guide

A guide to battery storage for solar PV

03 November 2021 | Celia Topping

If you have solar panels, or are thinking about installing them, then you should also consider battery storage

In this guide, we’ll reveal the pros and cons of solar battery storage and how much it could save you. Plus, how to know whether battery storage is the right choice for your home. 

What is solar panel battery storage?

Quite simply, it’s storage for the electricity you generate with your solar panels. So you can store the energy you generate from the sun in the day, and use it when you may need it most, like at night. 

How does it work?

Without going into too much unnecessary detail: the inverter for your PV system  converts the electricity you can’t use (DC electricity) into electricity you can use in your home (AC electricity). Then the battery stores it. So if you generate excess power, it doesn't go to waste. 

Basically, your panels charge the battery, so you can use it later, when you need it. \

What type of battery is best for solar?

There are 3 types of batteries that are most commonly used for solar battery storage: lead-acid, saltwater, and Lithium-ion.

Of these 3, Lithium-ion batteries will last the longest and need the least amount of maintenance. They’re also non-hazardous, but they do cost more than the other 2 types. 

What are the benefits of solar battery systems? 

If you already have solar panels, then getting an energy storage solution is the next natural step for many reasons, as you can:

  • Use 100% of the power you generate – so none is wasted!
  • Reduce your energy bills, by using solar power even after the sun has set
  • Cut the amount of greenhouse gases being released into the atmosphere by using your own renewable energy
  • Become less reliant on the grid, and help to build a smarter, more flexible energy system
  • Make money with the Smart Export Guarantee 
  • Use your battery to store grid energy at off-peak times to use during peak times (if you have an Economy 7 or other time of use tariff – where you get a different unit price at certain times of day). 

What about the disadvantages? 

Unfortunately, it’s not all sunshine. Here are a few of the disadvantages to consider before you take the plunge:

  • Batteries can be quite expensive to buy and install
  • Not all homes are suitable for battery storage, as they need certain conditions, such as enough space and ventilation, to work properly
  • The lifespan of a battery system is currently around 10 years, which means you’ll probably need to replace it at least once during the lifetime of your  solar panels
  • Some lead-acid batteries need special maintenance, and can be dangerous if not handled correctly

Should I buy a battery at the same time as my solar panels?

solar panels on a home

If you’re planning on installing solar panels, it would be a good idea to install a battery at the same time. 

This is because if you buy a battery as part of a solar panel installation, you can benefit from paying only  5% VAT on the whole system. But if you install solar panels and get a battery later, as part of a retrofit, you’ll pay 20% VAT on the battery. 

Is solar battery storage right for my home?

If you already have PV solar panels, or are planning to install them, then having a home energy storage system could make perfect sense. You’ll be able to maximise the amount of solar energy you generate, and could even go off-grid altogether – meaning lower, or even no energy bills! For example, if you’re out at work all day, you could harness the sun’s solar power and store it for when you get home. 

Time of use tariffs, such as Economy 7, mean you could also use your battery to store up cheaper nighttime power and use it during peak times. 

But battery storage isn’t for everyone at the moment. If you’re at home all day, for example, and are already using a lot of the energy you’re generating, then a battery might not be worth the investment. 

An energy storage system can cost over £1200, so you need to be sure it makes financial sense for you. Remember, checking your home is as energy-efficient and as insulated as possible can make a big difference to your energy bills too. 

How much could I save with solar battery storage? 

How much is it really possible to save? Whether you’ll be able save money with battery storage depends on various factors:

  • The cost of the system you install (ranging from £1200 to £60001)
  • The size of your PV system
  • How much energy your home uses
  • How you use your battery 
  • The price of electricity and the tariff you’re on
  • The battery’s lifespan

If you’re seriously thinking about solar battery storage, it’d be prudent to get several written quotes from installers who are approved by the Microgeneration Certification Scheme (MCS) . They'll be able to tell you not only the cost of the installation, but also the potential savings. 

