Solar batteries and export

Two different ways to use spare solar power

Solar panels make most of their power around midday. Your home often needs more power in the morning and evening. That gap leaves you with two choices for the spare power.

You can store it in a battery for later. Or you can send it to the grid and be paid for it through the Smart Export Guarantee (SEG). Many homes do some of both, since the two choices work well together.

Neither choice is automatically right. A battery costs money up front, but export payments are low in many cases. The better route depends on your tariff, your habits and your budget, so work through the sums before you buy.

For the basics of how a system makes and moves power, see how solar panels work.

What a battery does, and what it does not

A battery charges when your panels make more than you need. It releases that power when you need it, usually in the evening, because that is when demand peaks. This raises the share of solar power you use yourself, which is called self-use.

A battery does not make more power. It also does not cut bills by itself. Because it only shifts power in time, the saving depends on the gap between what you pay for grid power and what you earn for export.

Some limits are worth knowing. However, capacity is not the same as usable capacity. MoneySavingExpert notes that modern batteries commonly allow 85% to 95% of their stated size to be used. So an 8 kWh battery gives about 6.8 to 7.6 kWh in practice.

Our post on solar battery cost and sizing shows how to pick a size. It also explains why a bigger battery is not always better value, because extra capacity may sit unused.

What a battery costs, and when it pays back

MoneySavingExpert (updated 1 October 2026) says a standard 5 kWh battery typically costs about £5,000, while Energy Saving Trust puts a 5 kWh system at around £4,600. Both give a range from about £1,500 to £10,000. MoneySavingExpert also reports that the same battery costs less when you buy it with new panels.

Payback is where many sales claims go wrong. MoneySavingExpert gives a simple test. A £5,000 battery that lasts about 15 years must save around £330 a year just to break even. On a standard tariff, many homes save less than that.

A battery looks better in some homes. MoneySavingExpert says the case is stronger for households on Economy 7 or other time-of-use tariffs, and for electric vehicle owners. These homes can charge cheaply or use more power in the evening.

Our post on time-of-use tariffs with solar and batteries explains how that works, because the tariff decides when power is cheap. The post on charging an electric car from solar panels covers the car side.

Before you add a battery, ask whether the saving is worth the extra cost. Our post asking whether solar panels are worth it gives a fair way to test this. Our hub on solar panel costs and savings shows how the numbers fit together.

Cheaper ways to use more of your own power

You may not need a battery to raise self-use. Moving the washing machine, dishwasher or hot water to midday often helps, because the sun is strongest then. Our post on using more of your own solar power lists simple steps.

A solar diverter is another option. It sends spare power to your hot water tank, while using power you would otherwise export. Home Energy Scotland notes that a diverter is unlikely to meet all your hot water needs alone. Our post on solar diverters for hot water explains when one makes sense.

Panel count matters here too. A bigger array makes more power in winter, but it also makes more spare power in summer, since output rises with sunshine. Our post on how many solar panels you need helps you match the size to your use.

How the Smart Export Guarantee works

The SEG began on 1 January 2020. It covers solar and other small generators up to 5 MW in Great Britain. Ofgem says all licensed suppliers must declare their SEG status each year, and suppliers with at least 150,000 domestic customers must offer a tariff.

Suppliers set their own rates, contract lengths and payment dates. However, the rate must be above zero. To qualify, your system needs an MCS certificate or equivalent, and a meter that reads exports every half hour with its own export meter number.

Your export supplier does not have to be your import supplier. Some suppliers pay a better rate if you take both from them. Others only pay a flat rate to export-only customers. As an example, on 10 October 2026 the Octopus Energy page showed 4.1p per kWh for its export-only SEG tariff and 12p per kWh on its Outgoing tariff for customers who also import from it.

Rates differ widely because each supplier sets its own. MoneySavingExpert reports a range from 1p to 25p per kWh. So check the rate, the contract length and any conditions before you sign, and compare again each year.

Our post on the Smart Export Guarantee covers how to compare tariffs step by step.

Power cuts and backup

Think about power cuts before you pay for a battery. Many solar systems switch off when the grid fails, because that protects engineers working on the lines. Backup needs a system designed for it, which usually costs more.

Ask the installer what would keep running in a cut, and for how long. Do not rely on backup unless the quote says so in writing.

Rules that affect both batteries and export

Connecting to the grid has its own rules. In Great Britain, small systems up to 3.68 kW per phase follow the G98 route, where your installer tells the network operator within 28 days of switching on. Larger systems usually need approval first. SSEN says these standards cover batteries as well as generators.

Our guide to planning your installation explains the steps. Our post on grid connection rules G98 and G99 goes deeper.

Quotes must also be clear about batteries. The MCS standard (MIS 3002 issue 6.0) says a quote must include the battery datasheet. If it states a self-use figure with a battery, it must say whether the installer holds MIS 3012, the MCS battery standard.

Finally, VAT is a saving. Batteries installed in a home are zero-rated until 31 March 2027, including standalone batteries since 1 February 2024. Read our post on 0% VAT on solar panels and batteries before you set a purchase date.

Choosing the right setup

Start with the panels, because they carry most of the value. Then ask whether a battery adds enough on your tariff to justify its price. Finally, pick an export tariff that suits you.

Ask for the battery price, capacity, usable capacity and warranty in writing. Our guide to choosing an installer lists the checks to make. Compare at least three quotes, and keep the battery on a separate line each time.

Check the date before you decide

Tariffs and rules change often. The figures here were checked on 10 October 2026 against the sources below. Check each supplier page for today’s rates before you apply.