Battery storage as part of a solar system

A DC-coupled battery connects to a hybrid inverter that manages both the panels and the battery. Energy from the panels goes into the battery without being converted twice, which is slightly more efficient, and there is one inverter to maintain. This is the usual choice when panels and battery are installed together, or when the existing inverter is due for replacement anyway.

An AC-coupled battery has its own inverter and connects on the household side, next to the existing solar inverter. It leaves the solar system untouched, which is why it is common when a battery is added to panels that are already working well. The trade-off is an extra conversion step and a second inverter.

Neither is better in every case. The installer should explain which suits your existing equipment, and why.

Usable capacity, measured in kWh, is how much energy the battery can deliver; power, in kW, is how much it can deliver at once. A battery that is too small fills by late morning and exports the rest of the day; one that is too large rarely fills in winter and sits half-empty for months. A sensible size comes from your evening and overnight use and from what your panels actually produce in spring and autumn, not from the largest model the inverter supports.

Tariffs change the answer. On a time-of-use tariff, a battery can also charge from the grid at cheap overnight rates and discharge at peak times, even in winter when the panels produce little. Ask the installer to model both solar-only and tariff charging, using your half-hourly data if you have a smart meter.

Adding a battery changes what your home could export, so the network operator has to be told. Depending on the combined capacity of panels and battery, the installer either connects and notifies, or applies before installing. Where the network has little spare capacity, the operator may approve the connection only with an export limit, which the inverter then enforces.

If your panels earn Feed-in Tariff payments, Ofgem requires you to tell your FIT licensee when battery storage is connected to the accredited installation. The battery must not distort the generation meter reading, so the installer has to connect it in the right place.

Smart Export Guarantee suppliers pay for exported renewable electricity. If your battery also charges from the grid, the export meter may record electricity that did not come from the panels, and the supplier can refuse to pay for it, pay for all of it, or ask for extra metering. Check your supplier's approach before choosing grid charging.

Home batteries hold a lot of energy in a small box, so position matters. The British Standards Institution publishes PAS 63100, which sets fire safety requirements for installing battery storage in homes, and a competent installer follows it when choosing a location. Garages, utility rooms and outside walls are common positions; the survey should explain why the proposed spot is acceptable and what ventilation, clearances and cable routes it needs.

Batteries fitted in homes are zero-rated for VAT until 31 March 2027, whether added to existing panels, installed with new panels, or installed on their own to store grid electricity.

Source: gov.uk

• battery model, usable capacity in kWh and charge and discharge power in kW
• AC or DC coupling, and whether your existing inverter stays
• proposed location and how it meets fire safety requirements
• whether the battery can supply some circuits during a power cut, and which ones
• network notification or application, and any export limit
• effect on any Feed-in Tariff or Smart Export Guarantee arrangement
• warranty in years and in cycles or throughput, and what happens at the end of it

Tell us what panels you have, or plan to have, and how you use electricity, then confirm your mobile number by code and your email by link. Installers in your area see the job without anything that identifies you, and exactly one of them can buy it. It then leaves the shop. The installer pays Offrano, not you.

We email you the installer's name, address and phone number before it gets your details. There is no promise that anyone buys the request; if nobody does within 21 days it is withdrawn, and you are free to look elsewhere. Offrano only checks that the buyer is a registered business, so confirm its MCS certification for battery storage yourself.