Charging Your EV From The Grid Is Cheaper & Greener Than Charging From A Home Battery

Charging electric car from a solar battery

Solar & EV owners: don’t stress about charging your car directly from the grid when the sun isn’t shining.

The first thing I’ll do in this article is point out it’s difficult to fit caveats into a headline.  The second thing I’ll do now I’m writing the article and have the space to explain is state there are exceptions to the two main points I am about to make, which are:

  1. It doesn’t make economic sense to charge an electric car with a home battery.
  2. Charging an electric car with a grid-connected solar-battery is worse for the environment than simply charging it from the grid.

I will cover some exceptions later in the article, but not now.  Maybe in paragraph 46.  The first thing I am going to do is lay down some ground rules on technology and how far into the future I’m going.

The Next 5 Years

I’m only looking at the relatively near future, which means I’m going to assume home batteries and electric cars will work much the way they do now without any radical changes in technology.

I’ll also assume Australia’s electricity generation will only be around 50% renewable by 2030.  I’m hoping it will be considerably higher, but as I’ve had three failed marriages I have to consider the possibility my optimism levels are slightly above average.

I’m confident my two statements made above will hold true for the next 5 years, but after that it’s possible they will no longer apply.  So in the year 2025, if man is still alive, if woman can survive, they may find… the situation has changed and it makes sense to charge an electric car with a home battery.  But I doubt it.

Stored Solar Energy Isn’t “Free”

I’m afraid there are some people who are living in a dream world.

They are under the impression it is cost-effective to charge an electric car in the evening with a home battery that’s been charged with solar power during the day.

I wish I could join them in this dream world, but I’m afraid I cannot.  This is because, sooner or later, I know that giant carrot in a top hat will show up and start chasing me again.  (He’s the reason I sometimes write these articles at 3:00 a.m. in the morning.)

But another problem — one that doesn’t involve a giant, snappily dressed carrot with muscular legs — is this costs more than simply charging the car from the grid throughout Australia.  This is because:

  1. Whenever energy from rooftop solar panels is used to charge a car, either directly or from a home battery, the household loses out on the solar feed-in tariff they would have received if the electricity had instead been fed directly into the grid.
  2. There are always losses when charging and discharging batteries.  Using a home battery to charge an electric car’s battery pack will, more or less, double the losses.
  3. Battery systems cost a lot of money and this needs to be accounted for.

In addition to these points there are retail electricity plans available now that can — at least potentially — lower the cost of charging an electric car.  These are likely to become more common in the future.

Foregone Solar Feed-In Tariff

It may seem obvious solar electricity used to charge a car can’t also receive a solar feed-in tariff.  It’s like what my father told me when I wanted to marry two women, “You can’t have your Kate and Edith as well.”  But people who don’t know the ins and outs of solar power and energy storage can’t be blamed for not knowing this.  There are battery salespeople who deliberately ignore it in their spiels about battery savings and then there are those who don’t even understand it’s necessary.  This means they’re advising people without knowing the very basics of how battery payback works.  That’s pretty scary.

No, wait.  Not scary… shitty.  Shitty is the word I was looking for.

The amount of solar feed-in tariff you get depends on your location and electricity plan.  In Perth it’s fixed at only 7.1 cents per kilowatt-hour.1  In Sydney Origin Energy is currently offering a plan with a 21 cent feed-in tariff.  This is more than what they now offer in South Australia.

The lower your feed-in tariff the less it will cost to charge a battery with solar, but the cost will be increased by…

Battery Losses

I recently looked at a report from the Canberra Battery Test Centre and estimated, on average, home batteries only provide around 84% of the energy put into them.  If I bump that figure up to 85%, around 1.2 kilowatt-hours will still need to be put into a battery to get 1 kilowatt-hour out.  This means if you have a 7.1 cent feed-in tariff in Western Australia to use one kilowatt-hour of stored electricity will require 8.6 cents of solar electricity, while with a 16 cent feed-in tariff 19.2 cents worth will be needed.

There are also losses when charging an EV’s battery, but if you are going to use an electric car these are pretty much unavoidable, so I’ll ignore them.2

The graph below shows:

  •  The standard tariff3 in each capital.
  • The solar feed-in tariff.  In capitals with retailer choice I simply used the Origin Energy plan with the highest feed-in tariff offered to normal households.4  For Perth and Darwin I used their fixed feed-in tariffs, while for Hobart I used First Energy’s, which was the best of the two available.5  This is also how I obtained the figures for the standard tariff.
  • The amount of solar feed-in tariff foregone to for each kilowatt-hour of stored energy used.

Solar feed-in and electricity tariffs

Battery System Cost

Like most things in life, the more a battery is used the more wear and tear it suffers.  (One of these days my sarcasm is going to be completely worn out.)  There is only a limited amount of energy a battery system can provide during its lifetime, so its cost per stored kilowatt-hour provided needs to be accounted for.  If we consider a Tesla Powerwall 2 — the most famous of home battery systems — and use the following assumptions:

  • Its total installed cost is $16,000
  • It provides an average of 10 kilowatt-hours of stored energy per day.  This is an optimistic figure for any home that’s remotely close normal.6
  • It lasts for 13 years and provides a total of 47,500 kilowatt-hours7

This results in the cost of the battery system per kilowatt-hour of stored energy being 33.7 cents.  As that’s more than most Australians pay for grid electricity it’s clearly not going to pay for itself.  Including the cost of foregone solar feed-in tariff just makes it worse.

