Houses and gardens from above at night, windows lit

Home batteries

A home battery sized to your evenings, or none at all.

A battery only pays when enough of your use falls after dark. We price every roof with one and without, side by side, so you can see what it adds.

Get my estimate All the kit
On the example
10 kWh
Adds to the price
£4,500
Sized to
Your evenings

What it does

Stored at midday, used after dark.

Without a battery, whatever the house isn’t using goes to the grid, paid at your export rate. With one, the spare charges the battery first, and the house draws on it in the evening before buying from the grid.

On the example estimate, with a £1,500 yearly bill, the home uses 28 per cent of what the roof makes without a battery and 48 per cent with one. The yearly saving rises from about £1,080 to about £1,230. The payback lengthens from about seven years to about ten, because the battery adds £4,500: £11,700⁠–⁠£13,400 installed, against £7,200⁠–⁠£8,900 without. On its own, the battery adds about £150 a year, so it would take about 30 years to repay by itself. Tariffs and export rates vary by supplier, so yours may differ.

How it’s sized

Capacity matched to your evening use, not the biggest box on the list.

  • 01

    Capacity and usable capacity

    Capacity is what the battery holds. Usable capacity is what it will give you, since many hold some back to protect the cells. Compare usable figures, not headline ones.

  • 02

    Matched to your evenings

    Your estimate prices a 10 kWh battery as a benchmark; the survey and the installer’s quote size it to what you use after dark. A battery bigger than your evenings need is rarely emptied, so part of it sits idle.

  • 03

    The chemistry

    Many home batteries now use lithium iron phosphate cells, known as LFP: a chemistry valued for staying stable and for lasting through years of daily charging.

Battery storage

Battery, or not. We price both.

Panels make most at midday. Most homes use most in the evening. A battery moves one to the other, and whether that pays depends on when you are home, what you pay per unit and what you are paid for export.

What your roof makes What your home uses Stored at midday Used after dark
  • What your roof makes
  • What your home uses
  • Stored at midday
  • Used after dark

Usually worth it when…

  • your evening use is high
  • you’re out most of the day
  • you’re on a time-of-use tariff
  • an electric car charges overnight

Often not when…

  • someone is home through the day
  • the array is small for the house
  • your export rate is already strong

On your estimate, 10 kWh adds £4,500, and we show the payback both ways. The choice stays yours.

See both on your estimate

AC or DC

Two ways to connect a battery, in plain words.

Panels make direct current (DC); your home runs on alternating current (AC). What differs is where the battery joins.

DC-coupled

Best where
The battery goes in with the panels on one hybrid inverter, so roof power charges it before it is converted.
Watch for
Compatibility, because the battery must suit that inverter, which ties the two together if either is replaced.

AC-coupled

Best where
Panels are already on the roof, since the battery brings its own inverter and joins on the house side.
Watch for
The extra conversions, since power changes between DC and AC more often, and each change loses a little.

Living with it

A place for it to live, and a warranty to read.

  • 01

    Garage, utility room or an outside wall

    Somewhere dry, with air around it and within the temperatures the manufacturer allows. Some are built for an outside wall; others must stay indoors. Not every room is suitable, so the survey checks your chosen spot.

  • 02

    The warranty

    The batteries we price carry a ten-year manufacturer’s warranty, with a share of their capacity guaranteed to the end of it. The quote should say what that share is, and whether the cover also ends after a set amount of use.

On the quote

What the installer’s quote should specify.

We check every line of the quote before it reaches you. These are the ones that should never be missing.

Reading a solar quote, line by line Every word on a quote

  • The make and model of the battery
  • Its usable capacity, not only its total
  • AC- or DC-coupled, and the inverter it works with
  • Where it will be fitted
  • The battery priced on its own line

Manufacturers we see on quotes

  • Tesla Powerwall
  • Sigenergy
  • Fox ESS
  • Sunsynk

Named because they turn up on quotes. We sell none of them.

Home batteries · questions

Asked about batteries.

01Is a battery worth it for my home?

It depends on when you’re home, what you pay per unit and what you’re paid for export, which vary by supplier. It’s usually worth it when your evening use is high or you’re out most of the day, and often not when someone is home all day.

02Will a battery keep the lights on in a power cut?

Only if the system is designed to. Many shut down with the grid for safety, and backup for chosen circuits needs extra parts, so say if it matters before the quote.

03Does a battery lose capacity over time?

Yes, slowly, with use and age. That is why the warranty guarantees a share of the capacity to the end of its term.

04Can a battery charge from the grid overnight?

Yes, if it’s set up to. On a time-of-use tariff it can fill at the cheaper overnight rate, which helps in winter when the roof makes least. Rates vary by supplier.

Every question

Keep reading

The rest of the system.

A bungalow with a panelled roof across an evening field

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