How many solar panels and batteries are needed to power a house? 

This depends of course on the size of your house, and your energy use. A large 4 bedroom family home with 6 occupants will need more solar panels, and a bigger battery, than a single person living in a studio apartment. 

The Microgeneration Certification Scheme (MCS) has created a standard method to estimate performance, but it’s not an exact science. For a more exact figure, you’d have to get a quote from an installer. 

To find out more about how much solar energy it takes to boil a kettle or run your fridge for a month, read our practical guide on domestic solar panels

How much solar battery storage do I need?

A very good question! It depends on 2 things:

  1. How much energy you produce: how much power does your solar PV system supply to your home? 

  2. What you want to use the power for: do you only want to have as much power as you’ll use? Or do you want as big a battery as possible, so you can charge it during off-peak times, and sell energy back to the grid at peak times? 

    To work out exactly what size battery you need, it’s best to call in a professional. This way you can be sure you’re not under- or overestimating the storage you need. 

The cost of solar battery storage systems in the UK 

There’s a huge range of battery systems available, at varying prices. This table from Greenmatch gives a general idea of what you can expect to pay for a Lithium-ion battery – the most mainstream and cost-effective battery choice:

Usable Capacity (kWh)Estimated Price (Lithium-ion batteries)
3-4 kWhFrom £3,410
4-7 kWhFrom £4,288
7-9 kWhFrom £5,185
9 - 13.5 kWhFrom £5920

Are there government grants available for solar battery storage and installation? 

There are no government grants available for battery storage specifically, but there are various incentives available for solar panel installation: 

  • Renewable Heat Incentive – this applies only to solar water heating
  • Smart Export Guarantee – to make money for the power you generate and export back to the Grid
  • Reduced VAT – in most circumstances, 5% tax discount is available on solar panels

Solar battery storage products: OVO’s top 4 best energy storage systems 

1. Powervault 3

Powervault is a British company, and is the one we chose to run our home energy storage trial

  • Price: £3299 (4kWh) or £4999 (8kWh)
  • Size in kWh: 4kWh or 8kWh
  • Physical size: 97 x 100 x 25cms (4kWh)
  • Weight: 129kg (4kWh) 179kg (8kWh)
  • Warranty: 10 years
  • Key feature: Can monitor performance online and provide grid services.

2. Duracell

You might know this brand more for its AAs and AAAs, but the gold-topped battery is a leader in home energy storage too.

  • Price: £4499
  • Size in kWh: 3.3
  • Physical size: 68 x 26 x 61cms 
  • Weight: 3.3kg
  • Warranty: 10 years
  • Key feature: Can monitor solar panel and battery performance through an app. Can provide grid services.

3. Tesla 

You might not be able to afford their Roadster electric car, but their battery storage is a bit more affordable. 

  • Price: £6200
  • Size in kWh: 13.5
  • Physical size: 74 x 111 x 14cms
  • Weight: 125kgs
  • Warranty: 10 years
  • Key feature: can monitor performance through an app.

4. GivEnergy

These batteries offer great quality and flexibility at an affordable price.

  • Price: £5330
  • Size in kWh: 8.2
  • Physical size: 62 x 48 x 22cms
  • Weight: 74kg
  • Warranty: 10 years
  • Key feature: small, lightweight, and modular.

Things to consider before installing a home energy storage system

Can solar panels work without battery storage?

Absolutely! For everything you need to know about solar panels, check out our guide. They work perfectly on their own; batteries help to maximise the energy they generate. 

Do I have to have solar panels to install a battery?

Home battery storage isn’t only for solar panel owners! It can also work with other renewable energy generators, or it can be used to store energy from the grid at off-peak prices if you have an Economy 7 or other time of use tariff. Then you never need to use energy at peak prices again. Batteries can also be used if you drive an electric car

How big are solar batteries?

Just as with mobile phones, as technology develops, battery size decreases. Nowadays home energy batteries range from about the size of a laptop, to the size of a dishwasher. 