To be thorough this figure should also include the cost of capital, but I’m not going to worry about it.  Just keep it in the back of your mind the real cost will be a little worse.

It is possible the cost of batteries will soon come down or maybe it’s possible to just get a really good deal now, so I’m going to assume the cost of a battery is only going to come to 30 cents per kilowatt-hour in most of Australia and only 17.4 cents in South Australia due to that state’s hefty battery subsidy.

Total Cost Of Home Battery For EV Charging

If we take the cost of the battery system per kilowatt-hour and add the cost of the foregone feed-in tariff and compare it to the cost of a standard tariff in each capital we get the following:

Standard electricity tariffs and cost of energy storage

As you can see, even using an optimistic example, it costs more to charge a car with solar power from a battery than to simply use grid power on a standard tariff in every capital.  The only place it comes close to paying for itself is Adelaide and that’s only thanks to the substantial battery subsidy available there.

Darwin is the worst capital for charging an electric car from a home battery thanks to having the nation’s highest feed-in tariff, while Canberra is the second worse thanks to having Australia’s lowest electricity prices.

While things already look awful, a standard tariff is not the only way to pay for grid electricity to charge a car and other options can make the comparison considerably worse.

Low Cost Grid Charging

Depending on your location there are a number of ways already available to charge a car with grid electricity at a lower cost than a standard tariff.  These include:

  1. Charging with off peak power on a time-of-use tariff.  Solar homes are usually better off with a standard tariff, but if you are charging an electric car at night it may make one worthwhile.
  2. Make your EV charger a controlled load.  This will provide lower cost electricity but you will only be able to use your charger for a limited amount of time per day.
  3. Use an electricity plan where you are pay wholesale prices for grid electricity.  Amber Electric is an example.

Other methods of charging an electric car at reduced cost are likely to become available in the future.  If an EV charger is smart enough it will enable charging when electricity prices are low, zero, or even negative — meaning at times the household will be paid for charging their battery and potentially for consuming electricity in the home.  This graph from Thursday last week shows several periods of negative electricity prices in South Australia on a windy day:

Electricity price and demand - spot price

Prices fell to negative 50 cents per kilowatt-hour.  Being able to take advantage of events like this is clearly useful and in two years time it will become possible to pay for electricity in 5 minute blocks rather than having the price averaged over 30 minutes.  This graph shows 5 minute prices on that day:

Electricity price and demand - dispatch price

There were many, brief, 5 minute periods when the wholesale price of electricity dropped down to negative $1 per kilowatt-hour.  EV chargers and home batteries that can make use of these 5 minute settlement periods will have a considerable advantage.  On the other hand, the more storage capacity there is the less often electricity prices will go negative.  We are still in the early days of allowing households to take advantage of swings in wholesale electricity prices and it remains to be seen how much they will help home batteries pay for themselves.

Home Batteries Are Bad For The Environment

You may not care how much it costs to charge an electric car with a home battery and just want to do it to help the environment.  That’s a great attitude, but not a great idea.  This is because using a home battery is bad for the environment as it increases emissions.

As I explain here, each kilowatt-hour of solar electricity sent into the grid for a feed-in tariff will reduce fossil fuel generation by around one kilowatt-hour.  But because of charging and discharging losses a kilowatt-hour of solar electricity stored in a battery will only reduce fossil fuel generation by around 0.85 kilowatt-hours.  This makes it better for the environment to send surplus solar electricity into the grid than storing it in a battery.  As renewable generation increases and coal power stations are shut down this should change, but unfortunately it’s likely to take Australia more than 5 years to get to that point.

Paragraph 46 — Some Exceptions, Caveats, & Provisos

In this section I’ll cover some situations where my contention that charging an electric car with a battery doesn’t make economic or environmental sense may not apply.

  • First, just to be clear, I’ll state that driving an electric car will result in less greenhouse gas emissions than driving a comparable standard internal combustion engine car.  At the moment a hybrid can easily beat an electric car on emissions, but with enough renewable generation electric cars will beat hybrids.
  • If your home or business is export limited and your battery is storing clean solar energy that otherwise would go to waste then the battery can be an environmental plus and reduce emissions.  This also improves its economics.
  • Virtual Power Plants have the potential greatly improve the economics of home storage, but it remains to be seen how much benefit they will provide households and how long they will take to become an easily available option.  They are unlikely to make charging an EV with a home battery pay for itself soon.
  • The current low cost of battery cells compared to what they were just a few years ago indicates home battery storage has the potential to fall a long way in cost.  If prices fall faster than predicted, charging cars with home batteries could make economic sense sooner than I expect.
  • If you already have a home battery then it’s a sunk cost.  If you are not planning to replace it after the end of its lifespan its cost isn’t a consideration in how you use it.  If you are intending to replace it then you should take the expected cost of its replacement into account.  For example, if you think home batteries will be much cheaper in 5 years time you may not mind using your battery in a way that will cause it to wear out rapidly.  You may decide to do the same if you are planning to move and have a home battery you can’t take with you.

