If you already have solar panels and no battery, the Warm Homes Loan Scheme can pay for adding one. The scheme rules list battery storage both on its own and paired with solar, with a loan cap of £15,000, and a battery quote can include connecting it to the panels you already have. This guide covers what the loan will and will not pay for, how the numbers work on a typical retrofit, and the order to do things in.
What the Warm Homes Loan Scheme is
The Warm Homes Loan Scheme is a UK-wide, lender-led scheme. Participating lenders offer loans for low-carbon home upgrades, and government funding is used to bring the interest rate down. The government factsheet of 27 October 2026 says some loans are interest-free, not all, and that the aim is rates up to 5 percentage points lower than regular loans, with terms of up to 30 years in some cases. Rates vary by lender.
It is a loan, not a grant. You borrow the money and pay it back, and the lender decides whether to lend after its own credit and affordability checks.
Does a battery on existing solar qualify?
Yes. The scheme rules (version 3, September 2026) list "electrical battery storage" as an eligible measure and say both standalone battery installations and those paired with solar PV qualify. They also say a battery quote may include integration with an existing PV system, monitoring apps and the isolators or protection devices the job needs.
The loan cap for a battery is £15,000. That covers the battery, the labour and the ancillary work needed to make it run properly.
What the loan will not pay for
The scheme can only finance the measures listed in its rules and the work needed to fit them. For an existing solar owner, that rules out a few common jobs:
- Repairs and servicing. Fixing a fault, cleaning panels or a service visit are not listed measures.
- A like-for-like inverter swap on its own. Replacing a failed inverter is not a listed measure by itself. If the inverter is near the end of its life, ask your installer how that work fits a battery or extra-panels quote.
- Roof repairs. The rules say the scheme will not fund replacement roofing or structural work needed before solar. Lenders may offer a separate, ordinary loan for this.
- An EV charger on its own. A charger only counts as part of a solar or battery installation, and it must be OZEV approved.
Adding more panels instead of, or as well as, a battery
The rules also list solar PV, including "the addition of solar panels to an existing installation", with its own £15,000 cap. If your roof has space and your system is small, extra panels plus a battery can be quoted together, as long as each part stays within its cap.
How the numbers work on a typical retrofit
Our published price for a Tesla Powerwall 3 battery retrofit is £7,400 to £8,400 fitted on existing solar, which sits well inside the £15,000 battery cap. Installing a battery in a home in Great Britain carries 0% VAT until 31 March 2027; from 1 April 2027 the rate goes to 5%. Fitting before that date keeps the VAT at 0%.
What you repay depends on the lender, the rate and the term you choose. Because some Warm Homes loans are interest-free and others are not, compare the total amount repayable on each offer, not just the monthly figure.
Who can apply
- Owner-occupiers and private landlords, borrowing personally, for a home in the UK.
- There is no income limit set by the scheme. Each lender runs its own checks and may ask for an Energy Performance Certificate.
- You need an MCS-certified installer for a battery or solar installation.
The order to do things in
- Get an MCS-certified installer to survey your home and give you an itemised quote for the battery or extra panels.
- Choose a lender from the GOV.UK list of participating lenders and apply to them directly with that quote.
- Once the lender approves the loan, book the installation.
Be wary of anyone who cold-calls offering a Warm Homes Loan or asks for a fee to apply. The government and lenders do not sell these loans by cold-calling.
Is a battery retrofit worth it?
That depends on how much of your solar you export now and the tariff you are on. Our guide on whether to add a battery to existing solar works through the decision. If you want to use the loan, our Warm Homes Loan Scheme page for Greater Manchester and Lancashire sets out what it covers and how we quote for it.
Solar Maintenance Solutions Limited is authorised and regulated by the Financial Conduct Authority (FRN 1048290). We are a credit broker, not a lender, and we do not arrange Warm Homes Loans: you apply to a lender on the GOV.UK list directly.