Questions to ask any solar installer

Most homeowners get three quotes for solar and compare them on price. That is the one number the quotes are designed to make easy to compare, and the least useful. The questions below tell you what you are actually buying. Ask each installer the same ones and write the answers down.

Will you come to the house before quoting?

A quote from a satellite image cannot see the chimney shadow at four in the afternoon, the state of your consumer unit, or where a cable can run without crossing your hallway. An installer who prices from a desk has to add margin for what they have not seen, or revise the price once someone turns up. A survey before the number means the number holds.

Have you looked at my bills?

A system sized to a standard package will be too big for some households and too small for others. The right size comes from how much you use and when. If someone is home in the day, panels alone do most of the work. If the house is empty until six, a battery is what moves your daytime power to when you need it. An installer who has not asked for 12 months of usage is guessing on your behalf.

Who will I deal with after I sign?

This is the question most people forget to ask and most regret not asking. Get a name. Ask whether that person will be the same from survey to handover, and whether they will still be reachable in a year. A call centre is an answer too, and a useful one to hear before you sign rather than after the scaffolding comes down.

Who does the installation, and who signs it off?

Many national firms sell the job and subcontract the fitting. You should know when that is happening. Ask who will be on your roof, who checks their work, and what their electrical qualifications are. A named engineer who signs off every job tells you more than a page of accreditation logos.

Is the price fixed, and what could change it?

Ask what happens if the roof needs extra work, the consumer unit needs replacing, or the scaffold stays up longer. A fixed price in writing, with the exclusions listed, protects you. A price that is "subject to survey" after you have signed is a starting point, and starting points move.

What happens if the system makes less than you forecast?

Every quote comes with a savings figure. Ask what the installer will do if the real figure is lower. Most will point to the weather. A better answer is a written forecast, a check against your real bills after a year, and a commitment to put it right if the shortfall is within their control.

What is covered, and by whom, if something fails in year eight?

Panels, inverter and battery each carry a manufacturer warranty. The installation itself carries a workmanship warranty from the installer. Ask whether the workmanship warranty is insurance-backed, which means it survives if the installer does not. Ask for all of it in writing before you pay a deposit.

Can I see installations you have done nearby?

Photos of real roofs in your area tell you two things: whether the installer has worked on houses like yours, and whether their work looks tidy from the street. Ask for addresses you can drive past, or for customers who are willing to speak to you.

What to do with the answers

Put the three quotes side by side and compare the answers as carefully as the totals. The cheapest quote is often the one that has left the most out. The right installer answers every question above without hesitation, and most of the answers are already in the written plan they give you.

We are happy to be asked all of them.