To Sum Up…

Unless there are special circumstances, charging an electric car with a home battery won’t  pay for itself anytime soon and it’s also likely to remain an environmental negative for a considerable time.  However, while it seems unlikely to me, if technology changes fast enough it may make sense within 5 years.

So feel free to go out and buy that electric car without worrying about having enough home-battery storage to charge it every night.


  1. Or nothing if your inverter is larger than 5 kilowatts.  WA is basically the evil fairy godmother of solar electricity.
  2. You can reduce electric car losses by using the most efficient charging method.  For example, charging from a normal power point is less efficient than using a dedicated charger.
  3. A standard tariff charges a flat amount for each kilowatt-hour of grid electricity used.  Its mirror universe twin is a time-of-use tariff where the charge per kilowatt-hour depends on the time of day.
  4. Origin’s highest feed-in tariff isn’t available to the vast majority of homes.  I wish they’d stop making it appear that it is.  I’d have thought they’d be in trouble with the ACCC by now.
  5. First Energy, which is Tasmania’s second electricity retailer.  Didn’t anyone involved realise that wasn’t the best name to go with?
  6. Because of battery degradation, normal household variation in consumption, and low solar output in winter and on cloudy days; most households will average much less than 10 kilowatt-hours of stored electricity use per day.
  7. We don’t currently know how long the average Powerwall 2 can be expected to live beyond the 10 year warranty it has if charged with rooftop solar, but because battery cells degrade with use and an average of 10 kilowatt-hours a day would be higher than average use, I would not expect it to last for a long time beyond its warranty.
About Ronald Brakels

Joining SolarQuotes in 2015, Ronald has a knack for reading those tediously long documents put out by solar manufacturers and translating their contents into something consumers might find interesting. Master of heavily researched deep-dive blog posts, his relentless consumer advocacy has ruffled more than a few manufacturer's feathers over the years. Read Ronald's full bio.


  1. Mark Byrne says

    Can someone please clarify which networks allow EV chargers to be on controlled load circuits?

    • Ronald Brakels says

      That’s a good question. I know in Queensland Ergon allows electric car chargers to be on economy tariffs 31 and 33 provided the charger is hard wired so it can only be used when the economy tariff is available. I don’t know what the rules are off the top of my head for the rest of Australia. I know that according to some DNSP’s terms of use you are not permitted to connect the latest Nissan Leaf to the grid because it has the ability to provide electricity to the grid. (But I doubt that will be enforced provided people are only taking electricity from the grid.)

    • Powershop has an offpeak 9c inc gst off peak rate from 12-7am for anyone with a registered ev, benifit is also the rest of the house get the rate too, so you can schedule appliances or even top up your home battery for cheap

  2. Ian Thompson says

    Great article again Ronald…

    Thank you for presenting the facts of physics so clearly to us.

    • It’s another great article.

      Lets enjoy the peace before some tiresome twit tells us we are all idiots for even thinking about buying a fancy new electric car when anyone with half a brain could build their own billy-cart for free!

      • Ian Thompson says

        Hear, hear…

        Test-drove a Tesla model S a while back – very impressed – but will have to wait a while until my existing car needs replacement, maybe then go for a Model 3 instead (in WA a good range is mandatory).

      • ….. and my guess would be that YOU couldn’t build a billy-cart…
        And might one add that a billy-cart is an infinitely more cost-efficient and environmentally-friendly mode of transport than even a battery-powered Dinky Toy.
        It’s accepted that it probably wouldn’t impress the neighbours nearly as a much as a multi-thousand-dollar Gee-Whiz-Mobile.
        …. and as for the much-vaunted ROI on the capital outlay….. the mind boggles as much as loss of capital gains! (Though one supposes you’d buy it on the Never-Never, which would normally cost you 250% of the advertised price-tag.
        …Can anyone remind me of the olde saying about a fool and his money?

      • ps…….electric cars were tried and found hopelessly inadequate 100+ years ago, and discarded as a useful option..
        I remember Grandma Duck’s one was forever creating problems.

  3. graham franklin-browne says

    Hi Ronald,

    We have just upgraded our solar from 3.2 Kwh to 10 Kwh, turned off our gas heating, and installed a battery with a link to the Reposit power guys in Canberra who manage our export limited system online.

    We have gone with a high tech panel heating solution which is definitely not cheap to run compared with RCAC but we dont like blown air heating although it is taking us some time to learn to run efficiently.

    Our daily driver is a Nissan Leaf, and because we work part time it gets charged a couple of times per week – some of that is during the day.

    We “shop” for green-sourced power through Powershop but we are still drawing big chunks of energy from the grid. According to your analysis we seem to be doing a lot of things wrong, but our saving grace might be that although we cannot control who puts energy into the grid, we can choose who we pay to take it out. Maybe.

    Anyway, we are here for the long haul and I have calculated an ROI on our current setup at around 11 years.

