting old and i now have 40 solar panels on my house in Whyalla getting lots of sun and Origin 18c feed in tariff. I’m seriously looking at getting a 315L electric hot water heater and running it exclusively on a solar diverter. House is 3 phase and solar is 2 single phase 5wk systems. Not sure which diverter is the go ? need to research ?
Has anyone got Solahart power store australias first solar smart electric water heater…. big bucks
Be good if the webpage was included to make it easier for others to find.
https://www.solahart.com.au/landing-pages/energy-storage/
Yes, the Solahart PowerStore Hot water system is $3395… pfft – what a rip off. You could get a proper solar thermal hot water system for that price.
All they did was slap a control box on the side.
Way cheaper to buy a standard 315L Hot water tank for less than $1000, use a device like the SunMate Power diverter for about $995 or equivalent product. Less than $2000 to do the same thing. Which is what I did for my parents. They have not since used any off-peak power to heat the water for 2 years now. Only 3 times (in Winter), they had to boost it at night using normal tariffs for a total of about 12 hours.
Good concept to integrate everything into one unit though but the price needs to come down more realistically to around the $2000 mark or below to make it competitive.
Granted, it has a smart app for real time monitoring which would be handy to see what’s happening but not enough to justify its cost, too expensive at this stage.
The reason that Solahart developed the PowerStore is because they consider that almost all solar diverters are not compliant with Australian Electrical Safety Standards.
This view was validated by the Electrical Regulatory Authorities Council
https://www.erac.gov.au/wp-content/uploads/2019/12/ERAC_Information_Bulletin-0022-Solar_Diverter_Dec2019.pdf
As a result most Australian hot water manufacturers will deny any warranty claim for a failed hot water system where a solar diverter has been attached.
The above bulletin says no such thing. It merely outlines some of the requirements for solar diverters.
Can you name one model and brand of HWS in which the warranty conditions state that it must not be connected to a solar diverter or the warranty will be void?
Even if it did state that, the warranty is mandatory under the Australian Consumer Law. There is no provision within that law for a manufacturer to deny a claim for such a spurious reason, unless the manufacturer can prove that an intermittent supply (burst mode, pwm etc) can somehow damage a resistive element, which in fact it can’t.
Hi Ronald et al,
Thanks for this blog. Note it’s now 6 years since this blog was published so wondering if you still recommend the 2 diverters mentioned at the end ?
I’m needing to look at diverting excess solar to hot water.
I’ve got electric control load 2 – I’m not sure how that works but think it runs 24 hrs Keeping water hot. Please correct if I’m incorrect.
I’m with Origin. New rates are 20c CL2 and FIT 10c for first 14kw and 7c per kWh after that.
Hot water accounts for 50% of usage I get billed for. I pay monthly. Eg. 450kwh CL2 and 450kwh by TOU. I average 15kw export daily .
I had my 6.5kw solar installed Feb 2019. REC panels and Fronius 5kw inverter. I also have Solar Analytics which has calculated my savings since installation and shows that as per prediction at the time, after 4.5years years I’m now break even with the investment cost (ie. (Savings now at the $10k cost).
I would appreciate very much your feedback about best diverter in 2023.
Also from anyone who has installed diverter and how it’s going.
Many thanks.
I went through 3 heat pump hot water systems in 16 months. Over a couple of warranty fixes (that didn’t last long), the final replacement lasted just long enough to take me out of its warranty period, then karked it completely.
Not at all impressed, seeing I brought a ‘brand’ name, under the naive assumption that I’d get ‘quality’.
Like Graham, I came to the conclusion that a no-frills standard 315 litre system was the way to go, and had a relay switch added to my replacement PV system. The best measurement of average power consumption I can come up with for the water heater is 3.5 KWh a day. It’s rated power consumption is 3600 watts and the heater unit only has a single element located at the bottom of the tank.
The exterior brass fittings (the hot water outlet pipe and the safety release valve) both radiate a LOT of heat, so when installing it, I had the outlet pipe insulated for most of its visible length to lower its heat loss. Its difficult to properly insulate the safety release valve though because of its shape
A friend of mine has a solar hot water heater that uses evacuated tubes, and its electricity consumption for a whole quarter is just 1 kwh, but you can’t really justify the upfront outlay.
I had a solar water heater on my previous home which worked OK, but ‘repairs’ are a problem, especially so if you have a double storey high-set home. Nor do I like the idea of having roughly 400+ kilos of water and tank and panel weight spread over a very small area on my roof. With newer homes, if you are not very careful about placement and what actually supports that weight from underneath in the interior roof space , you can unwittingly exceed the overall weight load that’s permitted, especially so if your roof also has rather clay tiles.
