Twelve questions to ask before you sign — covering MCS certification, sub-contracting, DNO sign-off, finance and warranty traps.
Why this checklist exists
MCS certification is necessary, not sufficient. There are 2,400+ MCS-certified solar installers in the UK and the quality range between them is enormous — from family-run firms with 20-year track records to companies that subcontract every install to whoever's cheapest that week.
These are the twelve questions we'd ask before handing over a deposit. None of them are confrontational; any reputable installer should be able to answer all twelve in a five-minute conversation.
The 12 questions
Run through these in order. Walk away if you get vague answers on certification, sub-contracting or DNO sign-off.
1. What's your MCS certificate number? (Verify it on mcscertified.com — takes 30 seconds.)
2. Are you also RECC or HIES registered? (Required for finance via most reputable lenders.)
3. Will the team on my roof be your direct employees, or sub-contracted? (Sub-contracting isn't disqualifying but ask why and how the warranty handles it.)
4. Who handles the DNO G99/G98 application — you or me? (It should be them.)
5. What's your scaffolding sub? (Same firm every time = better safety record.)
6. What's the workmanship warranty length, and what does it specifically exclude?
7. Who services the panels and inverter if your company stops trading? (MCS Foundation steps in but you want clarity.)
8. What's the panel manufacturer's UK warranty agent? (Not all panel makers have one — that matters for claims.)
9. Is the inverter warranty parts-only or parts-and-labour?
10. What's your no-show / delay clause? (Useful when the install slips by 6 weeks.)
11. Can I see two reference installs within 5 miles, completed in the last 6 months?
12. What's your written quote validity period, and is the price fixed or subject to change?
Red flags
If any of the following appear, walk away. There are too many good installers to tolerate any of them.
Pressure to sign 'today' for a 'special discount'.
Cash-only deposits or deposits over 25% of the contract value.
Refusal to commit to a written installation date in the contract.
Quote materially below comparable quotes — especially if labour rate is unrealistically low.
'Free solar' or PV lease arrangements where the panels stay owned by the installer.
Frequently asked questions
How do I verify an MCS certificate?
Visit mcscertified.com, search by company name or MCS number, and check that the certificate is current (not lapsed) and covers the technology being installed (Solar PV in this case).
What's the difference between MCS, RECC and HIES?
MCS certifies the technical install. RECC (Renewable Energy Consumer Code) and HIES (Home Insulation & Energy Systems) are consumer codes that cover deposit protection, complaints handling and finance regulation. Look for an installer registered with at least one consumer code.