Solar panel battery storage – EQ Mag Pro

Find out about solar panel battery storage, including what’s on offer, if you need solar panels to install one and whether you should get one.

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.

This relatively new technology may be worth considering if you generate your own energy at home with solar panels but could use more of it outside daylight hours – or plan to start doing so.

Read on to find out about different energy-storage products, how much they cost, and the pros and cons of batteries. Or jump straight to our table of the latest home batteries.

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 energy bills. If your home is off-grid, it can help to reduce your use of fossil fuel back-up generators.

Even without solar panels, you may be looking to make use of time-of-use tariffs with a battery. These 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, and we expect to see more of them as they can help to balance energy supply and demand, and reduce the need for additional fossil-fuel generation at peak times.

If, for example, it’s a windy night and lots of wind turbines are generating electricity for the grid that no-one is using, it makes sense to make the most of that with battery storage.

Home-energy storage will cost you upwards of £2,000, so you’ll need to make sure your investment is worthwhile.

If you’re at home during the day and already use a large proportion of the electricity you generate through solar panels, 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 upwards of £2,000, so you’ll need to make sure it’s a worthwhile investment and you’ll get your money back on your energy bills. With grid electricity currently very expensive, the pay back times might now be quicker than you think.

If you’re looking to save money by installing energy storage, read on for our first impressions of energy-storage systems available now.

What size solar storage battery do I need?

The average home uses around 8kWh of electricity per day. The capacity of new lithium-ion batteries ranges from around 1kWh up to as much as 15kWh.

Ideally, you want a battery that will cover your evening and night-time electricity usage, ready to be charged up again when the sun comes up. You’ll also need to bear in mind how much your solar panels can generate, as there’s no point buying a battery that’s bigger than they can fill.

With a battery that is well chosen for your home’s energy use and your solar panels’ output, you should find that you can have enough electricity to serve your evening needs for most of the year. You might find that you are still drawing on grid electricity for some of the longest winter nights.

You’ll need to speak to a battery installer to discuss what will be the right size for your home.

Can I save money with a solar battery?

When we surveyed Which? members in 2019 about their solar panels, 106 of our 1,987 survey respondents had battery storage. 25% paid less than £3,000 for their battery system, while 41% paid between £4,000 and £7,000 (excluding the cost of the PVs themselves).

Installing a home-energy storage system is a long-term investment to make the most of your solar-generated energy and help cut your energy bills.

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 battery systems come with a 10-year warranty. They require little maintenance, so the main cost is the initial installation. However, solar PV panels can last 25 years or more, so you should factor in the cost of replacing the battery at least once into your total costs.

Batteries are expensive to buy, but prices are dropping all the time, as are solar panel prices. With electricity prices at record highs, the payback times are improving.

Some battery 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 (time-of-use, or TOU tariff) and, if you generate your own electricity, how much of this you use already.

If you get the Feed-in Tariff (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 have a smart meter, 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 Smart Export Guarantee (SEG) tariffs mean that energy firms will pay you for any excess renewable electricity you have generated and export to the grid. All suppliers with more than 150,000 customers have to offer them, but the rates are not very generous.

Compare rates to find the best for you – but check that you’re eligible if you have storage installed.

Financing energy storage

While battery prices are coming down, it’s still a significant investment.

The best option is to pay for your battery upfront using your own savings. If you don’t have the cash to do this, you could consider a loan. However, remember you’ll have to pay interest on money you borrow, so make sure that gains made from battery 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 Energy Saving Trust Home Energy Scotland to find out more.

Tesla, Samsung, EDF, E.on and Ovo home energy storage packages

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.

EDF Energy sells 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’.

Eon is selling batteries alongside solar panels so that customers can store excess electricity generated, or charge their electric vehicle. It also pays its customers for excess electricity they export to the grid.

Ovo 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.

Battery storage products

The batteries below 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. Some companies offer ‘stackable’ batteries that can be used together.

Use the table to compare prices, capacities and key features.

Energy storage systems round-up
Product	Price (excl. installation)	Size (cm)	Weight (kg)	Capacity	Warranty	Key features	Availability
Duracell Energy Bank	£4,499	68 x 26 x 61	96	3.3kWh	10 years	You can monitor electricity generation and storage via an app. Ability to trade with the grid.	Available from Duracell.
Enphase AC Battery	£1,699	39 x 33 x 22	23	1.2kWh	10 years	Enphase Enlighten software shows you energy production and consumption.	Available via UK installers.
LG Chem Resu	£5,545+	44 x 43 x 10	33	3.3kWh	Up to 10 years	Can be wall or floor-mounted.	Via Eon surveyors.
Moixa Smart Battery (AC)	£2,950 – £3,450 (including installation)	51 x 35 x 25	40 or 49	2kWh or 3kWh	10 years (extendable for Gridshare members)	Moixa will pay £50 per year to trade excess power stored in your battery using web-connected GridShare.	Available direct from Moixa.
Nissan xStorage	£5,550+	122 x 89 x 22	135	4.2kWh and 6kWh	5-10 years	Batteries are re-used from Nissan electric vehicles. Home energy management app tracks energy storage and consumption.	Available from Nissan.
Powervault 3	£3,229 (4kWh) £4,999 (8kWh)(all excl VAT)	97 x 100 x 25 (smallest model)	129kg (4kWh) to 179kg (8kWh)	4kWh and 8kWh	10 years	Online portal monitor performance charging. Inbuilt capability to provide grid services.	Available from Powervault, UK installers and distributors.
Samsung SDI All-in-one	£5,500	100 x 27 x 68	95	3.6kWh	5 years	Monitoring system detects errors and lets you control the battery remotely. Accessible online and mobile.	Available in the UK.
SolaX Battery System	£1,920+	33 x 45 x 11	26 or 44	3.3 kWh or 6.5kWh	10 years	The Solax portal lets you monitor your system remotely and decide which items to power.	Available via UK installers.
Tesla Powerwall	£6,200	74 x 111 x 14	125	13.5kWh	10 years	The Tesla App allows you to monitor your system.	Available direct from Tesla.
Varta Pulse 3 and 6	£3,729+ (exlc VAT)	60 x 69 x 19	45 and 65	3.3kWh and 6.5kWh	10 years	Varta’s Storage App lets you monitor and control your system remotely.

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.

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, 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 Renewable Energy Consumer Code (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.

Meanwhile the Microgeneration Certification Scheme (MCS) is developing certification for battery storage systems. It says this will ensure consumer protection.

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, as smart meters will make it easy for energy companies to see exactly when you’ve used energy. Economy 7 and Economy 10 are types of traditional 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.

However, charging and discharging is less efficient, so could affect your feed-in tariff. DC systems aren’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/DC power unit to convert the electricity you generate into AC you can use in your home (and 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

If you’re installing a storage system, you should notify your local Distribution Network Operator – check with the Energy Networks Association if you’re not sure who it is. You may also need to inform your local council.

Beware of pressure selling. Check our solar panels buying advice for things to look out for, including rapidly reducing quotes and lack of detailed information.

Solar panel battery storage: pros and cons

Pros:

• 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.

Cons:

• 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 0% VAT until 2027.
• We asked solar-panel experts and owners for their top tips. Find out how to make the most of your solar panels.

*Online survey of 1,567 Which? members who have solar PV and have or would consider a home-battery system, May 2019.

Source: which