Of course, if you need more capacity, the bigger it gets. So if you have a garage, utility room or even space under the stairs, you may be able to house a battery. 

Can I have the battery in the loft?

Yes, but it’s not always advisable. Why? Because many batteries are over 50kg, installation can be difficult, and ventilation can also be a problem. You’d also have to install a fixed ladder and boarding to the position of the battery, which might not be convenient in smaller homes.

In summary, is it worth getting a solar battery?

This all depends on how much energy you’re generating, and if you have a lot of excess that you need to store. For big homes, with occupants who are mostly out during the day and home in the evening, it makes more sense. 

It’s worth considering that battery prices will drop, so if you’re thinking about it now, why not get a few quotes, and then keep an eye on the market?

Go one step greener with OVO Beyond

As an OVO member, you already get 100% guaranteed renewable2 electricity3, and a tree planted every year in your name. Are you ready to go one green step further? With OVO Beyond, our green upgrade, you get all that plus:

  • 100% carbon-neutral gas4, including 15% green gas5 (that’s one of the best fuel mixes around!)

  • Not 1, but 5 carbon-busting trees planted in the UK on your behalf6

  • Personally customised Energy Spotlight tips that’ll help you cut 10% off your bills7

    Plus, you’ll be supporting our carbon-offsetting projects that:

  • Save rainforests in Guatemala

  • Plant trees in Uganda

    And you’ll bring the UK’s children a breath of fresh air in urban areas, by supporting our charity partner Earthwatch Europe, as they plant 8 Tiny Forests across our nation. That’s like covering an area the size of 8 tennis courts with 600 trees each! 

    Going “Beyond” means you can cut your carbon footprint by a further 28%8! All this for just £6 a month. 

    Together we can make zero carbon possible. 

Sources and References:

1 https://www.greenmatch.co.uk/blog/2018/07/solar-battery-storage-system-cost

2 The renewable electricity we sell is backed by renewable certificates (Renewable Energy Guarantee of Origin certificates (REGOs)). See here for details on REGO certificates and how these work.

3  Each year, OVO plants 1 tree for every member in partnership with the Woodland Trust. Trees absorb carbon dioxide from the atmosphere, so tree-planting helps to slow down climate change.

4 Enjoy even greener energy with OVO Beyond in comparison with our standard OVO plans. In addition to 100% renewable electricity as available with our standard plans, OVO Beyond reduces your yearly carbon emissions from the energy used in your home that is supplied by OVO to net zero by providing 100% carbon-neutral gas (15% green gas and 85% offset) and offsetting all associated lifecycle carbon emissions involved in the production and consumption of your electricity & gas, you will also get 5 trees per year in UK schools and communities and other green benefits. The renewable electricity we sell is backed by renewable certificates (Renewable Energy Guarantee of Origin certificates (REGOs)). See here for details on Renewable Energy Guarantee of Origin certificates and how these work. The green gas we sell is backed via renewable certificates (Renewable Gas Guarantees of Origin (RGGOs)). See here for details on Renewable Gas Guarantees of Origin and how these work. We offset the remaining emissions by supporting UN REDD+ carbon reduction projects that are certified to the Verified Carbon Standard or the Gold Standard. See here for more information on how we restore nature and protect rainforests with our offsetting programmes.

5 OVO Energy's Green Gas is made up of 15% green gas, with the remaining 85% offset to make your gas carbon-neutral. As of 31st July 2020, the proportion of biogas offered vs. the amount offset was higher than all other providers who share details of their green gas offering, except Green Energy UK - and that's something we're pretty proud of. The green gas we sell is backed by renewable certificates (Renewable Gas Guarantees of Origin (RGGOs)).  See here for details on Renewable Gas Guarantees of Origin and how these work. We offset the remaining emissions by supporting UN REDD+ carbon reduction projects that are certified to the Verified Carbon Standard.

