For a domestic UK solar installation, 10–25% is the standard deposit range. Above that, look for explicit deposit protection. 100% upfront is a walk-away signal.
What's a normal deposit?
| Deposit level | Assessment |
|---|---|
| 10% | Standard and conservative — common for smaller installers with good cash flow |
| 20–25% | Acceptable — covers material costs for a typical domestic system |
| 30–33% | Upper end of normal — acceptable if deposit is protected under HIES/RECC |
| 50%+ | Unusual — ask for written justification and confirm protection scheme |
| 100% upfront | Red flag — walk away unless there is a very specific, documented reason |
RECC and HIES both specify maximum advance payment levels, with deposit protection required above certain amounts. Check which scheme your installer belongs to.
What deposit protection means
HIES membership provides deposit protection of up to £2,000 per installation. If your installer becomes insolvent before completing the work, you can recover your deposit through the scheme. RECC offers equivalent protection. An installer who is a member of neither provides no formal deposit protection — your money is at risk in the event of company failure.
Alliant is a HIES member
What happens to your deposit
- Purchasing panels, inverter and battery in advance (manufacturer lead times are real)
- Covering scaffolding hire
- Part-funding ongoing business overheads
A legitimate installer will be happy to explain. If the deposit seems disproportionate to obvious materials cost, ask the question directly.
Stage payments vs single deposit
Commercial installations often use staged payments — typically 25% on signing, 50% on delivery of materials to site, 25% on completion. For domestic installs, a two-stage payment (deposit + balance on completion) is more common and equally acceptable.
A quote with deposit terms clearly explained
HIES-protected, written upfront, no surprises.
The balance payment
The balance is normally due on completion — after the system is commissioned and tested. 'Completion' means the system is generating, the monitoring app is set up, and the MCS certificate has been issued or confirmed as imminent.
Never pay the balance early
If you're funding via personal loan or green mortgage, coordinate so you're not personally bridging between deposit paid and finance drawdown.
Frequently asked questions
Can I negotiate the deposit amount?
Yes — installers will sometimes accept a lower deposit from well-researched, committed customers. A smaller deposit is lower risk for you.
What if an installer asks for a deposit before providing a written contract?
Don't pay. A written contract specifying system, price, payment terms, warranty and cancellation rights should be in place before any money changes hands.
Is a deposit receipt enough, or do I need a formal contract?
A receipt is not a contract. You need a formal written agreement specifying all terms before you pay. The receipt records payment; the contract protects you.
