What is solar panel battery storage?

If you’re considering installing solar panels at home, you’ve probably come across solar batteries, which are large lithium-ion packs that store excess electricity when there’s no sunlight. Using the same technology found in electric vehicles, these batteries let you use stored solar energy at night, charge from the grid during off-peak hours, and even provide backup power during outages.

Adding a battery can significantly improve efficiency and long-term savings, especially when combined with best solar panelsHowever, the additional investment means you need to take into account cost of solar panels And do the installation to see if the upgrade is worthwhile. Check out our guide for help estimating your return on investment Are solar panels worth it?Or check out current solar panel grants that can help defray the upfront expense.

Get a quote for solar panels on your home

Use our comparison tool to get a free quote from leading solar panel installer Throughout Britain.

How much does a solar battery cost?

Solar batteries typically cost between £2,500 and £6,000 depending on size and brand, adding around £3,000 to installation if fitted separately. For most homeowners, combining installation with new panels is the most cost-effective option.

Lloyd Greenfield, founder of Glo Green, a solar panel fitter, said: “Batteries are certainly suitable for people who typically use their energy in the evening. So if you’re a daytime consumer, without actually having a battery, this could pay off quickly.”

Here, we use our connections in the solar power market to answer key questions and do the math to determine whether batteries are a good choice for you.

How do solar batteries work?

Like a normal battery, a solar battery can be charged and discharged. In your home, they can be charged with solar power, effectively for free, or with cheap overnight electricity if your tariff allows it. An inverter then converts the battery’s lower voltage to 230v for your home ring’s mains use.

You can get a huge range of capacities, but they typically range from about 5 kilowatt hours (kwh) to about 14 kwh. You can also combine capabilities and use two or more simultaneously.

How long do solar batteries last?

These are usually guaranteed for 10 years but can last much longer.

Is solar panel battery storage worth it?

Here’s the tricky thing. It would be very useful to find out how much it costs to store energy in a battery.

Like any rechargeable battery, a solar battery also has a limited life, which largely depends on how often you can charge and discharge it.

So in theory, you could work out how many pence it costs to store a kilowatt hour (kwh) of energy and then use it.

Once you have it, you’ll be able to see if it’s worth it compared to electricity from your energy company, which will cost 27 pence under the price cap from April. For example, if you can store a kilowatt of electricity for less than 20 pence, it would be worth storing solar energy as electricity from the grid costs 7 pence more.

If you can store it for even less, it may also be worthwhile buying extremely cheap overnight electricity, such as 7.5 pence on some tariffs, as long as the storage price plus 7.5 pence is less than the grid price.

But as we are about to see, reaching this figure is not easy, and even if it does, there are other things to think about.

To make things more difficult, batteries don’t stop working after a certain number of cycles; Instead they lose more of their ability to store energy.

let’s do the math anyway

With all this in mind, let’s take a real-world example to get a figure, even if it’s not set in stone, as it will give a rough indication of whether the battery is worth it or not.

Duracell’s Dura5 storage system is guaranteed for 10 years and 10,000 cycles. If we assume we can discharge a 5.12kwh battery to 90 percent, we get 4.608kwh of usable charge per cycle. The unit can be purchased for £2,280 including VAT but not fittings.

For 10,000 cycles of 4.608kwh, a total of 46,080kwh of electricity was charged and dissipated during its guaranteed life. If we take the price and divide it by this lifetime storage figure, we get a price of five pence per stored kilowatt hour.

This is a good price, because it means stored sunlight – which is free to generate – costs only 5 pence per kilowatt hour, less than a quarter of the current grid price. If you can buy electricity cheaply overnight – some tariffs offer prices as low as 7.5 pence – then buying and storing electricity will cost only 12.5 pence per unit, significantly lower than daytime grid prices.

Cons of solar battery storage

wait! There are quite a few caveats. If the battery lasts more than 10,000 cycles, the price per use is even lower. But at the end of the battery’s life, it will hold less charge, which means the price will increase.