Personally, there’s no way I’d ever put a very heavy water tank on my own house roof – a bad storm, underlying timber frame and truss deterioration over time, possibility of water leakage that takes out your plastered interior ceilings, slightly substandard fitting by a busy plumber and maybe just one fitting springs a leak and starts slowly dripping, eventually causing ceiling mould and general dampness problems . All sorts of minor things can ‘go wrong’ and they usually do, By the time you find out about it the expense of fixing the end consequences can be huge.
although you can get around that by putting the tank on the ground and also fitting a small electric pump to circulates the water between the tank and the roof.
I have just run into a potentially expensive problem with a blue catchpower 3 phase diverter. My meter box is 50 metres from the house where the panels and 3 phase inverter are. I have no separate J Tariff meter so there is no independent feed to the house. I have already bought the 400 litre storage HWS. Now the installer tells me that one blue box needs to be installed next to the meter and needs a separate feed to the HWS. This has just blown the exercise out of the water. Hopefully I can return the catchpower to the provider. The provider was very confident it would all work, but I now realise I should have insisted on a site visit before signing up.
That’s unfortunate. But the good news is, if Catchpower told you it would work and it won’t under Australian Consumer Law they are required to give you a refund. Clearly this is something to watch out for.
I seem to be struggling to get any independent info on these diverters. I need a simple (ha ha) 3 phase diverter that will work wireless from the meter box 50 meters to the distribution board where a new designated circuit for a 400 litre HWS storage tank will run from. I would gladly ring the agents/manufacturers direct, but is this the best way to an outcome ? Is there any upgrade on the diverter comparison eg. is the catchpower green now available in 3 phase ?
Hi Kerry
Catch Power says their Catch Power Green will work with 3 phase homes, but not as well. It will only divert power to the hot water system when it detects power being exported to the grid through the one phase its CT sensor clamp is connected to and it won’t divert more power than is being exported through that phase. But if you have a large enough solar system it may work acceptably. You’d have to contact Catch Power to ask them if it’s practical.
Hi Ronald,
Another interesting comparison for the HW Diverters is the minimum amount of export before they divert power to the HW cylinder. Do you have those figures for the different models? I’ve heard variations of between 50W to 250W.
I afraid I don’t have figures for the minimum amount of export required. About 100 watts may be typical. This can add up to more than 1 kilowatt-hour that could have been used to heat water being exported to the grid. It is likely to never be spot on as long as CT clamp sensors are used. (Needing a minimum export level before charging or discharging is also a problem battery systems have.)
Hi Alan,
My parents’ SunMate that I installed starts to divert power to the hot water system once exports to the grid goes over 50W, so it’s something interesting to watch.
It’s pretty accurate.
In regards to CT clamp sensors, it’s only inaccurate if it does not measure the voltage. (like many energy monitors do, they only sense current – so they can be out by as much as 30% because the software assumes a nominal voltage of 240V – but voltages can vary between 216V to 252V). Which is why they are cheap ($100-$150). A true power sensor needs to measure both voltage and current and they cost over $250 minimum. Which is why I was annoyed with my first energy monitor (Wattson/Holmes package). I tried Efergy, it was worse, I sent it back and got a refund. Now that I have my Powerwall – it has revenue grade metering (1% accuracy).
The SunMate is hard wired so it’s already sensing the voltage and combined with the CT clamp sensor, it can work out the the true power based on the voltage and current.
The problem with battery system is the reaction time for the system to determine how much to discharge/recharge without triggering too much grid power (both import and export). It takes a few sinewave cycles about up to 1-2s for the Tesla Powerwall battery system to correctly adjust to the demand required. It’s not instantenous. To have a system that can respond instantly would be cost prohitive to implement just to shave a second or so of impulse power to be met by the grid while the battery discharge catches up. Not worth doing. Loads are constanly flip flopping. The worse load I have noticed is the washing machine motor as it agitates. You see this constant export/import occurring as the battery tries to match the load impulse each time the motor draws power which is about once every 2 seconds in the agitation cycle, while it’s spinning – it’s smooth. I guess I can see the advantage of a inverter motor in washing machine now for smoother draws rather than the large crude in-rush current draw that motors are known to do. So, at the moment I won’t be rushing out to replace the washing machine when it comes time to replace it I will get a washing machine with an inverter drive. The fridge and air cons already have inverter motors so they run smoothly.
