A solar quote is a list of promises, and every line on it should be specific enough to check. This guide goes through what each line should say, what is often left off, and the questions worth asking before you sign anything. If a word on the quote is new to you, the glossary explains it in one plain sentence.
The system: size, panels and output
Start with the headline number. System size is given in kWp, kilowatt peak: the array’s output in full sun. It should equal the number of panels multiplied by the rating of each one. On the example estimate for a semi-detached house in Exeter, 14 × 445 W panels make 6.2 kWp. If a quote’s sum doesn’t work the same way, ask why.
The panel line should name the make, the model and the count. “Premium panels” or “high-efficiency modules” gives you nothing to look up. A model number lets you look up the rating, the size of each panel and the warranty that comes with it, and it lets you compare two quotes like for like.
If a line can’t be checked, it isn’t finished.
Then the output. A quote should give the yearly generation it expects, in kWh, and say what that figure rests on: the pitch, the direction the roof faces and any shading. On the example estimate, 6.2 kWp on a 35° roof facing S–SW comes to about 5,400 kWh a year. That is an estimate, and a good quote labels it as one.
The inverter and the battery
The inverter turns the panels’ direct current into the alternating current your home runs on. The quote should give its make, its model and its type:
- one string inverter, where the roof is simple
- optimisers or micro-inverters, where the roof has shade or more than one face
It should be sized to the array. Never oversold.
If a battery is included, it needs lines of its own: the make, the model, the capacity in kWh, how it connects to the rest of the system, and where it will live, whether that’s a garage, a utility room or an outside wall. It should be priced separately, too, so you can see what it adds. On the example estimate, a 10 kWh battery adds £4,500. A quote that folds the battery into a single total has made that choice for you.
Mounting, scaffolding and the electrical work
Mounting means the rails and the fixings that hold them to the roof. They depend on your covering, because slate, tile and flat roofs are each fixed differently. The quote should say which mounting system is used, and whether the panels sit on top of the roof or are set into it.
Scaffolding should be a line of its own. Ask which sides of the house it covers, how long it stays up and, if it has to stand on a pavement or a neighbour’s ground, who arranges permission.
The electrical work deserves the closest reading. Look for:
- the cable route from the roof to the inverter
- the isolators that let each part of the system be switched off safely
- the consumer unit: the solar circuit needs its own place in your fuse box, and if yours needs work, that should be priced here
- earthing, and any change needed at the meter
- whether a generation meter, which counts what the roof makes, is included
Electrical work has to be notified under Building Regulations. In England and Wales that is Part P, and an electrician registered with NICEIC can self-certify the work. The quote should say who does it.
Certificates, notifications and warranties
Some paperwork comes before the install and some comes after. The quote should say who handles each piece.
- Planning. Most home solar is permitted development, but listed buildings, conservation areas and flats can need planning permission. Check first.
- The MCS certificate. The installer should be MCS-certified and the system registered once it is fitted, which is what makes it eligible for export payments under the Smart Export Guarantee.
- The DNO notification. Your local distribution network operator must be told about a grid-connected system. Small systems are usually notified after connection; larger ones usually need approval first.
Warranties come in layers, and each should be named:
- manufacturers’ warranties for the panels, the inverter and the battery, each covered by the company that made it; panels often carry one warranty for the product and another for its output over time
- the workmanship warranty, which is the installer’s promise for the fixings, the wiring and the work itself
- the insurance-backed guarantee, which keeps the workmanship warranty good if the installer stops trading
A line that says everything is covered, without saying who covers what, isn’t saying much.
Deposit, payment stages and what is left out
The quote should set out what you pay and when: the deposit, any stage payments and the final balance. Ask how the deposit is protected. It is reasonable for the last payment to fall due once the system is working and the paperwork is in your hands.
If the installer offers finance, it deserves the same reading as the quote: the rate, the term, any fee for paying early and what happens if you move.
Then the exclusions. They usually sit in the small print at the end, and they are where a price moves. Things that are often missing, or quietly excluded:
- work on the consumer unit, if it turns out to need it
- extra fixings, if the rafters need them
- scaffolding for a second side of the house
- bird protection around the array
- making good after cables are run through walls and ceilings
- a base or bracket for the battery
- the tariff and export rate behind any savings figure, which vary by supplier and should be written down
Questions worth asking before you sign
- Who will do the work: your own team, or a subcontractor?
- What could change the price between now and the install?
- Who notifies the DNO, and who registers the system with MCS?
- Which warranty covers what, and who do I call if something goes wrong?
- Is the insurance-backed guarantee included, and who provides it?
- How is the deposit protected, and when is the balance due?
- What unit price and export rate do the savings assume?
- What isn’t included?
What we do
We read every quote line by line and set it against what the same system costs elsewhere before it reaches you. If anything could move the price, you’ll know why before you sign. If the installer offers finance, that is a separate agreement: read it the same way, line by line. We don’t arrange or recommend finance. We never fit a panel, so we never need to sell you one.
