What a battery actually changes

Without storage, electricity you generate and do not use in that moment goes to the grid. A battery holds it instead, so you can use it in the evening when the panels have stopped and the house is busiest. That shift is the entire point.

The number that matters is self-consumption — the proportion of what you generate that you actually use yourself. A battery raises it. How much depends on your household, not on the battery's spec sheet.

Usable versus nominal capacity

Batteries are advertised at nominal capacity but you never get all of it. Usable capacity is the figure to compare, and it is the one a good quotation states. Ask for it explicitly if it is missing.

Hybrid or AC-coupled

A hybrid inverter handles panels and battery in one unit and is the neater answer on a new installation. AC-coupled storage bolts onto an existing system with its own inverter, which is usually the route on a retrofit. Both work; the choice normally follows what is already on the wall.

Chemistry, siting and safety

Most domestic batteries sold in the UK now use lithium iron phosphate. Siting matters: a battery wants a dry, ventilated space within a sensible cable run of the inverter, not a sealed cupboard. Garages, utility rooms and plant cupboards are all common.

Ask your installer which product standards the unit is certified to and what the siting requirements are for that specific model — they are not identical between manufacturers.

Backup during a power cut

Some systems can supply part of the house during an outage through an EPS or backup circuit. Many cannot. It is a specific design decision with extra cost and extra wiring, so if it matters to you, say so before the design is fixed rather than after.

Tariffs

Time-of-use electricity tariffs let a battery charge from the grid when import is cheapest. Whether that is worth doing depends on the tariff you can get and how you use electricity. Nobody can promise you a saving from it in advance, and you should be wary of anyone who does.

Common questions

Will a battery cut my bill to nothing?

No. A battery shifts when you use your own generation; it does not remove your reliance on the grid, particularly through a British winter.

How long do they last?

Warranties are commonly around ten years or a stated cycle or throughput figure. The exact terms vary by manufacturer and will be set out in your quotation.

Can I add one later?

Usually, yes — see battery retrofit. Whether it is straightforward depends on your existing inverter.

What does the quote cost?

Nothing, and there is no obligation. The installer provides a free design and written quotation.

Solar Battery Storage in London