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Home batteries: are they the next big thing?

home battery

They claim to save you hundreds of pounds on your electricity bill, help you towards electricity self-sufficiency, and even let you play a part in the National Grid. Are you tempted by a home battery?

Energy storage systems – also known as batteries – store electricity in your home so you can use it when you need it. Usually this is electricity generated by a renewable system, such as solar PV or a wind turbine, but you can also store electricity from the grid.

And it looks as though batteries are moving into the mainstream.

Eon launched its solar and storage offering last month and it claims that installing a battery can help you use 30% more of the electricity you generate than with solar panels alone. Combined, it says you could make £560 a year in savings and earnings.

This week, Nissan also announced it’ll be selling home batteries – customers can choose a battery previously used in an electric car, or the pricier option of buying brand new.

And Tesla, which is more famous for its cars, sells a home battery it claims can power the average two-bedroom house for a day.

It’s early days yet for home battery storage but, with over 900,000 solar PV installations in the UK, its potential to grow is huge.

Battery storage benefits

If you have solar PV, wind or hydro turbine, it may generate most electricity when you’re not at home to use it. Unused electricity is exported to the grid and you’ll probably import electricity in the evenings.

Batteries store excess renewable electricity so you can use more of what you generate and help cut your electricity bills. They range from around 1kWh to 8kWh, which the Energy Saving Trust says is enough energy to boil your kettle between 10 and 70 times.

There’s also the potential, with time-of-use tariffs, to charge your battery from the grid when electricity is cheaper, and use up your store at times of day when electricity is more expensive.

Consumer concerns

Solar PV has the Feed-in Tariff, and heat pumps, solar thermal and biomass boilers are supported by the Renewable Heat Incentive, but there are currently no government incentives for home batteries.

So how much money you could save depends on the system you have installed and how it’s used. Many technologies are too new for there to be independent data to estimate typical savings yet.

Battery storage isn’t regulated either, although the Renewable Energy Consumer Code (RECC) was recently extended to include battery storage systems. Installers signed up to the code agree to abide by high consumer protection standards. RECC said that it has seen ‘increased interest in these products’, but also ‘a rise in complaints citing mis-selling’.

We’ve heard from Which? members with battery systems who have very different views on them. One told us about reducing their energy bill to less than £20 per month, while others have complained about systems not working as expected and installation problems. Some found the cost off-putting.

So, do you have a home battery installed? How do you use it and what do you think of it? Is there anything you wish you’d known in advance?


Sadly not enough information to take a view on this . I hope Which? will be monitoring and reporting on this growth area. However without any prices quoted and payback it is hard to say much more.

This should help readers get an overall view :

A little more investigative reporting would not have gone amiss here instead of just copying info straight from the Energy Saving Trust website.

I have found 14kWh batteries in size and 2 of these claim to be sufficient to power a 3 bedroom home for a day.

Mark says:
4 June 2018

I am looking into Battery Storage at the moment, can you advise which brand was offering 14kWh as I would be interested in looking?

We need, for example, cost and life of batteries, cost of installation and maintenance, capacity loss over time, conversion efficiency of electricity into battery storage and of battery energy into usable ac, then we can begin to assess whether they are an economic proposition, or when they might be.

Energy saving is more important than energy storage in my view – unless your house is already very efficient. It would be useful to review, factually and economically, all the energy saving measures sensible for householders – solar hot water, heat pumps, insulation, glazing, lighting. If you have solar power (wind and hydro – how many have those?) then rather than use all of it yourselves you can export more.

And if it is about saving money and oil, look to your choice of car.

An interesting concept though quite a technical one. Battery storage, a charging device and wiring into the house all need to be sorted, so the capital outlay would probably be a couple of years before it was paid for. Not all buildings are suitable for solar panels and windmills need planning permission. I would like to see research into fuel cells, so that renewable energy could be used to create things like water hydrolysis and this, in turn used to power the house. There are many schemes that use natural energy and heat re-capture. These are most useful when designed into a new building rather than added on, but there is also a danger of environmental problems when a house is turned into an insulated capsule. It’s a new and exciting science -something to be encouraged.

We’ve had solar panels for around 6 years and with a 4kwh array have found them well worth while – but only because of the FIT payments! The actual saving on our electricity use alone would take forever to repay the cost of installation. I have investigated battery back up several times but, as already stated, there is insufficient reliable and independent information available to warrant the cost of installing a battery, both from the technical side and the financial aspect. Sales people just cannot be trusted I have found.

The Introduction refers to a Which? member “reducing their energy bill to less than £20 per month“. . . . . Yes, quite.

Unless we know a lot more about the size of the household, type of property, location [Channel Islands?], lifestyle [TV, computers], whether gas or other fuels are involved, what fuel is used for cooking, heating and hot water, this is a completely meaningless statement that helps no one. Even a rough “before” cost would have been appreciated.

