We tell you all you need to know about home-energy batteries (or solar batteries).
From which households can benefit from investing in energy storage, to what types of battery are available, which brands make them, and how much they cost.
What is solar panel battery storage?
An energy-storage system, also called a home or solar battery, lets you capture electricity so you can use it at another time. For example, you can store the electricity your solar panels generate during the day and use it at night.
Big tech brands including Samsung and Tesla sell home-energy storage systems. Energy companies including EDF Energy, Eon and Ovo are also currently selling solar panel and storage packages.
is selling Powervault solar batteries and says customers can get a discount in return for helping EDF balance the grid. It says it’s trying to create a ‘network of small-scale’ batteries to help balance the peaks and troughs of energy production and customer demand’.
is selling batteries alongside solar panels so that customers can store excess electricity generated, or charge their electric vehicle. It is also paying customers for excess electricity they export to the grid.
is selling a home energy storage device which charges from the grid when electricity is cheaper and less carbon-intensive, and discharges it to run appliances when electricity is pricier and more carbon-intensive later.
This relatively new technology may be worth considering if you generate your own energy at home but could use more of it – or plan to start doing so.
Is solar battery storage right for my home?
If you have solar PV panels, or are planning to install them, then using home batteries to store electricity you’ve generated will help you to maximise the amount of renewable energy you use. In fact, 60% of people who have, or would consider, a home battery told us the reason was so they could use more of the electricity generated by their solar panels.*
Home-energy storage will also reduce the electricity you use from the grid, and cut your bill. If your home is off-grid, it can help to reduce your use of fossil fuel back-up generators.
In the near future, time-of-use tariffs will let you store up electricity while it’s cheap (overnight, for example) so you can use it during peak times. A few energy companies have launched these already.
If you’re at home during the day and already use a large proportion of the electricity you generate, or divert surplus electricity to heat your water (for example), then a battery may not be right for you.
This is because home-energy storage will cost you more than £2,000, so you’ll need to make sure it’s a worthwhile investment.
If you’re looking to save money by installing energy storage, like the 17% of Which? members who are interested in home batteries*, read on for our first impressions of energy-storage systems available now.
Can I save money with a solar battery?
Which? members we spoke to typically paid either less than £3,000 (25%) or between £4,000 and £7,000 (41%) for a battery storage system (excluding the cost of solar PV, where relevant). Quoted prices in the table below range from £2,500 to £5,900.
How much Which? members paid for solar batteries
Installing a home-energy storage system is a long-term investment to help cut your energy bills, although this may not be your motivation.
Whether a battery will save you money will depend on:
- the cost of installation
- the type of system installed (DC or AC, chemistry of the battery, connections)
- how it’s used (including the effectiveness of the control algorithm)
- the price of electricity (and how it changes during the lifetime of your system)
- the battery’s lifetime.
Several systems come with a 10-year warranty. They require little maintenance, so the main cost is the initial installation. If you install it with solar PV (which can last 25 years or more), you should factor in the cost of replacing the battery.
While the cost of a battery is high, it’ll take a long time for the battery to pay for itself. But if battery prices drop in future (as with ), and electricity prices increase, then payback times would improve.
Some storage companies offer financial benefits – for example, payments or reduced tariffs for providing services to the grid (eg letting spare electricity from the grid be stored in your battery). If you have an electric vehicle, being able to store cheap electricity to charge it could help to cut your costs.
We haven’t yet tested home-energy storage systems to be able to calculate how much they could cost or save you. However you should take into account whether you are on a tariff which has different electricity costs depending on the time of day and, if you generate your own electricity, how much of this you use already.
If you get the (FIT), part of it is based on the amount of electricity you generate and export to the gird. You’ll need to have signed-up already to receive the FIT as it is closed to new applications. If you don’t have a smart meter the amount of electricity you export is estimated at 50% of what you generate.
If you do have a , your export payments will be based on actual export data. However, if you also have a home battery installed, your export payments will be estimated at 50% of what you generate. This is because your export meter cannot determine whether electricity exported from your battery was originally generated by your panels or taken from the grid.
If you are looking to install solar panels and a solar battery, new will pay you for any excess renewable electricity you have generated and export to the grid. Very few of these exist now but all companies with more than 150,000 customers have to offer them by the end of the year. Compare rates to find the best for you – but check that you’re eligible if you have storage installed.
