Battery · 5 min read
How home battery storage works.
A home battery stores electricity so you can use it later — either solar you generated during the day or cheap off-peak grid electricity overnight. Whether one earns its keep depends less on the hardware and more on your tariff and daily routine.
Key things to consider
Pairing with solar vs standalone
With solar, a battery captures what you would otherwise export cheaply. Standalone, it relies entirely on a time-of-use tariff like Octopus Go or Cosy to charge cheaply overnight and discharge at peak times.
Sizing it correctly
Most UK homes are well served by 5–10 kWh of usable capacity. Going bigger only helps if you genuinely use the energy — oversizing extends payback.
Installation location
Batteries are typically wall-mounted in a garage, utility room or loft. They need ventilation, a stable temperature, and easy access for the inverter.
Pros
- Use more of your own solar instead of exporting it
- Shift grid usage to cheap overnight rates
- Some systems offer backup during power cuts
- Quiet, low-maintenance hardware
Cons
- £3,500–£7,000 upfront for a quality system
- Payback is highly tariff-dependent
- Capacity degrades slowly over 10–15 years
- Not every property has a suitable install location
What it actually costs
Typical install cost
A 5kWh battery fitted to an existing solar system usually costs £3,500–£5,000. Larger 10kWh systems sit around £6,000–£7,500.
Realistic payback
On a time-of-use tariff, most homes see payback in 7–11 years. Standalone batteries without solar typically need a cheap overnight rate to make sense.
FAQs
Will a battery keep my lights on in a power cut?
Only if it is specifically wired for backup, known as an EPS or whole-home backup. Most standard installs do not include this by default.
How long do home batteries last?
Most modern lithium batteries are warranted for 10 years and around 6,000 cycles, retaining 70–80% of their original capacity at the end.
Can I add a battery to existing solar?
Yes. AC-coupled batteries can be retrofitted to any existing solar system without replacing the original inverter.
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