{"id":14165,"date":"2017-08-22T17:19:43","date_gmt":"2017-08-22T06:49:43","guid":{"rendered":"https:\/\/www.solarquotes.com.au\/blog\/?p=14165"},"modified":"2024-10-02T12:16:40","modified_gmt":"2024-10-02T02:46:40","slug":"solar-hot-water-diverters-vs-batteries","status":"publish","type":"post","link":"https:\/\/www.solarquotes.com.au\/blog\/solar-hot-water-diverters-vs-batteries\/","title":{"rendered":"Solar Hot Water Diverters Beat Batteries On Energy Storage"},"content":{"rendered":"
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If you want to store your solar energy, should you put it in a battery or in your hot water cylinder?<\/p><\/div>\n

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Update:<\/strong> Compare all the hot water diverters available in Australia here.<\/a><\/p>\n

How A Diverter Can Give You Solar Hot Water And Store Energy At A Lower Cost Than Batteries<\/strong><\/p>\n

A solar hot water diverter is an electronic device that sends surplus electricity from your rooftop solar to your electric hot water cylinder.\u00a0 This reduces, or even eliminates, the need to use grid electricity to heat water. \u00a0Under the right circumstances diverters can save you money and allow you to store energy at a cost lower than batteries.<\/p>\n

Diverters work with standard electric hot water systems that consist of a storage tank with an electric heating element inside.\u00a0 These are common in Australia, though Victorians and Western Australians generally use gas hot water systems.<\/p>\n

Whether or not a diverter will pay for itself depends on a range of factors.\u00a0 These include a household’s hot water consumption, location, feed-in tariff, controlled load or off-peak rates, retail electricity plan, and the amount of surplus electricity produced by a home’s rooftop solar system.<\/p>\n

We have now published a SolarQuotes Diverter Comparison Table<\/a> giving the details of all the diverters we have information for.\u00a0 This article is about how they work in general and how much money they may save households in locations throughout Australia.<\/p>\n

Diverters Allow Solar Energy To Be Stored As Heat<\/h2>\n

If you know what a solar hot water diverter is, there is a good chance you’ve heard they allow your hot water system to work as a battery.<\/p>\n

This isn’t true.<\/p>\n

Batteries and hot water systems are completely different things.\u00a0 With batteries electricity goes in and electricity comes out.\u00a0 With a hot water system electricity goes in and hot water comes out.\u00a0 If you put electricity into your battery system and hot water comes out, then something has gone seriously wrong.\u00a0 And if electricity came out of my hot water system, I’d be shocked.<\/p>\n

But even though they are quite different things, both batteries and hot water systems are able to store energy.\u00a0 Batteries are able to output the same sort of energy that went into them while hot water systems are only able to store energy as heat.<\/p>\n

Diverters Use Grid Power If There Isn’t Enough Surplus Solar<\/h2>\n

If a solar system is large enough, or hot water use low enough, it is possible for a diverter to make a hot water system entirely solar powered.\u00a0 But in winter, when solar output is low and hot water consumption is high, many households will find they won’t have enough surplus solar electricity to keep their water hot during extended periods of cold and cloudy weather.\u00a0 To get around this problem diverters will allow grid electricity to boost the system when required.<\/p>\n

Diverted Surplus Solar Can Only Be Used For Electric Heating<\/h2>\n

Diverters are capable of sending even small amounts of surplus solar electricity to electric heating elements in a form they can use effectively.\u00a0 But because this power isn’t provided in the usual steady fashion it can’t be used with anything that has pumps, motors, or electronics and it’s a really bad idea to try it – just to see if I am right.<\/p>\n

As a result, they can’t be used with heat pump hot water systems<\/a>, but they can be used to give a boost to solar hot water systems.<\/p>\n

While their most common use is powering hot water system heating elements, they can also be used for home, spa, or pool heating.\u00a0 Depending on the diverter, it is possible for them to send surplus solar power to more than one heating element.<\/p>\n

If you want to see what an electric element looks like, don’t open up your hot water system, just look inside your electric jug.\u00a0 It’s that metal coil at the bottom.\u00a0 Unless yours is weird, the element will contain an alloy of nickle and chromium called nichrome<\/a> that has 100 times the resistance of copper1<\/a><\/sup>.\u00a0 The nichrome is surrounded by a ceramic insulator and the whole lot is inside a stainless steel outer layer, which is what you can see.\u00a0 An interesting fact is the ceramic insulator actually breaks when they turn it into a coil, but it still does its job.\u00a0 The nichrome conductor never comes into contact with the stainless steel exterior at least 9 times out of 10.<\/p>\n