    One thing we have learnt through our journey is that generating your own power come with a responsibilty to manage your daily life in regard to the weather and your energy requirements (I have never been more aware of the weather since starting this transition).

    Keep up the good work and we look forward to hopefully hearing better news about batteries in the future.

    Graham and Finola

  4. Old Gregg says

    You don’t need to to fit caveats into your headlines. All you need to do is pop a “*” (an asterisk) at the end of the headline, just like everyone else does.

  5. Len Norris says

    “At the moment a hybrid MIGHT beat SOME electric cars on emissions”

    There fixed that for you. Saying hybrids easily beat EV emissions is just wrong….You need caveats for your caveats. Emissions are a state by state proposition so if charging 100% from the grid then the comparison changes. Charging with rooftop solar will further alter those calculations.

    • Ian Thompson says

      Interesting Len

      Top Gear ran a competition for fuel economy around their racetrack, between a Prius Hybrid, and a high-end, very powerful BMW M3. The “deal” was for the Prius to be driven as hard as possible for a given number of circuits, and the M3 to basically follow it around at the same speed (obviously having a very easy time of it).
      The result – the much more powerful M3 was about 5-10% more fuel efficient.
      The conclusion – it’s not so much what you drive, but how you drive, that impacts fuel economy. Fuel consumption relates directly to CO2 emissions.

      Here in WA, we could fully charge a 62 kWhr Tesla Model 3 “Standard Range Plus” from fully flat using excess Solar generation, for less than $5 of forgone FiT (only 7.135 c/kWhr here, 92 % losses one way). For an advertised range of 460 km, and I’d say virtually zero emissions (ignoring the manufacturing and delivery processes). A little over 1 cent per kilometre travelled, if you assume the capital cost of the solar system is being recovered by other means. Compare this with my near-equivalent I.C. car, which burns about 6.5 litres of fuel/100 km costing about 10 cents per km – producing much CO2 to do so. The EV also has much lower maintenance costs.
      However – I think you’d have to also factor in the replacement cost of the EV battery with these figures, to get a meaningful cost comparison. As far as emissions go, I’d say it was no contest – although I guess you could still argue that the foregone FiT represents a lost opportunity cost for reducing emissions elsewhere. But, I wouldn’t want to use a battery in between, for all the costs and emissions penalties Ron has presented.

  6. I live in Perth and have a 6.5 kWh solar with Powerwall setup. Our lovely Synergy (the only provider in Perth) refuses to pay for my exported power as they claim my 3 phase power makes it impossible to tell if I’m exporting solar or already imported grid power. They don’t care that the battery isn’t configured to store grid power at all.

    So to not hand over power to them for free I need to use as much of my solar generation as possible at home. Therefore I believe charging an EV from solar and battery would make perfect sense.

    • Ian Thompson says

      Wow Kim – that is an interesting issue. I, too, live in Perth, have 6.24 kW nominal panel capacity driving a 3-phase 5kW inverter, but no batteries.
      In my case, I may be importing on one phase (nett), and exporting on another – but the Smart meter simply takes the total nett power into account – whether it’s a nett import, or export.

      Why would they think you would want to import power costing 28.2 c/kWhr to charge a battery, lose 15% of that in battery return trip, and sell it back to them at 85% of 7.135 c/kWhr? And even if you did, surely that is only a benefit to them? Unless they’re concerned about “time shifting” around a Time of Day type tariff – but even then?

      I’d write to my local minister, and ask for a clear explanation of their reasons from the State Energy Minister.

  7. Great article but not sure on some of your assumptions here. I had a Tesla Powerwall installed for 12,500 full cost onto my existing 5 year old 5kw solar through Origin at 24 months intrest free without any government incentives which are now readily available in most states dropping the price well below 10k for the 13.5kw battery.

    The Tesla Powerwall allows time shifting in the App for those on smart meters to maximize not just solar but off peak power usage topped put from the grid without the need for reposit style or vpp extra cost installs.

    Smart meters can also be installed for free in most areas to take advantage of time shifting (i got mine through powershop) in Brisbane free.

  8. Daniel Debreceny says

    At the current time, off-peak is predominately supplied by coal.
    It may be ideological, but it’s important to some people, and decreased demand will drive the wholesale price of power during off-peak lower.

    Export limitations and adding battery to your existing hybrid system allowing you to add extra panels, ie; solaredge SEx000 (non HD-wave series), How much does this affect the calculation?

    A short reminder that in July, feed-in tariffs were generally slashed (along with retailer profitability) due to revision of the standing offer plans, and they slashed the “market offer” plans.

    In future, I see the price of the FIT being slashed again, and we’ll need to re-visit the evaluation.

    So currently, we’re awaiting:
    1) Price drops on batteries (stubbornly staying high due to increased demand)
    2) Car Chargers supporting feed-in (to make your low FIT + battery per kWh costs less than peak tariffs.

  9. Ian Thompson says

    Hi Ron

    I see you have picked up on Synergy’s (WA) recent 1.75% tariff hike – to 28.8 c/kWhr after tax – at least my system will now pay for itself just that little more quickly (sorry – looking for an upside!).

