Battery Storage: What You Need to Know Before Buying

A battery does not just store energy. It changes how your whole home interacts with the grid. Here is what that means in practice.

Why a battery changes everything

Solar panels generate electricity. A battery decides what happens to it. Without storage, surplus power goes straight to the grid for a few pence per unit. With storage, that power waits until you need it — in the evening, overnight, or during a power cut.

How batteries are sized

Batteries are measured in kilowatt-hours (kWh). The average UK home uses around 8–10 kWh of electricity per day. Modern stackable systems range from 5 kWh right up to 60 kWh — you can start small and add modules later. A common starting point is a 10 kWh battery paired with a 4–6 kWp solar system.

What to look for

Cycle life — how many charge/discharge cycles before capacity drops below 80%.
Warranty — look for 10 years minimum.
Chemistry — LFP (lithium iron phosphate) batteries are safer and longer-lasting than older NMC chemistry.
Compatibility — if you already have solar, confirm inverter compatibility before buying.

Intelligent tariffs and batteries

On time-of-use tariffs like Octopus Flux or Go, a smart battery can charge from the grid overnight at cheap rates and discharge during peak hours. This tariff arbitrage can generate savings even without solar panels.

Is a battery worth it without solar?

Possibly, depending on your tariff. Without solar, all savings come from tariff arbitrage. Run the numbers for your specific usage and rate before committing.