A Guide to Solar Batteries 2019

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Solar batteries allow you to store excess electricity generated by your solar panels to use as and when you need it.

A solar battery costs around £1,500 to £6,000, depending on how much electricity it's able to store.

Solar batteries can be installed at the same time as solar panels, or can be retrofitted to solar panels which have already been installed.

solar battery house

What's in this guide to solar batteries?

Jump straight to a section by clicking on the links.

What is a solar battery?

A solar battery is an energy storage system that homeowners can connect to their solar panels. It is usually made from lead acid or lithium-ion, and can store up the electricity that your solar panels generate while you’re out during the day. Lithium-ion batteries are the best on the market, offering fast charging and high capacity.

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The best solar batteries in 2019

The best solar batteries on the market in 2019 are: the Enphase AC Battery, the Nissan xStorage, the Moixa Smart Battery, the SolaX Battery System, the LG Chem Resu, the Tesla Powerwall, and the Samsung SDI. We’ve popped them all into a nice table, including information about capacity, warranty, and weight.

Battery model






Enphase AC Battery
10 years
Wall mounted (indoor only)
Nissan xStorage
5-10 years
Wall mounted
Moixa Smart Battery
10 years
Wall mounted
SolaX Battery System
10 years
Wall mounted (indoor only)
LG Chem Resu
10 years
Standing or wall mounted
Tesla Powerwall
10 years
Standing or wall mounted
Samsung SDI
5 years

Information updated in April 2019.

Enphase AC Battery

California-based Enphase knows all about sunny weather. Its AC Battery is an ultra-lightweight solar power storage option, weighing just a feathery 23kg. With 1.2kWh of capacity, this battery isn’t going to take you off the grid, but it will still provide you with serious solar energy gains. The AC Battery also has a 100% depth of discharge, which means you can use all 1.2kWh of its capacity before recharging it (some solar batteries aren’t as generous).

Nissan xStorage

Japanese car-maker Nissan has branched into solar power storage. In collaboration with American energy management company Eaton, it has created the xStorage solar battery, half of which are recycled car batteries from electric Nissan LEAF cars. The xStorage battery comes in at a hefty 135kg, but it’s a high-performing, reliable model, offering up to 7.5kWh of capacity.

Moixa Smart Battery

The Moixa Smart Battery is an intelligent bit of kit, capable of charging day and night. Once the sun goes down, the Smart Battery will start to charge from the grid (when rates are cheaper), ensuring that it’s almost always topped up. Moixa also has a scheme called GridShare, which gives Smart Battery users a free extended warranty (and three £50 payments in the first three years) in exchange for any unused electricity. Moixa then trades this electricity with the National Grid, in support of a low-carbon future.

SolaX Battery

The SolaX Battery is all about convenience, designed to be small, slim, and compact. It also comes with a very easy ‘plug and play’ installation process, which is a big time-saver (and money-saver) when it comes to installing the battery.

LG Chem Resu

LG is a big name in the home electronics and solar industries, and its Chem Resu solar battery is suitably high-performing. It’s available in no less than five different capacities to suit your needs, ranging from 2.9 to 9.3kWh. The battery itself is sleek, shiny, and metallic, meaning you can store your solar electricity and be stylish at the same time.

Tesla Powerwall

The impressively named ‘Powerwall’ is Tesla’s answer to solar power storage. Quite fabulously, the Powerwall is a futuristic-looking white box that operates almost entirely without noise. It can be installed quickly, requires little to no maintenance, and operates with liquid thermal control. What’s more, if you get hooked on solar power storage, you can stack up to 10 Tesla Powerwalls on top of each other. With 13.5kWh of capacity, the Powerwall is substantially the most powerful solar battery on the market.

Samsung SDI

The Samsung SDI ‘All-in One’ neatly packs three functions into one clever box; lithium-ion battery, PV inverter, and battery inverter. If you’re low on space, the SDI’s compactness is really handy. The battery comes with 3.6kWh of capacity, a 90% depth of discharge, and a smart lick of blue paint.

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How much does a solar battery cost?

The cost of a solar battery generally ranges from £2,000 to £6,000, depending on variables such as the battery’s capacity, material, lifespan, and installation process. Obviously, the more electricity a solar battery can store, the more it’s likely to cost.

A Which? survey found that 25% of members paid under £3,000 for their solar battery storage system, while 41% of members paid between £4,000 and £7,000.

You’ll normally find better deals if you buy a solar battery and a solar panel system at the same time, but that doesn’t mean you can’t find a good value solar battery as a solo purchase.

Are they a good investment?

Solar batteries can seriously increase the money-saving potential of your solar panels. For example, according to E.ON, with a 9.6kWh solar battery (and 12 x 315W panels) in central England, you could use up to 30% more of the energy your solar panels generate, and decrease your annual energy bill by up to £560.