    They also hiked our supply charge by 1.75% – but I did notice they left the FiT at 7.135 c/kWh! Annually, the supply charge is by far and away our biggest nett cost component.

  10. Graeme Martin says

    Very thought-provoking. We have 6.5 kW panels and 6 kWh batteries, in WA. My plan was to plug the future EV car into the house when the house batteries were full (usually the early afternoon). The cost would be the forgone (pathetic) feedin tariff.

  11. Steven Schulte says


  12. So (as Ronald reminds us) if home batteries are currently uneconomic how do electric cars stack up ? How long before you are back in the black driving one (not counting one you can claim a business tax deduction – just a home user) ?

    Would like to see a detailed running cost comparison to the average home fuel powered vehicle. If anyone has see a layman’s comparison already done then would appreciate a link.

  13. Richard Courtenay says

    Just don’t move house too soon or you may still be paying for a system you don’t own.
    We are %70 off grid. We could not afford to buy the size battery bank in lithium but have 12 x 530 ah agm and panels which power our house 24/7 except for electric oven, welding and occasionall dryer. Hot water is off peak $45 per quater so solar h/w not viable.

    • Oh come on now Richard! You KNOW that that’s Billy-Cart-Age technology!
      What WILL the know-all neighbours say?

  14. Des Scahill says

    It’s one thing to buy a Triple A Grade rated battery from the absolute best manufacturer of such battery in the entire world (whoever that may be).

    Quite another to have it installed correctly, and maintained properly once you’ve got it.

    According to this 9 News item published just a few hours ago at:

    9 News quotes from a draft NSW Budget document as follows:

    “High installation rate with an unprepared workforce, poor training, poor auditing scheme leads to injury/death/reputational damage,” the document, seen by AAP, said.
    There is also a significant risk of medium- to low-income families being “enticed” into loans they may not be able to pay back. ”

    The ingredients are all there to be seen, for mammoth problems ahead. Just to illustrate:

    – Australia’s leading energy retailer can’t even organize the installation of new electricity meters without stuffing it up.

    – There’s manufacturers around who can’t even make electric scooters for kids that won’t catch fire (see

    – Audi has just recalled its new EV due to ‘fire risk’ (see One would think they would have learned from Tesla’s experience (Tesla can proudly make claim to being first in such events)

    – State Governments (such as Queensland) that change the rules every12 months or so on just about everything connected with solar installations.

    Seems naive to me to expect that anything different from the above will happen in the rather infant EV and home battery market, given the state of affairs that exists at the moment with what’s already around.

    So, waiting at least 5 years as Ron suggests seems very good advice to me. At least that way you might well avoid the possibility of ending up with the solar equivalent of a ‘My Little Gumnuts Wet Bag’ ( see: )

    Hopefully, in 5 years time, we’ll have sorted out the problems that already exist (including grid related issues), rather than adding yet another layer of even more complex ones on top of things.

  15. Ian Thompson says

    Hi Richard

    I’ve been looking how we could get “off grid” for some time now – but for us it’s just way too uneconomic.

    Can I ask, how much did your 76kWhr of AGM sey you back? Or, did you mean 530 Whr, not Ah?

    What do you mean “70%” off-grid? Do you still pay the daily supply charge, to allow you to run the oven, welder, etc., when necessary?

  16. Hi,

    If I was to spend the money and buy an EV, I would install a Stand Alone system solar/battery/inverter/EV charger. That would enable charging whenever I wanted, and not effect my FiT. Possibly make use of some of the excess in the house/garage.


  17. Lawrence Coomber says


    Yes good analysis.

    And for a domestic Standalone Solution (PV – Battery – Inverter) – 15 KW+ PV is the sweet spot (plus 20 KW 1/3 Phase Standalone Inverter). A comparably sized Battery Bank can vary in both chemistry and capacity a bit, and Permanent System Autonomy Smart Load Control Logic is essential.

    Lawrence Coomber

  18. “It doesn’t make economic sense to charge an electric car with a home battery.

    Charging an electric car with a grid-connected solar-battery is worse for the environment than simply charging it from the grid.”

    Is there any reason you omitted the third and most obvious answer?? —>
    (Google): Charging Electric Cars with Solar Power. SolarEdge released a new solar inverter that charges EVs for a more efficient energy transfer. Owning an electric car that is charged by a solar power system is an excellent way to ensure your transportation is both cost-efficient and emissions-free.

  19. Greg Greet says

    Well of course it aint necessarily so. If you are not connected to the grid & a connection costs $50-100k! I still aim to use solar (daytime) charging though.

  20. Howdy Ronald
    I’m interested to hear what you think about the “greenest” way to charge an electric car.

    We just bought a Kona EV which has a pretty large battery, so we don’t need to charge it often (once or twice a week). We’ve also got 6 kW of solar which exports much more than we need to charge the car.