This comment was removed at the request of the user

This comment was removed at the request of the user

Early adopters of PV solar panels are benefiting from a favourable feed-in tariff. Each cut-back in the FIT has, understandably, reduced the appeal of solar electricity generation but it remains economically worth while because the capital cost of installation has fallen considerably. I would doubt that in ordinary situations with solar power the extra outlay for a battery installation would repay itself in a reasonable period. In a home without any renewable electricity intake I cannot see it ever being viable; we need to keep a close eye on the marketing to make sure people are not being swindled into paying for something that will do them no good.

I am sure that domestic solar power installations will continue to grow in number but the rate of expansion might now slow down. I am ever the optimist so I would expect the raw cost of electricity to start declining in real terms as the renewable content of our supplies continues to increase as the huge new off-shore wind-farms start to come on stream and the extensive commercial solar panel arrays start to ramp up their output. Indeed, there have been days lately when the UK was running on the sun and wind alone and actually receiving too much energy from renewables. This trend, if confirmed, could affect the economics of domestic installations so I think we should be cautious about battery storage systems.

I go along with Malcolm and feel that there is more mileage in energy conservation and reduction through practical measures that will help most households and improve the condition of our housing stock at the same time.

I agree with the cautious approach and doing what you can for the housing stock.

Fortunately I am about to start with a clean slate and needing to replace a 20 year old oil heater have been looking at all the options. This goes from wood-pellet to air and ground pumps by way of solar arrays. Or even another oil burner! or just electric.

The decision so far is to make one area heavily insulated and double glazed and leave the balance of the house for warmer weather days. So basically maximise one part for cold weather and being smaller than the whole is intrinsically cheaper to heat. Whether this approach works in the UK where houses are generally small is moot.

I would consider large batteries if the cost is right as I have room for PV panels aswell as panels for heating water.

However for the big problem I wish Which? would get onboard with energiesprong.uk and help drive that in the UK by publicising the considerable benefits and low costs.
” The deceptively simple idea behind the initiative has been to finance the roughly 300,000 mass-produced renovations from the estimated €6bn of savings from energy bills that they will make each year.
In the Netherlands, upfront capital comes from the WSW social bank, which has provided €6bn to underwrite government-backed 40-year loans to housing associations. These then charge tenants the same amount they had previously paid for rent and energy bills together, until the debt is repaid.
The prefabricated refurbishments come with a 40-year builders’ guarantee that covers the entire loan period, and a 5.25% return is guaranteed to participating housing associations.”
Guardian Today: the headlines, the analysis, the debate – sent direct to you

This report touches on one of the main problems for homeowners and that is getting honest and unbiased advice on what to do. The other problem is the consequent servicing.

This covers that dreaded question of how air-tight should one be. I am a fan of heat-exchanging ventilation that doe not seem to feature in this work:


In passing it knows that electric cars have substantial battery storage capacity. I recall that a year or two ago the auto industry was suggesting electric cars with the ability to provide energy back to a house if required. Sounds good doesn’t it.

It’s high time that all new buildings were built with a solar roof and oriented to make best use of the sun. Add-on solar panels are not exactly attractive. When I moved home last year I bought a house with the rear of the roof facing the right direction, so that panels would not be seen from the front. Unfortunately, not a single house nearby has solar panels. We are outside the local conservation area, but maybe there are local rules.

Since 1980 I have spent time living off-grid when on holiday, dependent on batteries overnight, and charged during the day. I first met solar panels in the early 90s when they were extremely expensive and less efficient than they are today. Solar panels are silent and once installed there is no running cost, unlike using a generator.

Knowing that you are dependent on limited battery capacity encourages conservation of electricity and this awareness has helped me become a low energy user when living in my home. If you are not using electricity for any heating other than brief use of a microwave oven and you have low energy lighting and no wasteful electrical products like plasma TVs, modest battery capacity is adequate to be independent of mains electricity for most of the year.

I’m interested in solar power and battery storage and will try to find out why none of my neighbours has solar panels.


The everchanging market always tempts one to wait, in this case to the end of the year might be worthwhile.

“Oxford PV, a spin-off from researchers at Oxford University, announced two large investments (£8.1m and £8.7m) in late 2016 from investors including Statoil Energy Ventures and Legal & General Capital. The company has also announced it is partnering with an unnamed major global solar manufacturer and intends to bring a product to market by the end of next year.”

We considered the idea – briefly – some years ago. A stack of 24v lead-acid batteries (know any old submarines being scrapped?) with an inverter strapped on and then the only bit you need an expert for is the connection to the house mains – or not, if you’re feeling brave.

We do have UIPSs in the house, powering all the computing equipment to forestall the damage incurred during power cuts (yes – they happen up here) and they’re lead-acid. But the capital outlay for the battery stack would be in the £4-500 mark, the inverter another £200 and then the cost of patching them in. We have a stream running across the bottom of the garden so I suppose we could make our own mini-hydro system.