6 OVO plants 5 trees for every OVO Beyond member through our  award-winning I Dig Trees programme with The Conservation Volunteers. Trees absorb carbon dioxide from the atmosphere, so tree-planting helps to slow down climate change. Since 2015 we have planted over 1 million trees.

7 Savings of up to 10% are based on an estimated reduction in energy use for a dual fuel medium user (3100 kWhs electricity and 12000 kWhs gas) who upgrades to OVO Beyond without having a smart meter or smart thermostat installed yet. Savings are (1) calculated on this estimated reduction in energy use in the first year of having OVO Beyond, and (2) based on reducing your energy use by using your smart meter In-Home Display (IHD) and the OVO app to make changes to your energy habits (like optimising heating settings, switching lights off). Savings are an estimate only and your actual savings will vary depending on your energy use and the changes you make to your energy habits.

8 Based on analysis carried out by the Carbon Trust for OVO Group (2020), 28% of an average individual’s carbon footprint in the UK comes from energy. In this analysis, the carbon footprint includes the following lifestyle categories: energy, transport, shopping, food and drink and holidays. See table below for each category. This carbon footprint data has been calculated using BEIS 2020 emission factors. This excludes emissions from things that the average person cannot directly control such as supporting the NHS, defence, government bodies, etc. Please note these figures are not reflective of potential changes to your habits during the coronavirus pandemic.

UK average individual carbon footprint breakdown

Lifestyle area

Total UK average individual carbon emissions (kgCO2e/year)

Contribution to total (Highest available green gas offering (as of 31st July 2020)

Energy

1,640, 28%

Transport

1,363, 23%

Food and Drink

981, 17%

Shopping

1,189, 21%

Holiday

629, 11%

Total

5,802, 100%

Things to consider before installing a home energy storage system

Absolutely! For everything you need to know about solar panels, check out our guide. They work perfectly on their own; batteries help to maximise the energy they generate. 

Home battery storage isn’t only for solar panel owners! It can also work with other renewable energy generators, or it can be used to store energy from the grid at off-peak prices if you have an Economy 7 or other time of use tariff. Then you never need to use energy at peak prices again. Batteries can also be used if you drive an electric car

Just as with mobile phones, as technology develops, battery size decreases. Nowadays home energy batteries range from about the size of a laptop, to the size of a dishwasher. 

Of course, if you need more capacity, the bigger it gets. So if you have a garage, utility room or even space under the stairs, you may be able to house a battery. 

Yes, but it’s not always advisable. Why? Because many batteries are over 50kg, installation can be difficult, and ventilation can also be a problem. You’d also have to install a fixed ladder and boarding to the position of the battery, which might not be convenient in smaller homes.

In summary, is it worth getting a solar battery?

This all depends on how much energy you’re generating, and if you have a lot of excess that you need to store. For big homes, with occupants who are mostly out during the day and home in the evening, it makes more sense. 

It’s worth considering that battery prices will drop, so if you’re thinking about it now, why not get a few quotes, and then keep an eye on the market?

Go one step greener with OVO Beyond

As an OVO member, you already get 100% guaranteed renewable2 electricity3, and a tree planted every year in your name. Are you ready to go one green step further? With OVO Beyond, our green upgrade, you get all that plus:

  • 100% carbon-neutral gas4, including 15% green gas5 (that’s one of the best fuel mixes around!)
  • Not 1, but 5 carbon-busting trees planted in the UK on your behalf6
  • Personally customised Energy Spotlight tips that’ll help you cut 10% off your bills7

Plus, you’ll be supporting our carbon-offsetting projects that:

  • Save rainforests in Guatemala
  • Plant trees in Uganda

And you’ll bring the UK’s children a breath of fresh air in urban areas, by supporting our charity partner Earthwatch Europe, as they plant 8 Tiny Forests across our nation. That’s like covering an area the size of 8 tennis courts with 600 trees each! 

Going “Beyond” means you can cut your carbon footprint by a further 28%8! All this for just £6 a month. 

