Can I add a battery to my existing solar panels?

Yes. AC-coupled retrofits work with any existing solar inverter and avoid replacing it — ask installers for current pricing, since AC-coupled kit typically costs more per kWh than fitting a hybrid inverter and battery together at install time. They're also slightly less efficient than hybrid systems (some round-trip losses at the extra conversion stage).

How long do solar batteries last?

Lithium iron phosphate (LFP) batteries — what nearly all 2026 home batteries use — are warranted for 10 years or 6,000 cycles. Real-world degradation is 2–3% per year, so expect 80% of original capacity at year 10.

Do batteries work in a power cut?

Only if you specifically buy a battery with EPS (Emergency Power Supply) and have it wired to a backup circuit. Most installs aren't wired this way by default — ask the installer to quote it explicitly if power-cut backup matters to you.

Solar battery storage cost (UK 2026)

Battery prices, sizing logic, and an honest take on when home storage pays back — and when it doesn't.

How much does a home solar battery cost in 2026?

There is no official UK dataset tracking installed home-battery prices (unlike solar PV, which DESNZ publishes via MCS data), so any specific £ or £/kWh figure you see quoted is somebody's estimate, not a verified average. What's true directionally: price scales with useable capacity, an all-in-one unit with a built-in inverter (like Tesla Powerwall 3) typically commands a premium over a battery-plus-separate-inverter setup (like Pylontech or GivEnergy modules), and AC-coupled retrofits onto an existing solar inverter usually cost more per kWh than fitting the battery at the same time as a new hybrid inverter.

Get current fitted quotes from at least two MCS-certified installers — battery pricing moves with cell costs, exchange rates and installer promotions more than solar panel pricing does, so a quote from even a year ago is not a reliable guide.

How to size a battery for your home

The rule of thumb: size the battery to your evening consumption, not your full daily use. A typical 3-bed semi uses 8–12 kWh per day, but only 3–5 kWh of that lands between 5pm and 10pm when the panels aren't producing.

A 5 kWh battery covers most evenings for a small household. A 10 kWh battery covers a family with an EV charging overnight. Anything bigger usually means you're trying to make the battery do something it isn't good at — like full off-grid living.

When the maths actually works

A battery saves you the spread between the import rate (26p/kWh on the current Ofgem cap) and the export rate you'd otherwise be paid — anywhere from about 1p to 25p/kWh depending on the SEG tariff (Which?, April 2026). A 5 kWh battery doesn't cycle fully every day across a UK year, since generation is heavily skewed to summer, so the realistic annual saving on solar surplus alone is well short of the theoretical maximum implied by multiplying capacity by 365 days.

On a high-export tariff — Good Energy at 25p or Intelligent Octopus Flux at 23p, for example — the import/export spread narrows sharply and battery payback on solar surplus alone stretches out considerably. On those tariffs the cleverer play is often to export more and spend the battery budget on a cheap overnight import tariff instead.

Brands worth paying for, and ones to skip

Tier 1 (proven 10-year performance, well-stocked spares): Tesla, GivEnergy, Fox ESS, SolarEdge.

Tier 2 (cheaper, decent reliability, smaller installer network): Pylontech, BYD, Sunsynk.

Skip: any battery with no UK importer, no UKCA marking, or a warranty that excludes 'commercial use' but defines that term loosely. We've seen warranty claims rejected on perfectly normal residential systems.

Frequently asked questions

Can I add a battery to my existing solar panels?: Yes. AC-coupled retrofits work with any existing solar inverter and avoid replacing it — ask installers for current pricing, since AC-coupled kit typically costs more per kWh than fitting a hybrid inverter and battery together at install time. They're also slightly less efficient than hybrid systems (some round-trip losses at the extra conversion stage).
How long do solar batteries last?: Lithium iron phosphate (LFP) batteries — what nearly all 2026 home batteries use — are warranted for 10 years or 6,000 cycles. Real-world degradation is 2–3% per year, so expect 80% of original capacity at year 10.
Do batteries work in a power cut?: Only if you specifically buy a battery with EPS (Emergency Power Supply) and have it wired to a backup circuit. Most installs aren't wired this way by default — ask the installer to quote it explicitly if power-cut backup matters to you.