Russell Andrews
A solar and battery quote is a big document for a big decision, and the headline figure only tells part of the story. Two quotes can look alike on the first page and describe quite different systems underneath. This guide sets out what a good solar and battery quote should show, so you can judge any quote you hold, ours included, with confidence.
REST UK is MCS certified and HIES protected, and every point below is something you are welcome to put to us. If you already have a quote from another installer, send it over. We will review it alongside the design we would recommend for your home and, where we can match or improve on it, we will tell you, subject to assessment and approval.
Start with the system, not the total
A good quote names the equipment. Look for the panel make and model, the number of panels, the total system size in kilowatts peak (kWp), the inverter make and model, and the battery make, model and capacity in kilowatt hours (kWh). If a quote says "premium panels" or "branded battery" without naming them, ask which ones. You cannot compare warranties, performance or reputation for a product you cannot identify.
Check how the battery is described. Some quotes give the nominal capacity and others the usable capacity, and the two can differ. Ask for the usable figure, along with the maximum charge and discharge power in kilowatts. Our home battery size guide explains why both numbers matter.
Check the design is specific to your roof
A quote should reflect your property, not a standard package. Ask whether the installer has looked at your roof, either in person or through detailed survey data. The quote should show how many panels go on each roof face, their orientation, and any allowance for shading from trees, chimneys or neighbouring buildings.
Ask what happens if scaffolding, roof repairs or an electrical upgrade turn out to be needed. A design that overlooks shading or an ageing consumer unit can lead to extra work later, so it is better to find out now.
Compare what is included
Quotes are hard to judge when one bundles items another leaves out. Use this checklist and mark each quote yes, no or unclear:
- Scaffolding or access equipment.
- Any consumer unit (fuse box) upgrade or other electrical work.
- Smart meter or export meter requirements.
- Notification to the network operator and the MCS certificate.
- A monitoring app, and who sets it up with you.
- Removal of waste and making good after the installation.
- VAT, and whether the quote states the rate being applied.
Anything marked "unclear" is a question for the installer before you decide. VAT on installations is changing, so our guide to the solar VAT deadline is worth reading alongside your quotes.
Look at the protection behind the quote
Compare the guarantees as carefully as the equipment. For your solar and battery quote, note the product warranty on the panels, the inverter and the battery, how long each lasts, and whether labour is covered. Then look at the installation itself: is there a workmanship guarantee, who stands behind it, and what happens if the installer stops trading?
Check that the installer is MCS certified and whether the work is covered by a consumer code. Our guide to questions to ask a solar installer goes through these in more detail, and the HIES protection scheme page explains what that route covers.
Understand how the figures were worked out
Many quotes include estimates of how much electricity the system will generate and how much of it you will use. Treat these as estimates and not as promises. Ask what sits behind them: your annual electricity use, the roof orientation and pitch, the shading allowance, and the electricity price used.
If a quote includes a figure for bills or payback, ask to see how it was calculated and whether anyone independent has checked the method. The solar panel payback guide explains why these figures vary so much from one home to the next.
Also ask how exported electricity will be paid for. The Smart Export Guarantee pays you for surplus electricity you send to the grid, but rates differ between suppliers, so a quote should say which one it assumes.
Check the payment terms
Look at how much is due before work starts and when the rest is payable, and whether each stage is tied to a point in the installation. If you are using finance, make sure you understand who the lender is, the total amount repayable and any early repayment terms. Our flexible solar finance page sets out how REST arranges finance.
MoneyHelper explains that paying by credit card can give you extra protection under Section 75 of the Consumer Credit Act for purchases priced between £100 and £30,000. Whether it applies to a given payment depends on the detail, so check with your card provider. For the wider picture of what influences the price of a system, see our solar panel cost guide.
A simple way to check any quote
Put the quote in a table, or two side by side if you have more than one. Down the side, list the panels, system size, inverter, battery and usable capacity, what is included, product warranties, workmanship guarantee, accreditations, payment terms and the assumptions behind any savings figures.
Fill in what each quote says, then go back to the installer about every gap. A good installer will answer each one clearly and in writing. Our team is happy to do exactly that, so request a free quote and put your questions to us. If you are holding another quote, include it and we will take a look.
Estimates of generation and use depend on your property and habits and are not guaranteed. Finance is subject to status. REST UK acts as a credit broker, not a lender. This guide is general information and is not financial advice.