Do you need a battery with solar panels?

The short answer

Not always. A battery earns its place when it moves enough electricity from cheap or free to expensive to pay for itself in a sensible time, or when backup during a power cut matters to you. Whether that’s true depends on how much solar you export, when you use electricity and what tariff you’re on. It isn’t a rule that every solar home needs one, and anyone who tells you otherwise is selling.

What a battery actually does

Without a battery, solar electricity you don’t use straight away is exported to the grid, usually at a much lower rate than you pay to buy electricity back in the evening. A battery stores that surplus and releases it when you need it. On a time-of-use tariff, it can also charge from the grid overnight at a cheap rate and run the house during expensive hours, even in winter when solar output is low.

When a battery tends to pay

• you have solar and export a lot of it every day, because the house is empty at midday
• most of your electricity is used in the evening, after the panels wind down
• you’re on, or can switch to, a tariff with a cheap overnight rate
• you’re adding an electric car or heat pump that will raise demand
• you want some essentials to keep running in a power cut

The Energy Saving Trust makes a fair point: for many households, the decision to fit storage is not purely financial. Using more of your own generation and having backup can be worth something to you that a payback sum doesn’t capture. That’s fine, as long as you know which part is economics and which is preference.

When it’s weaker

• low total electricity use
• a small solar system with little surplus to store
• someone at home using most of the solar during the day anyway
• a flat-rate tariff with no cheap overnight period

In those cases a battery can take a long time to pay back, and the money may do more elsewhere: insulation, a bigger array or simply waiting.

Getting the size right

Batteries are quoted two ways: nominal capacity (the total) and usable capacity (what you can actually draw). Compare usable figures. Too small and you’re importing again by mid-evening; too big and you’ve paid for capacity that rarely gets used. The right size comes from your evening demand and your summer surplus, not from the biggest box available.

A battery isn’t automatic backup

A common surprise: many solar and battery systems switch off in a power cut, for the safety of people working on the grid. Keeping the lights on needs a compatible inverter, a backup gateway and wiring to agreed essential circuits, such as lighting, the fridge and phone charging. How long it lasts depends on the battery’s charge, what the panels are producing and what you run.

Adding one later

You don’t have to decide now. Most solar systems can take a battery later, though compatibility depends on the inverter: a hybrid inverter makes it simplest. If you’re unsure, it’s reasonable to install solar first, see your real export figures for a year, and decide with evidence.

What it costs

Battery prices vary with capacity, brand and whether backup is included. Our current confirmed package prices, with what’s included and what isn’t, are on the battery storage page. 0% VAT currently applies to eligible domestic installations until 31 March 2027; scheduled to rise to 5% from 1 April 2027.

What we do

We look at your consumption and, if you have solar, your generation, and show you what a battery would actually shift, in pounds, not just kilowatt-hours. Then we recommend a size, or recommend waiting. Start your home assessment to find out which applies to you.

Sources

• Energy Saving Trust: Solar panel battery storage
• Energy Saving Trust: Is home energy storage right for me?
• Ofgem: Smart Export Guarantee