The price also does not include fittings, which could double the cost and bring the final figure to around 10 pence.

Again, there’s one more thing to think about – most batteries are guaranteed in years, not cycles. So, will you use enough of it in 10 years to keep the price per kWh low?

In theory, less use should make the battery last longer, but after 10 years there’s no guarantee, which may prove to be cold comfort.

In real life, like any consumer product, batteries can last longer than their warranty. It’s just that if they don’t, you’re not financially secure.

Mr Greenfield said: “We think the batteries will typically last about 15 years, maybe 20 years, depending on the quality.”

The average home uses about 2,700 kWh of energy per year, and 27,000 kWh over 10 years. This is a little less than half of the 46,080kwh in our example, with the price per stored kwh increasing if the battery dies on its 10th birthday.

If, however, you use a heat pump For central heating, your usage will be much higher, and this may make the battery viable again.

And then, of course, there is another complication. How much can you get if you sell the solar power you produce back to the grid? You can get one for as little as 15 pence from many companies, making storing it less attractive.

If you can sell energy for 15 pence and buy it back when needed for 27 pence – April’s energy cap charge – you may not think the difference is worth it.

If all this is making your head spin, and you’re looking to get a device to save money, solar batteries may not be for you.

But if you find all this math a fun exercise and you’ve found a deal where you can store inexpensive sunlight and use it at night at a lower cost than buying it from the utility company, this might be a good option.

What size solar battery do I need?

The right solar battery size depends on how much electricity your home uses and how much excess energy your solar panels generate. Most UK homes use 8–10 kWh of electricity per day, so a battery with a useful capacity of 4–10 kWh is often sufficient to store daytime energy for evening use.

If you have a larger home, an EV charger, or high night-time consumption (for example, heating or running appliances overnight), a 10-15kWh system may be more suitable. Smaller homes or those with a lower budget can opt for a 3-5kWh battery to cover major appliances and lighting.

Remember that bigger is not always better. Batteries that are too large may never be fully charged, reducing efficiency and increasing charge times. The ideal system balances capacity, cost, and daily consumption, so you store enough electricity to meet your needs without spending too much on unused storage.

How are these installed?

Solar batteries are typically wall mounted inside or outside your home. They need to be kept cool and accessible in case of an emergency.

How to find the right solar battery installer

Choosing a qualified installer is essential to ensuring that your solar battery system works safely and efficiently. look for MCS-Certified Installers (Microgeneration Certification Scheme) – This accreditation guarantees that both installation and equipment meet UK industry standards.

It’s also worth checking whether your installer is a member of the Renewable Energy Consumer Code (RECC) or the Home Insulation and Energy Systems Quality Assured Contractors Scheme (HIES). These organizations provide additional consumer protections, including dispute resolution and deposit insurance.

Before signing a contract, compare at least three quotes. Reputable installers will:

Finally, read customer reviews on Trustpilot or CheckaTrade, and ask about post-installation support. A trustworthy installer will be transparent about performance monitoring and aftercare, helping you get the most from your investment.

Should I invest in solar batteries?

If you don’t mind gambling that the battery will last longer than its guarantee, and you use a lot of power, perhaps through a heat pump or electric carOr both, and you have a large solar array to feed it, then a battery may be for you.

This is because you will get the most out of it over the guarantee period, charge and discharge it a lot, and get the cheapest price per stored unit of energy.

Glo Green’s Mr Greenfield said: “If you’re a working, busy professional, and you’re out of the house all day, and then when you leave in the evening, your consumption is high, whether that’s plugging in an EV car or running lots of power tools or lots of laundry and tumble dryers, and high consumption appliances in the evening, you would definitely be well suited for a battery.”

If you have a low-usage or small solar array, you may want to be more cautious.

Either way, you’ll need to make sure the battery is properly set up to soak up cheap sunlight during the day, and perhaps cheap grid power at night, to avoid expensive energy.