    So we’ve got a couple of choices-
    a) only charge the car during the day when we’re exporting solar; or
    b) only charge the car at night and purchase 100% accredited greenpower

    I figure that option (b) is probably the greenest (although the most expensive): let’s say I export 100 kWh/week, and my car needs 40 kWh/week to charge it, I get:
    option a) The grid is supplied with 60 kWh/week of renewable energy from my solar, vs

    option b) The grid is supplied with 100 kWh/week of my solar, plus a further 40 kW of accredited greenpower, i.e. 140 kWh/week.
    That means an extra 80 kWh/week of non-renewable that I have displaced from the grid.

    But maybe it’s not as simple as that, because
    option (a): I’m adding energy when there’s already a glut of solar power available that can’t be used or stored, which makes it harder for solar farms to make money
    option (b): I’m consuming power at night when renewable energy is in shorter supply, hence increasing the demand for non-renewables and improving their profitability.

    What do you think?

    • ah – just realised that I phrased that last part badly; what I meant was:
      But maybe it’s not as simple as that, because for option (b) I’m adding extra energy to the grid when there’s already a glut of solar power available that can’t be used or stored, which makes it harder for solar farms to make money
      And I’m consuming more power at night when renewable energy is in shorter supply, hence propping up the demand for non-renewables and increasing their profitability.

    • Ronald Brakels says

      Hi Richard

      Of the 2 options (b) will result in the least emissions. While you are correct this will very slightly push down electricity prices during the day and discourage the building of new solar farms, this effect may be countered by low daytime electricity prices during the day resulting in more coal generators leaving the market, so I wouldn’t worry too much about that side of things. But if you want to help take strain off the grid and help reduce grid over voltage issues, then charge your car in the middle of the day.

      I’ll mention that low off-peak rates and or controlled loads will become available in the middle of the day in the future. For example, I’m in Queensland at the moment and here it is normal for the off peak hot water systems to be turned on during the day. So you could end up charging your car at a cheap rate in the daytime.

  21. Lawrence Coomber says

    Richard consider installing a Specific Circuits Off Grid [Standalone] System for your EV and add some other circuits [possibly pool filter or HWS etc] with duty cycles that suit daytime PV Power sources only.

    Of course if needed, these circuits [or some of them] can be switched back to Grid supply via COS if required at any time.

    This is a common commercial factory scenario where the business in mainly a day time operation and therefore efficiently suits an Off Grid Solution; but the same logic applies to domestic premises also.

    Importantly you can install an Off Grid [Standalone] System at your premises as well as having an On Grid System already in place and the Off Grid System qualifies for STC’s at the PV nameplate value.

    Lawrence Coomber

  22. Hi Ronald and Lawrence

    Thanks for the information and advice


  23. Marten - NL says

    Hi Ronald,
    Maybe it’s better not to write your articles at 03:oo in the morning.. I live on the otherstide of planet earth in the Netherlands. I’m really suprised about your conclusions of what is cheaper in sence of energy. A wrong way of thinking is my opinion!
    Ofcourse it is cheaper for the individual person/citizen to not buy batteries/wall-homepower material. Ofcourse it is cheaper to recieve money from your energy provider after fixing pv’s on your rooftop. But that is not the issue here in 2020. What we need to do is think different, we need to lower the consuming from OUR AC-grid, because in 10 years everybody is driving in EV cars, think ahead and invest in local power. Maybe not individual wise, but in houseblocks we need to fix a second grid with DC power, solar>battery>EV charging and bidirectional converting, ALL DC powered! In the Netherlands were we now allready start to feel the need to change the AC-grid because of over consumption of EV-battery chargers and also feeding the grid with solarpower panels. Our cables and powerstations are getting overloaded by all these new local ‘powerplants’, not too mention the datacenters..
    Here is an article from our tecnical universities.
    Think ahead! There are new batteries coming soon which will change the world. Great to read about these off-grid solutions down under!
    Best, Marten.

    • Trevor Jones says

      You are obviously much smarten than Ronald and also understand more about electricity. I don’t think he even understands the difference between AC and DC. I know this article is a few years old but he still seems to be suffering from the same misconceptions. I am including a link for him to try and learn something . Whilst we have people like Ronald that keep sprouting rubbish because a lack of understanding we will continue to hold back development.

      All evs are increasing in the maximum voltage of their batteries and the voltages are similar to those of hv DC home storage batteries. If people like Ronald and his boss Finn Peacock could understand this and help to push for direct DC charging of EVs at home whether from the inverter/charger or the DC battery we could elimate some of the waste of power being converted from DC to AC, going out onto the grid and then coming back from the grid converting from AC to DC to sore in the car battery. DUH as Homer says “wake up Ronald”

  24. Lawrence Coomber says

    Marten both you and Ron are on a road to nowhere in this discussion.

    But I acknowledge it is a very difficult road to step away from, as it seems like abandoning what initially [for some] looked like the global march to eternal utopia; but may turn out the march of the lemmings instead.

    It never was; and can now never be a global reality. How come?

    Well in a word it was an ’emotional’ subject from the start and continually force fed on ever expanding ’emotional’ rhetoric. Say stuff enough times it becomes mainstream practice and immune from serious debate moving forward. And that’s how it happened.

