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A Beginner’s Guide to Solar Batteries 2022

A solar battery saves the typical house £200 per year

It also cuts your carbon footprint by 0.94 tonnes

The average solar battery costs £4,500

Solar panels make wonderful use of the Earth’s natural resources – but you have to use the power they produce straight away, or it will be wasted.

A typical household ends up wasting around half of this money-saving, completely renewable energy.

By purchasing a solar battery, you can cut almost a tonne of greenhouse gases from your carbon footprint, and save £200 per year on your energy bills.

This storage device can also help you become more energy independent, which could mean the days of stress and worry at the thought of price spikes and power cuts are over.

Here’s everything you need to do if you’re considering adding a solar battery to your system.

To find out how much a new solar-plus-storage will cost you, simply fill in this free form, and our qualified installers will be in touch.

solar battery on a wall

What is a solar battery?

A solar battery is a device that allows you to store the excess electricity your solar panels generate, so you can use or sell this energy at a later time.

Unless you or the people you live with are at home and using electricity every minute of every day, you’ll have solar power that goes unused.

Typically, you’ll lose 50% of the electricity produced by your solar panels this way – but not when you have a solar battery.

The two main types of battery are the inferior lead acid model and the superior lithium-ion battery, which offers faster charging and a higher capacity.

How does a solar battery work?

A solar battery works as an overflow storage unit.

When sunlight hits solar panels, they turn this natural resource into direct current (DC) electricity, before converting it into alternating current (AC) electricity that powers your home.

And when your home is fully powered, any excess solar energy will be rerouted to charge your battery, in much the same way you charge your phone.

After the sun goes down and you can’t actively draw power from your panels, it’ll be time for your solar battery to shine, providing you with all the energy it’s gathered.

This will happen automatically, with your panels and battery seamlessly passing the baton between them, so you won’t need to worry about monitoring the system.

The sun's time in the sky and the times you use energy at home don't line up perfectly, and a battery solves this problem.

How much does a solar battery cost?

A solar battery typically costs £4,500, though the exact amount depends on its size, its brand, and the materials it’s made from.

Batteries also require little to no maintenance, so your initial outlay will probably be the last time you have to spend money on them.

You’ll usually pay 10% to 20% more for a solar battery that can take you completely off-grid, which typically works out to around £5,000.

For more information on how much you can expect to pay, read our guide to solar battery costs.

And for the best solar batteries available this year, take a look at our comparison article here.

How long does a solar battery last?

Solar batteries often come with a 10-year warranty, and usually last for 15 years – though they may run at a slightly reduced capacity for the last five years.

They have to perform repetitive, daily charging and draining cycles, and just like your phone’s battery, this eventually wears them out.

If you buy a top-quality model – such as the best solar battery, which we’ve identified below as the Powervault 3 – the chances are higher that it’ll last beyond its 10-year warranty.

What is ‘Depth of Discharge?’

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 10 kWh-capacity battery with an 85% DoD, you should only use a maximum of 8.5 kWh 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. Carrying out 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, which means they’ll only improve.

Is a solar battery worth it?

A solar battery will save you £200 per year at current prices, but it’s still not worth it – just yet.

Let’s start at the beginning. If you don’t have a solar battery, you’ll typically end up not using around 50% of the power your solar panels produce.

You can sell this extra energy back to the National Grid, through the Smart Export Guarantee (SEG), but you’ll only receive a maximum of 5.57p per kWh.

Electricity currently costs more than three times that, at 18.9p per kWh, so you’ll save much more money if you simply store your excess energy in your solar battery for later.

The average three-bedroom house with solar panels will generate 1,492 kWh of spare energy per year.

To see if solar batteries are worth it in the UK, you can read our guide here.

This will save you £364, made up of £282 you won’t have to pay the National Grid, and £82 you can get by selling your excess power through the SEG.

However, if you could use this extra energy instead of selling it, you’d save £564 – which is £200 more – and that’s where solar batteries excel.

Solar panels usually last 25 years, meaning you’ll probably need to buy two sets of batteries over their lifetime, costing a sizable £9,000.

That will dwarf your £200 annual saving on your energy bills, making the investment a poor one at the moment – but this will change.

Electricity prices have risen by 19% in the past three years, and show no signs of slowing down, while the cost of solar batteries is going down all the time.

This means that in the near future, saving all the electricity you generate will be extremely profitable.

Pros and cons of a solar battery

It allows you to save £564 per yearIt costs £4,500 on average
You’ll reduce your carbon footprint by an extra 15%You’ll have to set some space aside for it
You can be more energy independent, so energy price hikes will affect you less
You’ll have your own energy supply when a power cut happens

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. This is 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.

What’s the best solar battery on the market?

The Powervault 3 is the best solar battery on the market at the moment.

The 4 kWh model is just £3,229, comes with a 10-year warranty, and is the smallest top-tier battery available right now – so it won’t take up much space.

You can also monitor how your battery is doing online. All in all, British company Powervault has hit it out of the park with this machine.

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.


The next step is to find a solar-plus-storage network that suits your home perfectly – especially considering 65% of people told our latest National Home Energy Survey that they'd buy a house with solar panels.

We're entering a new, green era, and you can reap all the rewards.

Just complete this short form, and you can get free quotes from qualified installers. You’ll be taking advantage of everything solar batteries have to offer in no time.

josh jackman
Josh Jackman Senior Writer

Josh has written about eco-friendly home improvements and climate change for the past three years. His work has featured on the front page of the Financial Times; he’s been interviewed by BBC Radio; and he was the resident expert in BT’s smart home tech initiative.

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