Lead-acid batteries are the traditional way of storing electricity but there are disadvantages other than the weight. To have a reasonable working life it’s best not to discharge them more than 50% of their capacity on a regular basis and leaving them in a discharged condition for any length of time is likely to ruin them – as many caravan owners have discovered. Lithium batteries, such as those used in phones, computers, modern power tools and electric vehicles, are a much better solution and gradually becoming more affordable. Within reason, it does not really matter how they are used. Some of the inverters on sale are poorly built and unreliable, but a good inverter that is conservatively rated should last many years.

Phil says:
13 May 2017

Lithium batteries don’t like being left in a very high state of charge for any length of time. If you leave your Nissan Leaf parked for seven days with 100% charge you invalidate the battery guarantee. They don’t like deep discharge much either. All this means in practice is that a 5kwh battery is really only good for 4kwh.

Thanks Phil. It’s obviously vital to read the instructions. I knew that laptops protect their batteries from deep discharge but I was unaware that lithium batteries could be damaged if kept fully charged. I hope that does not apply to all types. As you say, the effective capacity is different from the stated capacity of the battery.

With lead-acid batteries and non-rechargeable ones, the capacity depends on the rate of discharge, and is significantly less with fast discharge. I would assume that the same applies with lithium batteries.


A fascinating look at wind power full of interesting detail. It also discusses the cheapness of the electricity meaning hydrogen as a power store.

I hope you enjoy your new home, Patrick, but I think you should ask the neighbours before storing compressed hydrogen. It could save you a bomb, or create one. 😉

Robert says:
15 May 2017

Compressed hydrogen is a terrible solution: you lose at least 30% of the energy in the electrolyser, then you have to put energy into compression, which you don’t get back. And then you lose another 35-40% in the fuel cell when you convert the hydrogen back to electricity. Furthermore, the fuel cells are very expensive. Any sort of battery system does better.

On a personal level I am sure you are correct but for mass storage of large amounts of electricity that has been generated pretty much for free you can afford to be “wasteful” as the power can be stored in bulk and has multiple uses. Driving a turbine to produce electricity in bad weather, or in adapted vehicles. – and as you are burning it in both cases the conversion back factor of 35% or so is avoided.

Note the idea that gas plants may, in some countries require the subsidy. And natural gas is much dirtier than hydrogen.

“After the dramatic cost reductions of the past few years,” explained BNEF chair Michael Liebreich, “unsubsidised wind and solar can provide the lowest cost new electrical power in an increasing number of countries, even in the developing world — sometimes by a factor of two.”
“It’s a whole new world,” Liebreich said. “Instead of having to subsidise renewables, now authorities may have to subsidise natural gas plants to help them provide grid reliability.”
How cheap are renewables now? The report lists “a hectic series of milestones for declining costs” taken from actual auctions around the world in 2016:
$60 per MWh for solar in Rajasthan, India, in January
$30 per MWh for wind in Morocco, in January
$37.70 per MWh for wind in Peru, in February
$40.50 for solar in Mexico, in March
$29.90 for solar in Dubai, in May
$60 for solar in Zambia, in June
$80 for offshore wind in the Netherlands, in July
$29.10 for solar in Chile, in August
$55 for offshore wind in Denmark, in November
Note that $29.10 per MWh is 2.91 cents per kilowatt-hour. For context, the average U.S. residential price for electricity is 12 cents per kWh.
“Solar power delivers cheapest unsubsidised electricity ever, anywhere, by any technology,” Liebreich tweeted back in August regarding the price of solar in Chile, as we reported. In that same auction, the price of a new coal power plant was nearly twice as high.


Chile must be an interesting situation. At over 2,500 miles from north to south, with the Pacific Ocean on one side and the Andes mountain range on the other, and every imaginable climate available, where do they take their solar readings?

Electricity is one of the least of our monthly expenses compared with gas, phone rentals, insurance, council tax, and other regular outlays. To spend a lot of money chiselling a marginal amount off the electricity bill doesn’t seem like the best use of our efforts. I think that, as consumers, we should be pushing as hard as possible to get the price of electricity down so that it is economical for everyone. I won’t bore readers on this occasion by repeating my mantra about the government levies on top of the energy tariffs.

One you have solar power then that makes heat pumps more affordable and then you can cut down on use of fossil fuels for heating and water heating and charging electric vehicles, though it does not help in the winter months when solar panels produce little power.

I don’t think the government’s initiatives have been right, but I do support balanced use of the various forms of renewable energy.

I’ve always wondered why more isn’t done to utilise the heat produced by a conservatory. The average conservatory becomes extremely hot with only a small amount of sunshine. Instead of using that heat, we all shade it or open doors and windows. A simple heat pump could use it to heat a large amount of water – the main cost for any home.