    Ron has always given us all some clues on this subject moving forward by introducing the science of commercial viability when discussing batteries and TCO [total cost of ownership] of energy technologies etc, but has been noticeably shy in moving his thoughts beyond batteries and applying similar logic to other forms of miniscule scale and usefulness renewable technologies such as solar PV and Wind.

    I say miniscule purposefully because that is what we have globally after 15 years of near mass hysteria over solar PV, wind, batteries and most recently EV’s and also pumped hydro. And at what cost? Well its astronomical and for no net tangible benefit to the global power needs moving forward, which call for at least 40 times the existing annual global power generation, to power the new era developing world to a universal modern industrialised standard by 2075.

    Important to note here but never mentioned in hysterical technology forums and commentary is the global population of around 7 billion now will double by 2060. Go factor that into your technology for the times thinking.

    Miniscule in anything – and particularly power technology just doesn’t cut it moving forward gentlemen.

    We have all just sat back and been totally mesmerized by what will be looked back on in time, as hysterical nonsense chasing miniscule and self indulgent boutique technology sugar hits, and as a consequence abandoned technological break-through fertile-ground.

    Opportunities have been surrendered and global science largely diverted into miniscule technologies. We will have lost effectively 25 years of scientific endeavour chasing rainbows looking back that cannot be reclaimed.

    What a waste of global scientific opportunities.

    So let’s now return to your EV stuff Marten, I have had my say.

    Lawrence Coomber

    • Geoff Miell says

      Lawrence Coomber,
      You state:
      “Important to note here but never mentioned in hysterical technology forums and commentary is the global population of around 7 billion now will double by 2060.”

      What makes you think “the global population … will double by 2060”? Do you have any references that you base your statement on, Lawrence?

      Where do you think the adequate food and water supplies will come from to sustain a global population, as you suggest, that’s “double”, or 14 billion, “by 2060”, Lawrence? Where will the adequate, long-term sustainable, affordable and suitable forms of energy supplies come from to enable adequate food and water production and supply chains for a population of that size? I’d suggest if water and food supplies are inadequate and/or unaffordable, then populations simply will not grow.

      On Feb 14, David Spratt made a presentation at the National Climate Emergency Summit 2020 outlining that a 1.5°C temperature rise (above pre-industrial age) is likely by 2030.
      See the slide titled “1.5°C likely to be reached by 2030”:

      Increasing global temperature rise will reduce global food production yields.

      “Most regions in the world see a significant drop in food production and increasing numbers of extreme weather events, including heat waves, floods and storms. Food production is inadequate to feed the global population and food prices skyrocket, as a consequence of a one-fifth decline in crop yields, a decline in the nutrition content of food crops, a catastrophic decline in insect populations, desertification, monsoon failure and chronic water shortages, and conditions too hot for human habitation in significant food-growing regions.”
      See the scenario outlined in “EXISTENTIAL CLIMATE-RELATED SECURITY RISK: A scenario approach” on page 9 found at:

      Will a glut of oil and gas now quickly flip to global oil shortages when the COVID-19 crisis ends?

      “The problem we have since the 2008 oil price shock is that oil prices must be both affordable to consumers AND high enough for the oil industry to survive. The Corona virus is hitting an economy and financial system which have a precondition of accumulated debt incurred during the high oil price period and while the era of low cost oil has ended long ago.”

  25. Lawrence Coomber says

    Geoff small-scope energy science technology thinkers at the global scale are part of the problem not the solution, and they certainly don’t get any traction at all in serious forward thinking research discussions.

    I understand that global climate change is largely fuelled by greenhouse gas emissions from fossil fuel energy generation, and gasoline powered engines. I also understand that over half of the world’s population are energy starved and as such are denied opportunities to aspire to the modern standard of living enjoyed by those of us fortunate enough to exist in an energy abundant society. I know this energy starved world well, having worked as a power/systems engineer throughout many nations [and still do] for over 50 years now.

    It is axiomatic that the energy deprived must do what it takes to redress this imbalance. The math around this premise are astonishing. The current world’s total generation output by all forms may need to increase by a factor of 40 over the next 50 years to begin to seriously start to redress this energy imbalance! Let’s not forget, the current global population of 7 billion will double by 2060, irrespective of whatever science brings forth in the interim; or worse, doesn’t bring forth.

    NID + P = AACSE (National Infrastructure Development + Prosperity = Abundant Available Clean Safe Energy)

    Energy commentators and readers might benefit from pondering a bit on the simple term “the new age global energy generation imperative”; it has a book worth of meaning in its few words. The “new age global energy generation imperative” demands an enduring [ad infinitum] energy science solution that:-

    1. Must be an energy dense technology able to deliver abundant, safe, clean and low-cost energy; and at the apex of the energy science pyramid;
    2. Reduce energy generation global greenhouse gas emissions to insignificant levels permanently;
    3. Be scalable and easily deployed cost effectively to power new age energy intensive industries and businesses;
    4. Be available through modular design to cost effectively benefit all people throughout the world.

    The key takeaway term is: “abundant, safe, clean and low-cost energy”. A core technology that gets that right – will precipitate the beginning of the development of all other critical core new age energy intensive sciences, technologies and businesses.

