energy technology

What we learned from getting a battery installed

If you’re a regular reader, you’ll know that I’ve been working to improve the efficiency of my house. I had an interim target to reach an A rating for efficiency by 2020, on the way to zero carbon by 2025. The latest step has been to install a domestic storage battery. This will allow us to make more use of our solar power. We would have done it at the same time as the solar panels, but we couldn’t afford it all at once. We’re having to do things step by step.

There are a couple of good reasons for doing it now however. One is that the economics of solar has shifted. We put as many solar panels as we could fit on the roof, and over the last couple of years we have used less than a quarter of the energy they generate. The rest gets exported and we get paid for that. We still draw half our power from the grid, mainly overnight and in the winter. But in the first couple of years of generation we made more money back from the power we sold than we paid in electricity bills, offsetting our costs and putting us slightly in profit. That’s no longer the case.

Energy prices have risen, but the price paid to domestic solar producers hasn’t kept pace. Today we receive 10.48p per kilowatt for selling our exported surplus. We pay 38.5p per kilowatt for importing from the grid (it was 17p in 2019). I don’t know who’s pocketing the difference, but I do know that it makes much more sense to use the power than to export it.

With cheaper batteries and higher energy prices, the logic of batteries has shifted. The other reason to do it now is that Luton Council ran a community buying scheme through the Solar Together platform. I might write a separate post about the benefits of a scheme like this later. For now, it saved us around 15% on the price of a battery, and gave us more substantial guarantees than we might have got independently – in exchange for trusting the organisation’s choice of battery brand and supplier. We ordered a 6.5kw battery through the scheme, which cost £5,500, and it was installed within five weeks.

At that size, the house won’t need to draw on grid electricity for about eight months of the year. It will meet our overnight energy needs and top up during the day right into late autumn. We’ll still depend on the grid for occasional car charges when we need a quick turnaround, which currently happens maybe once a month.

Until recently the conventional wisdom has been that storage batteries don’t necessarily break even. Higher energy prices change that, but it’s still a long term pay-off. For us, it also lays some groundwork for the next stage of home improvement, which is to fit a heat pump. I’ve had the quotes in and I won’t be able to afford it until I sell another book or two. When the heat pump arrives, we’ll switch off the gas into the property and we’ll be all electric. Our electricity usage will rise considerably, as it has already with the electric car, and the battery will support that and keep bills manageable on an all-electric and zero carbon household.

A few observations on getting a battery: first, it’s not particularly easy to get good information. It’s actually quite difficult to even get a quote at the moment, as demand is so high. I couldn’t get the guys who did my solar to give me a price as a comparison. They never got back to me, and that’s something I’ve heard from others. That means it’s hard to know what value for money is on batteries. There’s not much information online, price estimates are very vague, and it’s hard to know what brands to look out for.

Give it a couple more years, and you’ll be able to get a battery through your utility company, or you can call British Gas and they’ll do it. There will be more and bigger installers with a more consistent offer, and it will get easier.

One thing that annoyed me is that batteries are charged full rate VAT and my invoice included £919 paid to the government. I may be wrong about this, so correct me if I’ve overlooked a good reason for taxing batteries, but this seems a little obtuse. More homes with grid-connected batteries eases peak-time demand. It makes it easier to manage the grid, integrate renewable energy and provide baseload. That seems like something we should encourage, and lower VAT rates are an obvious way to do that. What’s particularly annoying is that batteries are zero VAT if you install them at the same time as your solar, but full VAT if you add them later. That’s a strange distinction that I expect will be fixed at some point, too late for us.

As for the installation itself, it took two guys about three hours to do. The power was off in the house for about ten minutes. There was no mess, and drilling was fairly minimal. It would take longer if you were putting the battery in a loft or a garage, but ours is under the stairs and an easy run to the meter cabinet for the installers. If you’ve got somewhere out of the way to put a battery, that’s better. They’re not exactly elegant things, and in our small house there’s little choice of location. I might need to box it in somehow if we ever come to sell the house.

