| Estimate required before the contract | MCS performance estimate, in writing |
|---|---|
| Workmanship guarantee under the Consumer Code | At least 2 years, insurance-backed |
| Maximum deposit under the Consumer Code | 25 per cent |
How to use this list
Copy the questions that apply to your quote into an email or message. Send the same ones to each shortlisted installer. Then file the replies next to the quotes, because you will want them later.
The questions fall into five groups: calculation, certification, delivery, aftercare and payment. Each comes with a reason, so you know what a good answer looks like. If you have not yet built your comparison table, start with our like-for-like method.
Be polite and specific. A good installer will welcome the detail, because it shows you are serious. A poor one may dodge, yet that tells you something too.
Calculation questions
These questions test the forecast behind the savings figure. A forecast is only as good as its inputs, so test them.
- Can you send the MCS performance estimate for my roof? The MCS standard requires a written estimate of annual generation before the contract is awarded. It must carry a note that the figure is guidance, not a guarantee.
- What orientation, tilt and shading did you assume? The estimate table lists these. If the site was assessed remotely, the estimate must say the values were estimated and that actual output may differ.
- What electricity use and occupancy did you assume for self-use? The self-consumption figure depends on them. Compare it with your real bills.
- What energy prices and export rate did you use for savings? The Consumer Code says assumptions must be set out and attributed to a reputable source. Savings should reflect your actual energy use.
- If you use other software, how does it compare with the MCS estimate? Other estimates must not be more prominent than the MCS one. A warning is needed if they look significantly better.
To judge the size of the system itself, see how many solar panels you need.
Certification questions
These questions confirm who the firm is and what standards it follows, since a name alone proves nothing.
- What is your MCS certification number, and which body certifies you? The Consumer Code requires members to disclose their MCS status and certification body before you sign.
- Are you also a member of a consumer code, and which one? MCS covers the install. A consumer code covers selling, contracts and complaints. Ask for both.
- Is the contract in the name of the same business that holds both? The Code says the contract should not be in the name of more than one business.
- Will you give me the registered company number and VAT number? The Code lists these as pre-contract information.
You can also check the answers yourself. Our guide to checking a solar installer explains how.
Delivery questions
These questions cover who does the work and what could change the price, because these answers decide what the final bill covers.
- Who surveys, designs, installs and commissions the system? The Code requires you to be told the name of any subcontractor and what they will do. The MCS contractor stays responsible.
- Will a technical site survey happen before I sign? The Code says installers should carry out, and pay for, a survey if possible. Without one, your estimate may change.
- Which approvals does my job need, and who handles them? The installer must tell you about approvals in writing, including planning, building regulations and network notifications. Read our guide to planning permission for solar panels.
- Will you apply to the network operator, and under which process? The MCS contractor must notify the operator under G98 or G99. See G98 and G99 explained.
- What site conditions could add cost, and at what rates? The Code expects quotes to list these. For example, scaffolding or roof repairs may be extra.
- What are the start and completion dates? The contract should include a timetable.
Aftercare questions
These questions cover what happens once the panels are on the roof, which is when you rely on the firm’s promises.
- Which warranties apply, and who provides each? Ask for the product, performance and workmanship terms separately. Our guide to warranties and certificates explains the differences.
- How long is the workmanship guarantee, and is it insurance-backed? The Code requires at least 2 years, transferable, and backed by insurance if the firm stops trading.
- Who pays for access if a panel must be replaced? Check whether the warranty covers labour and access, not just parts.
- Which papers will I receive at handover? The MCS standard lists a document pack and a signed declaration. An MCS certificate follows within 10 working days of commissioning.
- How do I report a fault, and what response time do you promise? The Code requires a way to contact the firm after the job.
- Will the work affect my home insurance? Ask what the insurer needs. See solar panels and home insurance.
Payment questions
These questions protect your money, because early payments carry the most risk. Our guide to deposit and payment checks explains the rules in detail.
- How much is the deposit, and what is it for? The Code says a deposit should not exceed 25 per cent under any circumstances.
- How are deposits and stage payments protected if you stop trading? Code members must insure them. Ask for the certificate.
- What are the payment milestones? Deposit and advance payments together cannot exceed 60 per cent.
- What is the cancellation process? The Code requires at least 14 days to cancel without penalty, with a prominent form.
- If I use finance, what is the total payable? Payback figures must count the repayments and interest.
Spotting a weak answer
Some replies should worry you. Vague wording, pressure to sign quickly and refusal to put things in writing are all signs. Our list of solar quote red flags covers the rest.
Also compare answers across installers, because patterns show up quickly. If one firm promises far more output than the others, ask why. The cause may be a different assumption rather than a better system.
Local factors can shape the answers, so read our pages on quotes in London and what homeowners in the East of England can expect.
What to do with the replies
Once the answers arrive, add them to your comparison table. Do not rush. Remove any installer who will not answer. Then choose between the rest on scope, forecast, price and protections.
If you want a wider field, you can request quotes from MCS-certified installers. Solar Panel Price Check is independent and is not an installer.