So long as you buy a reliable solar battery (or batteries) with a decent lifespan (like the models listed above), your solar-plus-storage system will do a lot more with the sunshine than lone solar panels.

Now is a great time to switch to solar; on 1st October 2019, VAT on solar panels and solar batteries will increase from 5% to 20%, so it's wise to get everything sorted before autumn.

To receive free, tailored quotes for solar panels and solar batteries, simply answer the question below, and fill in the quick form – our professional installers will get right back to you.

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What happens to all the solar power that doesn’t get used?

Solar panels are genius pieces of technology, but you’re not getting the best out of them until you’ve united them with a solar battery. Solar batteries store up the electricity that your solar panels generate throughout the day, so it’s there for you to use when you get home.

Solar companies all over the world have realised the importance of “solar-plus-storage” systems, and every man and his dog is recommending that homeowners get their hands on one.

On this page, we’ll tell you everything you need to know about solar battery storage, including the best solar batteries on the market in 2019, and their typical costs.

To find out how much a new solar battery will cost you, simply fill in the form at the top of this page, and our qualified installers will be in touch.

Retrofitting a solar battery to an existing solar PV system

If you already own solar panels at home, that’s not a problem; you can easily retrofit a solar battery to an existing solar PV system.

When the solar battery is installed, it must be either AC-coupled or DC-coupled, and this depends on the type of inverter that your solar panels are using.

If your PV system has a microinverter, then the solar battery will have to be AC-coupled. This is the cheaper of the two options (as you won’t need to replace the inverter), and the installation process is fairly quick. However, this solution does lead to additional energy loss over time, because it involves converting the solar-generated electricity twice.

On the other hand, if you don’t have a microinverter, then you’ll need to replace your existing inverter with one that can work with your solar battery. This is more expensive up front (your whole system will need to be rewired), but it only involves converting the solar-generated electricity once, so there is less energy loss in the long term.

To find out how much it will cost you to retrofit a solar battery to your solar PV system, simply fill in this quick form, and our professional installers will be in touch. They can help you work out exactly what size battery you need and whether it needs to be AC-coupled or DC-coupled.

How do they work?

When solar panels operate on their own, the majority of their efforts sadly go to waste. This is because solar energy can be used only as and when it is available.

93% of homeowners we surveyed think that solar batteries are a good investment*

*Based on a survey we conducted in January 2018 of 310 UK homeowners with a solar battery storage system.

The peak time for solar power generation is in the middle of the day, when the sun is at its highest point – but that’s also when you’re not at home. You’re unable to use it, and the electricity just goes into the grid. Then, once you’re back home in the evening, your panels have clocked off for the day; the sun’s down, and you have to pay for the power you use.

Fortunately, teamwork makes the dream work. Enter: the solar battery. Chuck one of these bad boys into the mix, and you’ll be getting way more out of your solar panels. All the unused electricity that’s produced throughout the day goes into your solar battery for safekeeping, ready for you to use whenever you need it. When there’s little or no daylight (or there’s a power cut), you can turn to your solar battery for assistance.

Most solar batteries aren’t designed to make you entirely independent from the National Grid, but they can make a huge difference to your energy bills – not to mention your carbon footprint. However, some models – such as Tesla’s 13.5 kWh Powerwall 2.0 – are big enough to keep you off-grid entirely, if you so wish.

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Pros and cons of a solar battery


More solar power. With a solar battery in place, you’ll use more of the electricity that your solar panels create. This means you’ll be using less of the National Grid’s power supply, and reducing your carbon footprint even further

Energy bill savings. Increased solar power usage also means lower energy bills - Increased solar power usage also means lower energy bills - just take a look at the example from E.ON in the ‘Are they a good investment?’ section above.

Backup power supply. When a power cut strikes, your smug little box of energy will suddenly become very useful. Some batteries are programmed to switch off when there’s a power cut (due to risk of electrocution), but certain models (such as the Tesla Powerwall 2.0) are built to operate independently of whatever nonsense the grid gets up to.

Increased independence. Energy companies are always hiking up their prices and getting more money out of their customers. Buy a solar battery, and that’s one big step towards off-grid self-sufficiency.


Expensive. With most solar batteries costing somewhere between £2,000 and £6,000, it’s not a cheap purchase – but for most people, the benefits outweigh the initial expense.

Demands on your space. Some high-capacity solar batteries are about the size of a small kitchen fridge, so be ready to give over some room for one of these things – especially if the model can only be located indoors.

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How big is a solar battery?

There’s no one-size-fits-all answer. Solar battery dimensions vary depending on their capacity; a 2kWh battery is about the size of a microwave and is capable of being mounted on a wall, while most fridge-sized 13kWh batteries need to be stood on the floor.