We’ll have a better sense of how the battery is working out after a full year of use. For now, I’m happy to answer any questions about it if you’ve been considering it.

What I learned from getting an EV charge point

Yesterday the electrician was round to fit a domestic charge point to the front of the house. We can now charge the car without having to run a cable through an open window, which is just in time for the first sub-zero temperatures of the season. For the benefit of anyone else considering one, here…

How we insulated under our floors

Regular readers will know about my plan to get our house to an A rating by 2020, and net zero by 2025. I missed the 2020 deadline due to the government mis-handling the Green Homes Grant, but this week the underfloor insulation went in. I won’t be commissioning a new Energy Performance Certificate to confirm…

What I learned from having external insulation fitted

One of my current projects is to try and get our 1920s terraced house an A rating for energy efficiency by the end of 2020. Some of my plans haven’t worked – underfloor insulation was thwarted by a complicated and only partially accessible crawlspace. Solar heat storage came to nothing because we don’t have the…


  1. Interesting blog Jeremy, thank you. As it’s unfamiliar territory for me at the moment I’d love to hear how you go about controlling power movements between solar, battery and grid. I assume you try to make best use of what you generate and off-peak grid power, but which app do you use, and what infrastructure gives the best visibility of what’s happening?

    I’m currently waiting on planning permission for solar and associated batteries so I’m really looking forward to joining you on this journey!

    1. Good questions. Most of it is automated at the meter box. The solar panels serve the house first, meeting any demand. Any surplus to demand then goes into the battery until it’s full. Once it’s full, which isn’t going to happen much at this time of year, it will go to the grid. That all happens without any intervention from me.

      One exception is the car charger. It’s a Zappi, which is designed to integrate with solar panels. I can fast charge when necessary, but I can also set it to trickle-charge the car off surplus solar.

      I was using the SolarEdge system, which has a very good and clear app. The Zappi charger is controlled through the Myenergi app. And the battery runs on something called ShinePhone, which has the most features but is overcomplicated and not 100% reliable. I have three apps because I fitted the solar, the charger and the battery at different times and different suppliers. Ideally they’d all talk to each other, and Myenergi can do that.

      Some people choose to charge the battery up at night on an Economy 7 tariff. That’s not something we’ve looked into at this stage.

  2. Really interesting points raised for changing the system

    The lack of information and complex variety of factors also makes me feel too ignorant to make a decision.

    As a result it seems I renewed and upgraded my batteries capacity and now…. have too much capacity for my panels. Not particularily impressed as it cost 11.000. I live 100 percent solar.

    The concept of a dedicated firm that manages the potential financial subsidies and can get bulk order discounts sounds ideal.
    In Spain because I do not have a electricity bill to reduce I am not eligible for any subsidies!
    So many gaps that the early birds seem to suffer from.
    Thank you for making me critically consider the system. VAT should be 0


    1. Yes, it is hard to make a good decision when information is unreliable, and early adopters can get stung. Off-grid users being ineligible for grants is another slightly crazy loophole!

  3. This is something I really, really need to get sorted but the number of companies and different options I find too intimidating. What’s the best way to make sure I get the right company with the best deals (or government incentives) for my area (Cumbria)? What process should I go through? Also, whatever route I take, it’s going to have to be something I can pay for in instalments – even £5000 for a battery is not something we have in savings!

    1. It’s a tricky one, and we were lucky that the Solar Together scheme ran locally and made it easy for us. You could ask your council to take part – well worth it, and people across the region would benefit with you. There may be options through your energy supplier too. Some have battery schemes, some don’t. Those that don’t will probably release one some time soon. I’ve noticed that Ecotricity have one ‘coming soon’.

      All reputable suppliers should be registered for any government support schemes, where they exist. They’re different in every region, and I don’t know much about Cumbria. One starting point though might be to get a quote from a company with a good network of suppliers, and then see who gets in touch. Myenergi, for example. Ideally there would be a good local solar company that can do different battery brands and offer impartial advice, though they’re very busy right now!

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