    Nuclear fuelled energy generation technology has distinct advantages over the “minuscule and boutique” clean energy generation alternatives such as solar PV and wind power that we currently see being promoted everywhere in near hysterical fashion.

    So why isn’t there a critically needed and equally noisy global discussion going on about “new age clean safe nuclear energy generation” science? Or maybe that discussion is already maturing in the policy boardrooms that really matter, rather than the overly hyped mainstream energy media forums.

    Revisit the new age energy equation above and ponder what underpins National Infrastructure Development: NID + P = AACSE (think high speed rail; think new age energy intensive industries including the replacement of traditional agriculture with new age molecular level food manufacturing technologies; reflect on new energy intensive water management science technologies based on the abundance everywhere of sea water; the list goes on and on, but only if we perfect enduring ad-infinitum Nation Building Energy Source Technologies ASAP.

    We live in very exciting times as technologists, and our endeavours and outcomes today must be useful and sustainable and fit for purpose for a highly populated world to aspire to a meaningful and modern “for the times” standard of living for all people.

    This is the scientific goal to aspire to, and nothing less is acceptable.

    Lawrence Coomber

    • Geoff Miell says

      Lawrence Coomber,
      You haven’t answered my previous question and reiterate your statement:
      “Let’s not forget, the current global population of 7 billion will double by 2060, irrespective of whatever science brings forth in the interim; or worse, doesn’t bring forth.”

      I repeat: What makes you think “the global population … will double by 2060”? It seems to me you are avoiding the question – perhaps it’s too inconvenient for you?

      Evidence I see indicates unless humanity rapidly reduces human-induced GHG emissions within the 2020s then escalating dangerous climate change will likely reduce food production yields – “one-fifth decline in crop yields” by 2050. Inadequate global food and water supplies means population growth will stall and decline. So, I don’t see how the human population can grow much further, let alone double by 2060, if food production declines. I think it’s a pretty simple principle: Inadequate food/water – you soon die.

      You also state:
      “Nuclear fuelled energy generation technology has distinct advantages over the “minuscule and boutique” clean energy generation alternatives such as solar PV and wind power that we currently see being promoted everywhere in near hysterical fashion.”

      What “distinct advantages” would that be, Lawrence? I see some critical DISADVANTAGES for nuclear-fission-based energy technologies:
      1. Far too expensive;
      2. Far too long to build/deploy – inadequate to mitigate escalating dangerous climate change;
      3. A finite fuel supply – not long-term sustainable;
      4. A toxic waste legacy that will long outlast any energy benefits gained.
      See my Submission (#096) at:

      Nothing happens without energy. Unaffordable energy means life becomes unaffordable.

      I have no doubt we do live in interesting times – the evidence I see indicates this is the critical decade for humanity to finally get on the right path or fail dismally for current and any future generations. There’s no reset and there’s no planet B.

  26. tony bamford says

    i have just read the pros and cons of charging Ev,s this way and that, but no mention of the cost of the saving the cost of fuel offset and reduction of pollution.isn’t this the whole point? .

  27. I do not agree. If my Tesla has supplemental power that I donot need for the home, I am happy with putting it in a car. You are wrong with 7.1 cents FIT in Perth. It is a tually 2.8 cents and after 3 pm 9.8 cents. There is not much generation after 3 pm.
    So nothing I want to go in the grid because they sell it to my neighbour for 27 cents !

    Battery use for the car makes perfect sense if it is charged by solar and you do not otherwise need it. Charging from the grid means you drive your car on coal. It defeats the purpose of an EV completely.

  28. Hi,

    Is it technically feasible/logical/economic to have an EV and charge it from solar during the day, and then use it as a battery plugged in to the inverter during the evening. Assume you’d have to have a hybrid inverter to enable the grid to be connected and isolated if the EV was supplying power to the house.

    I live in Melbourne, am considering a Solar system and an EV in the near future.


    • Ronald Brakels says

      Technically, it can be done. In practice, it can’t at the moment — at least not by people who aren’t part of a trial such as one that is being run in the ACT. A few electric cars can provide a limited amount of power to run appliances, so that’s one way to do it. But I wouldn’t recommend it for normal use. One problems is EV battery packs aren’t necessarily as durable as batteries used in stationary home storage and so the wear and tear from ordinary day to day use may end up costing more than is saved on electricity bills. But there is a lot of potential for EVs to supply power to the grid during critical peaks when the wholesale price of electricity can go over $15 per kilowatt-hour. If an EV supplied 50 kilowatt-hours to the grid over a year at times when the prices was $10+ per kilowatt-hour, that relatively small amount of energy would be worth $500+.

      Hopefully V2G will become an option for almost everyone who buys a new EV in the future, but at the moment we are mostly reliant on developments overseas. We are something of an EV backwater compared to say, Norway.

Speak Your Mind

Please keep the SolarQuotes blog constructive and useful with these 5 rules:

1. Real names are preferred - you should be happy to put your name to your comments.
2. Put down your weapons.
3. Assume positive intention.
4. If you are in the solar industry - try to get to the truth, not the sale.
5. Please stay on topic.

Get The SolarQuotes Weekly Newsletter