Together we can make zero carbon possible. 

Sources and References:

1. https://www.greenmatch.co.uk/blog/2018/07/solar-battery-storage-system-cost

  1. The renewable electricity we sell is backed by renewable certificates (Renewable Energy Guarantee of Origin certificates (REGOs)). See here for details on REGO certificates and how these work.

3 . Each year, OVO plants 1 tree for every member in partnership with the Woodland Trust. Trees absorb carbon dioxide from the atmosphere, so tree-planting helps to slow down climate change.

  1. Enjoy even greener energy with OVO Beyond in comparison with our standard OVO plans. In addition to 100% renewable electricity as available with our standard plans, OVO Beyond reduces your yearly carbon emissions from the energy used in your home that is supplied by OVO to net zero by providing 100% carbon-neutral gas (15% green gas and 85% offset) and offsetting all associated lifecycle carbon emissions involved in the production and consumption of your electricity & gas, you will also get 5 trees per year in UK schools and communities and other green benefits. The renewable electricity we sell is backed by renewable certificates (Renewable Energy Guarantee of Origin certificates (REGOs)). See here for details on Renewable Energy Guarantee of Origin certificates and how these work. The green gas we sell is backed via renewable certificates (Renewable Gas Guarantees of Origin (RGGOs)). See here for details on Renewable Gas Guarantees of Origin and how these work. We offset the remaining emissions by supporting UN REDD+ carbon reduction projects that are certified to the Verified Carbon Standard or the Gold StandardSee here for more information on how we restore nature and protect rainforests with our offsetting programmes.

5. OVO Energy's Green Gas is made up of 15% green gas, with the remaining 85% offset to make your gas carbon-neutral. As of 31st July 2020, the proportion of biogas offered vs. the amount offset was higher than all other providers who share details of their green gas offering, except Green Energy UK - and that's something we're pretty proud of. The green gas we sell is backed by renewable certificates (Renewable Gas Guarantees of Origin (RGGOs)).  See here for details on Renewable Gas Guarantees of Origin and how these work. We offset the remaining emissions by supporting UN REDD+ carbon reduction projects that are certified to the Verified Carbon Standard.

  1. OVO plants 5 trees for every OVO Beyond member through our  award-winning I Dig Trees programme with The Conservation Volunteers. Trees absorb carbon dioxide from the atmosphere, so tree-planting helps to slow down climate change. Since 2015 we have planted over 1 million trees.

  2. Savings of up to 10% are based on an estimated reduction in energy use for a dual fuel medium user (3100 kWhs electricity and 12000 kWhs gas) who upgrades to OVO Beyond without having a smart meter or smart thermostat installed yet. Savings are (1) calculated on this estimated reduction in energy use in the first year of having OVO Beyond, and (2) based on reducing your energy use by using your smart meter In-Home Display (IHD) and the OVO app to make changes to your energy habits (like optimising heating settings, switching lights off). Savings are an estimate only and your actual savings will vary depending on your energy use and the changes you make to your energy habits.

  3. Based on analysis carried out by the Carbon Trust for OVO Group (2020), 28% of an average individual’s carbon footprint in the UK comes from energy. In this analysis, the carbon footprint includes the following lifestyle categories: energy, transport, shopping, food and drink and holidays. See table below for each category. This carbon footprint data has been calculated using BEIS 2020 emission factors. This excludes emissions from things that the average person cannot directly control such as supporting the NHS, defence, government bodies, etc. Please note these figures are not reflective of potential changes to your habits during the coronavirus pandemic.

UK average individual carbon footprint breakdown

Lifestyle area: Total UK average individual carbon emissions (kgCO2e/year)

Contribution to total (Highest available green gas offering (as of 31st July 2020)

Energy: 1,640, 28%. Transport: 1,363, 23%. Food and Drink: 981, 17%. Shopping: 1,189, 21%. Holiday: 629, 11%. Total: 5,802, 100%

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