Hope this is of some help
Hi Ronald, I have had a Catch Power Blue diverter for five months and overall it does a good job heating water. My issue is that it does not seem to use only “excess’ energy. My data from Powershop shows that after the PV system was installed and before the diverter was installed, there were many periods during the day of little or no import from the grid. After the diverter was installed, there are many more periods of drawing from the grid and at much higher levels. It seems as if the diverter is sending solar power first to the tank instead of to the house. Except for some short instances, the system is constantly drawing from the grid throughout the day until the water in the tank is hot and the tank’s thermostat cuts in. Then we stop importing from the grid. Sometimes daytime consumption is high and constant, despite power going to the hot water tank at the same time. If the diverter was using only excess power then it would use only power left over after house power.
It’s a mystery. Can you help please?
Hi Victor
I’m afraid I don’t know what the problem could be. There could be an issue with the sensor clamps that detect current so it may be worthwhile checking if they are all connected correctly and the right way around. It’s also possible its settings may be wrong. I suggest getting in touch with Catch Power or whoever installed it and they should be able to help you. (It has a 5 year warranty.) If you have trouble getting in touch with Catch Power I can forward a message for you.
Are there any solar diverters capable of handling loads for under-floor heating of 24kW and 100A?
Not that I know of but 24 kilowatts is a huge load. It’s probably enough for over 200 square meters of flooring.
My problem is that I fitted a SunMate PV Diverter through a standard non-smart power meter about 2 years ago. The diverter worked fine for hot water system power. However, recently I had to have a smart meter installed as part of a Sonnan solar battery installation and the Sunmate was not compatible. Apparently it’s to do with the sampling rates. The result was that the smart meter was flipping between export and import about every second resulting in a typical daily figure of 4kwh export at 16.3c/kWh and 4kwh import at 41c/kWh.
Sunmate don’T want to know and their latest Sunmate specs suggest this unit is still not compatible with smart meters (eg sampling every 2 secs). Other units available in Aust do not Indiicate if their units are compatible wth smart meters, so it’s BUYER BEWARE.
I wonder please about the New Zealand market?
We had various and ongoing issues with the Iboost and are now on the search for an alternative unit.
Any ideas or guidance appreciated. Thank You
I presume you are in NZ. I wrote the post above. I replaced the Sunmate with a Palladin Diverter which is compatabile with the Aust smart meters and I am very satisfied. The paladin unit samples at 3000 times a sec and tracks the available excess solar being exported very accurately. I have it fitted in conjunction with a Sonnen battery system and is configured to operate after the battery is topped up. I suggest you google Palladian and contact the owner who is very helpful. If your power meter has comms to the power supplier it will probably be a smart meter but I see no reason why it should not be compatible with a non smart meter.
Paladin phone number in Aust is tel:0416245439. You may need to add Aust code if in NZ. Also try and identify meter type.
I checked and that’s the number Paladin have on their site.
I would endorse the praise for Palladin . The guy I dealt with didn’t try to sell me the diverter, when he realised that it wouldn’t suit our 3 phase set up. Went out of his way to do the research and followed up when he said he would. A pleasure to deal with someone with integrity.
Thanks Kerry, we will keep it in mind
Hi Ronald
We have an off grid system in the eastern Mount Lofty Ranges and have a Beasley roof master HWS in the roof. The original system was connected to a wet back on our Nectre stove and 2 Solar HW panels. After replacing many panels due to frost damage we have finally disconnected and removed the Solar HW Panels. What I plan to do is to install more PV panels (Maybe 5kW) and use a diverter to feed power into the HWS in Summer. In Winter the wetback is more than sufficient and I plan to manually switch the new panels to boost up my existing 2.4kW system. So for six months the new PV panels heat the HWS (over summer), and during winter provide a power boost to our existing off grid system.
Can I use a diverter in this scenario. The Beasley has a 3kW element installed, but never used.
Rob
Hi Rob
That should be no problem. You just need to check the diverter is suitable for your situation. It should be fine with the element in the Beasley hot water system.
Thanks for you response. As I get closer to a solution I will keep you updated. There are many users out there in ‘frost’ country that have tried the HW solar panel option with disappointing results. I think the providers of diverters have a large ready market. I have never heard of frost affecting PV panels! Which is probably a good thing for people designing and building working space craft and satellites.
Rob
There is a new power diverter available in Australia….
It’s called eddi from myenergi
https://myenergi.com/product/eddi/
There is an Australian distributor…..
https://evolutionaustralia.com.au/product-page/myenergi-eddi-energy-redirector/
Looks like a nice looking unit with a neat graphical display screen.
There’s even a Youtube video of an Australian installation (the same guy who built his own “Powerwall”.
https://www.youtube.com/watch?v=VbTWK6kL7L0
No information about sampling rates as this now seems to be an important factor with smart meters.
