Short answer: It doesn't have to. Ofgem's guidance says your FIT generation payments continue if the generation meter only measures what the panels produce. That means the meter sits between the panels and the battery, the battery can't charge from the grid, or an approved meter is fitted. You should report the battery to your FIT supplier.
Why a battery can be a problem for a FIT
Feed-in Tariff payments are based on the generation meter, which counts the electricity your panels produce. Ofgem’s worry is that a battery could make that meter count power that didn’t come from the panels, for example electricity bought cheaply from the grid overnight, stored, and then released through the same meter.
So the rules are about the meter. Ofgem’s guidance on storage at FIT installations says generation payments continue where the generation meter only measures the output of the FIT installation. Deemed export payments continue in the same cases.
The three routes that keep your payments
Ofgem sets out three ways to meet that test.
| Route | What it means | Can the battery charge from the grid? |
|---|---|---|
| Meter between panels and battery | The generation meter sits between the panels and the battery, so it only sees solar power | Yes |
| No grid charging | The battery is set so it can’t charge from the grid, with a signed declaration | No |
| Approved bi-directional meter | A meter that can tell the difference between flows is fitted, with a signed declaration | Yes |
Whichever route applies, the guidance says adding storage should be reported to your FIT licensee, the supplier that pays your tariff.
AC-coupled and DC-coupled batteries
An AC-coupled battery has its own inverter and connects to the household wiring, after the generation meter. The meter keeps counting only what the panels make, so this is usually the simplest way to add a battery to a FIT system. It also leaves your existing solar inverter in place.
A DC-coupled battery connects on the panels’ side, usually through a hybrid inverter that replaces the old one. Depending on where the generation meter ends up, the meter may see power coming out of the battery. It can still be done, but the design has to meet one of Ofgem’s routes, and that has to be checked before anything is ordered.
Before you get quotes
Find your FIT paperwork: the supplier you are paid by, your FIT ID and the details of the generation meter. Then ask each installer:
- Is the battery AC-coupled or DC-coupled, and where does it sit in relation to the generation meter?
- Will it charge from the grid? If so, which of Ofgem’s routes allows that?
- Will you help with the notification and any declaration to my FIT supplier?
If you bought the house with panels already on it, check that the FIT has been transferred to you first. Buying a house with solar panels explains how.
What it costs
The Energy Saving Trust puts home batteries at £1,500 to £10,000, with a 5 kWh system around £4,600. Adding a battery to existing solar panels explains how a battery is sized and fitted to a system that is already on the roof.
Bottom line
You can usually add a battery to a Feed-in Tariff system without losing your payments, as long as it is wired and set up so the generation meter only counts solar power, and you tell your FIT supplier. Ask any installer to explain which of Ofgem's routes their design follows. Our quotes are free. Call 0121 330 1151, 9am to 7pm, 7 days.