For homeowners on certain benefits there is a low-income voucher that is worth up to £10,000 and that does not require any contribution from the homeowner.
If you want to install measures worth up to £10,000 you will not have to pay anything and the voucher will cover the whole amount.
If you want to install measures worth £11,000 the voucher will still only cover £10,000 and you will have to pay the remaining £1,000.
You will not need to pay a deposit if your measures cost within the £10,000 covered by the voucher.