I had a Green CatchPower unit installed March 2018 after the removal of my Controlled Load meter as suggested by the installer and as also suggested in CatchPower’s promotional material.
It took some time to realise that when there was less surplus solar energy to feed the 3.6kWh HWS element, that the shortfall was drawn from the grid which was then immediately fed back into the grid. CatchPower explained that due to the inefficiency of the power meter, that it would not see this power being rapidly drawn from and then fed back into the grid. However, with my ‘smart meter’ this has been found to be incorrect and the meter is actually seeing ALL power drawn / fed into the grid.
The result is that whilst I am drawing less power from the grid, the cost has actually increased because some of the power drawn from the grid to reheat the HWS is during daylight hours at the Peak / Shoulder rates compared to the previous Controlled Load rates.
I also have a battery storage system and I suggested that any shortfall be drawn from this system rather than from the grid bearing in mind that once the battery storage fell below 100%, no power would be diverted to the HWS until 100% charging was again restored. In addition, whilst any night time boost to the HWS would be drawn from the battery storage, this would not be a problem as it was programmed to draw power from the grid to maintain a minimum of 15% charge. However, when wired this way, it was found that CatchPower diverted ALL available power to the HWS; not just the surplus solar power.
CatchPower have offered to remove the unit and provide a refund but this will not overcome the issue as the Controlled Load meter has been removed as explained above.
Does anybody know of a diverter that only uses the actual surplus power available rather than flicking power to / from the grid?
Ref my post of Feb 9 19 and May 01 19. I had this exact problem when I had to change to a Smart Meter when installing a Sonnen battery. I had a Sunmate fitted on the dumb meter which worked fine, but was not compatible with the smart meter for the reason you state. I also tried the CatchPower unit but it was worse for compatibility than the SunMate.
I fitted a Paladin unit and although there is a very slight draw/export effect it is absolutely minimal. On my monitor it is showing a mains draw of approx 50 watts at full 3.6kw draw. It allows the battery to top up first and then loads the HWS. When charging the battery, if a heavy load such as a 2.4kw kettle is run it will occasionally temporarily switch power to the HWS after the extra load is removed but this only lasts several minutes before resuming battery charge. I have found the Paladin unit to be very satisfactory overall.
Hi All,
Does throwing in a battery pack in WA make any difference in considerations?
From a Dummy
Vic
Not at the moment, I’m afraid. While WA’s unfairly low feed-in tariff brings home batteries closer to paying for themselves they still won’t save any remotely normal household money at this time. Of course, batteries can still be bought for reasons other than a financial return.
But if an electric hot water system is installed they can be used to heat water during the day for use later, allowing energy consumption to be shifted to the day.
Thank you.
Keep safe.
Vic
This article discusses the effects of a diverter on power quality and the accuracy of metering. An interesting read. Perhaps they aren’t such a good idea!
http://www.drmartingill.com.au/wp-content/uploads/2018/01/Solar-Diverters-v02.pdf
Martin seems well qualified to write this article.
A 3.6kw element being switched on/off rapidly is a lot different in scale to a light bulb on a dimmer so it can really mess with the power meter especially the newer smart meters.
An inexpensive solution to heating the water with solar and forgo 3c/kWh feed-in tariff in WA is to buy a Fronius inverter like my Symo 5kW one. Those models contain a Datamanager board, which can be set to drive a relay to switch on the H/W element based on production, not surplus. What can be set is:
1 Watts supplied to switch on, (2500)
2 Watts supplied to switch off, (2000)
3 Minimum run time, (1 minute)
4 Max. total run time, (6 hrs.) and
5 Switch off time, like 5PM
The element is a 2,400W one.
Fronius is also selling a Smart Meter, which works out the surplus left over from import vs. export, but the extra $1,000 may not be worthwhile. Even more expensive is the Fronius Ohm Pilot, which uses Pulse Width Modulation to feed the H/W system. Every Fronius agent wants to sell the Smart Meter and is not interested in installing the relay to connect the H/W system to the Datamanager board, which outputs a 12VDC signal for a relay.
An electrician then installed a WiFi relay into the H/W supply. With the Fronius Solarweb app I can look at the PV supply and knowing what is running in the house make a judgement when to activate the H/W system via the Gridconnect app for the Arlec WiFi relay with smart meter.
Not convenient during cloudy days as the supply is intermittent, but I hope a WiFi signal can be sent from the Fronius Datamanager card instead.
You say at the start of the article:
“Devices on controlled load or economy tariffs must be hardwired. They cannot be connected to any other power source except the controlled load/economy tariff meter. So a hot water element connected to solar via a diverter cannot also be connected to a controlled load or economy tariff.”