What size solar battery is needed to power a house?

You can calculate the amount of battery storage you need based on your energy usage, which is measured in kilowatt hours (kWh) over a certain period of time, e.g. kWh per day. According to Smarter Business, the average UK household uses between 8.5 and 10 kWh per day, or 3,100 kWh per year.

Generally speaking, a three-bedroom house will need a 3-4 kilowatt peak (kWp) solar panel system, which consists of around 12-16 panels and produces approximately 2,500 kWh of electricity per year. To go with this, a three-bedroom house would need a solar battery with around 3-6kWh of capacity. However, if you’re wanting to go completely off-grid, you’d need at least a 10kWh-capacity battery.

As a rule, it’s much better to have multiple batteries in your solar storage system and use around 40-50% of their capacity before recharging them. If you just have one battery and repeatedly use 100% of its capacity, you’ll degrade its power and efficiency much more quickly. You can learn more about a solar battery’s ‘depth of discharge’ further down the page.

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How much electricity can a solar battery hold?

The ‘capacity’ of a solar battery refers to how much electricity it can hold, measured in kilowatt hours (kWh). A ‘kilowatt hour’ is equivalent to one kilowatt of power sustained for one hour.

Most solar batteries on the market today generally have a capacity of 3-7kWh, although you can also find smaller and larger models to suit your needs.

You should also consider a solar battery’s ‘power rating’, which is how much electricity a battery can deliver at any one time (measured in kilowatts, or kW). If a solar battery has a high capacity but a low power rating, it will be able to hold a lot of electricity, but you won’t be able to power many things at once.

Fortunately, most models of solar battery are stackable, so if one isn't enough, you can just pile more on top. For example, up to 10 Tesla Powerwalls can be stacked on top of each other before things get too dangerous/silly.

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How long do they last?

A solar battery lives a trying life of repeated charging and draining ‘cycles’, which gradually wears it away - similar to the way your mobile phone battery gets steadily worse.

As shown in the table near the top of the page, the typical warranty of a solar battery is 10 years. This doesn’t mean that a battery will stop working after 10 years, but it will usually start to operate at a reduced level (e.g. around 70% of its original capacity). After about 15 years, you will probably need to replace the solar battery.

As your solar battery goes through cycles, it will slowly experience a decrease in its ‘depth of discharge’ (DoD), which refers to how much of a battery’s capacity is actually useable. For example, if you own a 10kWh-capacity battery with an 85% DoD, you should only use a maximum of 8.5kWh at any one time. If you repeatedly use 100% of the battery’s energy, it will wear away the battery much more quickly.

Fortunately, you yourself can have an impact; proper maintenance, along with protecting your battery from significantly low or high temperatures, will keep it ticking along nicely. What’s more, technological advances are continually increasing the lifespan and performance of solar batteries, so things are only going to get better.

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What type of solar battery should I buy?

Once you’ve decided to buy a solar battery, you need to decide on its chemical composition and electricity current. It’s wise to speak to multiple professional installers about this before you make a decision.

Lead acid or lithium-ion?

Lead acid batteries come in two varieties: flooded or sealed. The typical lifespan of a flooded lead acid battery is a bit longer than a sealed lead acid battery (5-7 years vs 3-5 years), but it also requires more maintenance. If you’re looking for the cheapest type of solar energy storage system, the flooded lead acid battery is best for you.

Lithium-ion batteries are the most expensive type of solar battery, but they’re very compact (about half the size of a lead acid battery), and have a typical lifespan of more than 10 years. Furthermore, they have a higher efficiency, a faster charging ability, and much more capacity. You’ll definitely get value for money from one of these.

AC or DC?

While the Aussie rock band went for a bit of both, you have to choose one or the other. If you’re installing a solar battery at the same time as solar panels, it’s best to opt for a DC (direct current) battery, which connects directly to the panels and doesn’t require an additional inverter.

If, on the other hand, you already have solar panels, you’ll need an AC (alternating current) battery. These are much easier to retrofit to an existing system, as it is connected via the electricity meter, but it also requires an additional inverter.

You should always seek professional help when choosing and installing a solar battery storage system. Make sure your installer is signed up to the Renewable Energy Consumer Code (RECC) as this ensures that they’re signed up to a high standard of conduct, and covers you should you need to make a complaint or claim.

Good to know: when installing a solar battery, you’ll need to tell your local Distribution Network Operator (DNO), and you might also be required to inform your local council.

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Finding a professional installer

The next step is finding a solar battery that’s right for you. To start collecting quotes from qualified installers, simply answer the question below, fill in the form, and our suppliers will get back to you. You’ll be stockpiling solar energy in no time.

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