We have two heat pumps and I can vouch for their astonishing efficiency.

I’ve never understood the obsession with conservatories. They are generally too hot in summer, too cold in winter, and why do we need light in all directions and then stick in blinds to cut it down? Because they are cheaper than a conventional extension, I suspect, but much less comfortable. At the very least, use a lightweight insulated tiled roof, or one with water pipes to provide warm water for the house (in addition to those on the main roof perhaps).

I have never been a fan of conservatories but having inherited one when I moved house I can see some advantages. Early in the morning it can be much warmer than the house, so no need for heating. The warm air is wafted into the house, so no need for heating when the conservatory becomes too warm. With the doors to the garden open I can sit and watch and listen to the birds.

With plenty of light coming in through the windows, I wonder if there is scope for solar panels on conservatories, and then add a home battery.

Alfa posted this link in another Conversation, showing that a solar roof does not need to look like rather unsightly solar panels added to an existing roof:

Just the job for new homes and other buildings, together with batteries of course.

Desmond Brown says:
9 May 2017

I have used a 3.5KW PV system for over 4 years. It just happened to fit on my garage roof facing a few degrees W of South. On a clear summer day we generate 25-30 KWh. The company suggested we would average 3000KWh per year and we have, very closely, so far. I had checked my consumption over the previous several years and it ran at 4000KWh per year.
Several observations have emerged. With the grants, it is a good financial return on the capital. As a green solution, it’s not as good as I hoped. We have retired and are very active away from home especially in summer. Hence we are not using the power we generate.The best we have managed is less than 30% over the years and that is actively running the laundry on sunny days etc. The next observation is that our power consumption has dropped about 50%, we are out a lot and the lights have been replaced with low energy bulbs and will probably go to LED on the next change. What to suggest? If you have young children and a big daily demand for electricity, you will use a bigger proportion of it than us, probably diverting the surplus to an immersion heater. If finance is tight, have a good look at low energy bulbs and devices. Switch stuff off.
It is tempting to think that with a storage system we could be independent but winters are long and dark, some winter days we make 200-300W, not enough to keep a battery charged. So I doubt if an expensive storage system is worthwhile.
At sea I have added an 80W PV system and controller to my bank of 12v batteries (semi-deep cycle) so far it has powered instruments and a fridge without having to resort to shore power or the engine but that’s a different world. If you have been reading, best wishes

Thanks Desmond. Practical application and analysis is much appreciated.

I cannot see that the government would want to create any incentive regarding these storage batteries since to charge a battery would be pushing less energy back into the national grid. It may reduce what one would take from the national grid but would energy companies have an interest in reducing ones bills, and as such would the government assist in this when the whole point of utility privatization was to make the rich ever richer and the poor ever poorer. (Give the peasants a few hundred quid in shares and then tell them then eat cake!)

I am approached about 3 or 4 times a year by these commission making battery sales persons. It seems they have obtained a national list by surreptitious means as to who has solar panels. They phone with all sorts of stories such as they have taken over the company who installed ones panels to sending details of the massive savings. Just lead them on and state that lithium batteries do not have marvelous safety record etc. and then hear the next chapter of their sales pitch. It is music to ones hears providing ones is not taken in, and there is nothing worth watching on ones TV.

It seems as if when one sales racket comes to an end such as double glazing another starts up such as solar panels but now they cannot sell quite many of them because of the reduction in FIT they have moved towards batteries instead.

There is another racket in the making however after these batteries. It is that your Inverter (Converts the low voltage DC from ones panels to mains voltage AC) are not that efficient and/or they can individually convert each of your panels 24 volt DC to mains thus reducing the effects of shadowing and spreads in solar panel output efficiency level etc. All very nice but if only the figures they create had a basis on scientific facts and/or represented and thus match your individual installation.

As for the green issues. Has anyone counted the total energy consumed to make these batteries, the petrol to get the salespersons and their cars & vans to your address, the energy to heat the buildings and premises they work from etc?

Dick Fletcher says:
13 May 2017

Patrick Taylors link to the BRE site is most useful. Thank you.
It is a pity that Which? did not include this at the start. The Which? report is superficial and not helpful in sofaras it provide links to other authorities on the subject.

I think these systems are interesting, but savings will depend on your usage. Cutting usage by using LED lighting and turning off standby, and appliances not in use will probably give a better return more cheaply at present. Most people could save more money by better home insulation . Our electricity bills are just £300 a year, and at a guess we could only save maybe £75 a year using a battery system.

If we had an electric car and used that battery as well as our solar panels, then it would be a more integrated fit, not needing a separate battery.

So I am not opposed to battery systems, but first of all reduce your use, insulate, get efficient appliances. You stand to save more as well as reducing your effect on climate change.