That is also my understanding, at least here in NSW, but my question is WHY??? I spoke to two level-2 electricians recently and they had no idea. If installed properly there are no safety issues, so is it just greedy electricity retailers seeking to maximise profits at customers’ expense by preventing them from using controlled-load power overnight and solar during the day?
What are those in the industry (such as yourselves) doing to lobby governments to have this archaic and restrictive bureaucratic nonsense overturned? We constantly hear about problems with feed-in and the desirability of self consumption, yet that regulation make one of the most obvious and cost-effective methods of self consumption illegal.
Cost recovery for solar diverters costing up to $2K is unlikely to occur before the warranties expire so I don’t see them as viable. Simple timers often end up costing money if they switch on when there is no spare power being produced meaning they draw from the grid at peak rates.
The simplest and cheapest solution, especially for retirees who spend most of their time at home, would be to install a SPDT contactor on the live side of the HWS breaker, for example https://www.sparkydirect.com.au/p/Hager-ESC227-25Amp-2-Pole-Contactor-240V-1-N/O-1-N/C
One input would come from the controlled load 1 supply and would get switched on overnight. The second input would be from a regular circuit (ie solar when available).
There would be a simple push-button timer switch in a convenient location inside the house, for example https://www.sparkydirect.com.au/p/Clipsal-2031VETR-Electronic-Time-Delay-Push-Button-Switch-Series-2000
On sunny days when not doing the washing or cooking dinner, the homeowner would press the switch. It would switch the contactor over to turn on power to the HWS for a preset time (0 – 4 hrs) to heat up the water from solar then turn off again. it is no more complicated than remembering to take their heart medication each day! If they forget or it is cloudy the water will heat up from controlled load power overnight.
For dual-element HWS units both elements would be wired in parallel. The HWS circuitry only allows one element to work at a time. The HWS would thus decide whether to heat the entire tank or just the top half, exactly as it does overnight at present when the boost element is permanently powered and the controlled load switches on power to the bottom element.
The purpose of the requirement that devices on controlled loads be hardwired is to prevent them from being used during periods of high demand and so shift electricity consumption to low demand periods. The goal is to reduce the amount of money that needs to be spent on expanding grid peak capacity. Generally, Distributed Network Service Providers won’t allow workarounds.
That reason may have made sense when the only alternative source of power was peak grid power. It make no sense these days with the availabily of solar power. In fact the regulation is now increasing peak demand.
As more people install solar more and more HWS units will be disconnected from controlled load and connected to a standard circuit. That means they will now be running at peak times whenever it is cloudy or the house is using all available solar power, whereas in the past they would have been powered overnight only.
Even without solar it makes no sense, given that any HWS can lawfully be disconnected permanently from controlled load and connected to peak power. I therefore do no understand how running it briefly from the grid during peak periods, in addition to overnight, should have been an issue.
With the help of an electrician friend we have finally changed over from our expensive LPG gas instantaneous hot water to an electric boosted solar hot water system. We probably wouldn’t have gone down this path ,but for bad advice. When we ordered our solar PV system 3 years ago we ordered a solar diverter. However due to the provider not doing their research nor an inspection prior to installation , we couldn’t fit the diverter ,due to having a meter box remote on our shed ,no designated hot water line from the shed to the house and 3 phase. We also bought a new 400 litre storage tank at the same time. I am not a fan of heat pumps so that wasn’t an option.
So we decided to get 2 roof mounted hot water panels and the circulation pump/controller. We managed to get a 1200 W element for the tank. The electrician then wired up a separate circuit for the HWS with a din rail mounted timer in the switchboard set to run from 10.00 am to 3.00 pm. AGL now offers a solar sponge rate of 21c/kwh during this time period ,so not too expensive if we do draw power from the grid.
We also set up a further system inline to utilise the excess from the solar PV panels as much as possible.This system is a poor mans diverter and cost less than $100. It consists of an adjustable light control sensor feeding a normally closed contactor with a switch to over ride the light sensor if needed. The light sensor only has 0-500 lux range ,so was set up to only get indirect daylight. We were then able to adjust it so that it opened the contactor IE shut the element off , when the PV panels were putting out roughly 1800W or less
It is working very well , obviously if you switch the electric jug or something else on ,you will temporarily draw from the grid , but overall a very cost effective alternative to a diverter etc. If we were doing it again we probably wouldn’t go as low as as a 1200 W element. A 1500 W or even 1800 W element would have better covered the few heavily clouded days a year when you get no input from the solar thermal panels.
Are there any recent comprehensive reviews on solar hot water diverters available in Australia or plans to do an updated version of this article?