Diverters May Have Other Features<\/h2>\n

While a diverter’s main function is to supply surplus solar electricity to electric hot water heaters, they many come with other features.\u00a0 These can include supplying normal household current<\/a> to devices that aren’t heating elements once there is enough surplus solar energy to power them.\u00a0 This is often called threshold power, as it is only provided once surplus solar reaches a set amount.<\/p>\n

Electric Hot Water Systems Have Not Been Phased Out<\/h2>\n

In 2010 it was decided to phase out<\/a> standard electric hot water systems because of the large amount of energy they use, but this has mostly been dropped.\u00a0 Probably because someone pointed out to politicians that hot water systems are still made in Australia.\u00a0 There are some building codes and incentives in place to encourage people to install something else, but it is usually still possible to install a conventional electric hot water system if that is what you want.<\/p>\n

How Hot Water Diverters Work<\/h2>\n

The amount of electricity produced by a solar system through the day varies as the sun rises and falls and because of changes in the weather, especially cloud cover.\u00a0 In addition, the amount of electricity consumed by a household can dramatically rise and fall.\u00a0 This normally results in large variations in the surplus solar electricity available.\u00a0 Often there won’t be enough to give a hot water element the power it was designed to use.<\/p>\n

The smallest hot water elements draw 1.8 kilowatts<\/a>, but most are larger and draw 2.4, 3.6, or 4.8 kilowatts.\u00a0 However, all the diverters I am aware of only work with elements that are 3.6 kilowatts or less.\u00a0 As solar systems will generally deliver significantly less power<\/a> than the maximum capacity of their solar panels, even on a clear day a 5 kilowatt solar system may be unable to give enough power for a 3.6 kilowatt element by itself and when it is overcast it will be impossible.<\/p>\n

Diverters get around this problem by taking any surplus solar power that’s available over about 100 watts and sending it to the hot water system in a form it can use. The standard way to do this is by chopping the AC power waveform into pieces.<\/p>\n

So if a solar system was producing 1.2 kilowatts of surplus electricity it could give a 3.6 kilowatt element the current it is designed to use for one-third of the time. This will result in the element heating water at one-third the rate it would if it was receiving the full 3.6 kilowatts constantly.<\/p>\n

Update 22 August: <\/strong>I unfortunately gave a wrong explanation of how diverters work and have removed the incorrect information to prevent it confusing people.\u00a0 I apologize for getting it wrong.<\/em><\/p>\n

Efficiency And Environmental Benefit<\/h2>\n

Diverters are not 100% efficient, but if they are properly designed they should be pretty close to it and lose a very small amount of surplus solar electricity.\u00a0 Because there will be a small amount of energy loss, at the moment using a diverter is slightly worse for the environment than simply sending the surplus electricity into the grid for a feed-in tariff, but the effect won’t be large and will likely change in the future as solar generation increases and we need storage to prevent clean solar energy going to waste.<\/p>\n

Controlled Tariffs And Time-Of-Use Tariffs<\/h2>\n

To determine how much money a diverter can save a household, it is necessary to look at how much grid electricity used for heating water costs.\u00a0 In Queensland, NSW, and South Australia it is common for people to use a controlled load tariff, also called an economy tariff, to power the water heater.\u00a0 This will supply electricity to the hot water system at a rate that is less than the normal tariff, but is only available for a limited period each day.\u00a0 Controlled load tariffs vary according to location and retailer plan, but prices of 17 cents or more per kilowatt-hour are now common.<\/p>\n

It is possible to use a diverter and keep a hot water system on a controlled load tariff, but this will need extra hardware that will increase the cost of installation.<\/p>\n

People who have smart meters can also\u00a0use a time-of-use tariff that provides low-cost off-peak electricity from\u00a0as little as 12 cents a kilowatt-hour in Sydney.\u00a0 Hot water systems will generally need a timer to take proper advantage of this.\u00a0 A suitable timer can cost as little as $20, but paying someone to install it can be considerably more.<\/p>\n

Hot Water Consumption<\/h2>\n

Around one-quarter of electricity consumed by Australian households goes towards heating water if they have a standard electric hot water system.<\/p>\n

I’ve looked at various figures available for hot water use in Australia and I’m afraid they just don’t add up.\u00a0 I can only conclude there are a significant number of people out there who don’t shower every day.<\/p>\n

The amount of hot water consumed by households will vary significantly depending upon how many people live there, location, time of year, personal habits and dedication to hygiene.\u00a0 Fortunately, it is very easy for people whose hot water systems are a controlled load to find out how much electricity they use to heat water.\u00a0 All they have to do is look at their electricity bills and it will be right there.<\/p>\n

If your hot water system isn’t a controlled load then working out how much electricity it uses becomes tricky.\u00a0 You could install energy monitoring equipment to find out the exact amount, or if you are like me and morally opposed to things that need effort, you could just use the following rule of thumb:<\/p>\n