Financing energy storage
A small proportion of Which? members we spoke to have paid more than £7,000 for their home battery, although a quarter of them paid less than £3,000. However, it’s still a significant investment.
One option is to pay for your battery upfront using savings. But if you don’t have the cash to do this, you may want to consider a loan. However, remember you’ll have to pay interest on money you borrow, so make sure that gains made from storage would outweigh this.
If you live in Scotland, the government offers interest-free loans to homeowners to fund energy-saving improvements, including energy storage. You can borrow up to £15,000, which you must repay within 10 years. See to find out more.
Battery storage products
As a relatively new technology, there is a limited, but growing, range of products. Capacity of new lithium-ion batteries ranges from around 1kWh to 8kWh; a 4kWh system would store enough energy to boil your kettle 37 times, according to the Energy Saving Trust.
If you want a larger capacity, some firms offer ‘stackable’ systems which combine more than one battery.
These range from the size of a small computer to the size of a washing machine. Greater capacity means a bigger and heavier battery. Small systems can be wall-mounted, while larger ones sit on the floor.
Use the table below to compare the latest battery prices, capacities and key features.
Bear in mind that usable capacity is usually less than stated capacity. This is because batteries tend to lose some energy in charging and discharging, and most aren’t designed to be fully discharged on a regular basis.
The products in the table above are designed to work with the grid. If you’re off-grid, speak with an installer directly to get an appropriate system for your situation.
Following the closure of the feed-in tariff scheme in March 2019, Ikea said that it has put its solar offer ‘under review’. It is not currently selling home energy storage.
Before you install a home-energy storage system
Consider whether you’re generating enough electricity that you don’t use to make it worth adding energy storage to an existing solar panel system.
If you’re looking to protect yourself against power cuts with a home battery, as 4% of Which? members with solar panels who own or would consider a battery system told us they are, not all systems are suitable.
Get quotes from several installers on cost of installation and estimated savings. Ask them to explain their calculations to you and question anything you’re not sure about.
Check that your installer is signed up to the (RECC), which now covers storage. This means they’re signed up to a high standard of conduct, including providing good information about your installation. You also have access to RECC’s complaints process if something goes wrong.
Do I have to have solar panels to install a battery?
No. You can charge a home battery using electricity you buy from the grid. If you have a time-of-use electricity tariff you can save money by charging your battery when electricity is cheaper, and using the power from it so you’re not buying from the grid at pricey peak times.
But most people do not have time-of-use tariffs yet. These will become more widely available as smart meters are rolled-out. Economy 7 and Economy 10 are types existing of time-of-use tariffs, usually linked to storage heating systems.
Battery storage installation systems
There are two types of battery installation: DC and AC systems.
DC battery systems
A DC system is connected directly to the generation source (eg solar panels), before the electricity generation meter. You won’t need another inverter, which is more efficient, but charging and discharging is less efficient, so could affect your FIT (this isn’t usually recommended if you’re retrofitting a battery to an existing PV system).
DC systems can’t be charged from the grid, according to the Energy Saving Trust.
AC battery systems
These are connected after the electricity generation meter. So you’ll need an AC-to-DC power unit to convert the electricity you generate into AC you can use in your home (and then back again to store it in your battery).
AC systems are more expensive than DC systems, according to the Energy Saving Trust. But an AC system won’t affect your FITs payments, as the generation meter can register the total system output.
Battery installation tips
Solar panel battery storage: pros and cons
- Helps you use more of the electricity you generate.
- Some firms pay you for allowing your battery to be used to store excess grid electricity.
- Could enable you to take advantage of cheap-rate electricity.
- Require little maintenance: ‘Fit and forget’, said one owner.
- Currently pricey, so payback time may be long.
- A DC system could reduce your FIT payments.
- Likely to need replacing during the lifetime of a solar PV system.
- If retro-fitted to existing solar PV, you may need a new inverter.
- Batteries added to existing solar PV systems are subject to 20% VAT. Batteries installed at the same time as solar panels are subject to 5% VAT.
*Online survey of 1,567 Which? members who have solar PV and have or would consider a home-battery system, May 2019.