Three solar quotes for the same roof will not agree, and the reason is almost never the panels. They will assume different generation, different self consumption, different scaffolding, different warranty terms and sometimes a different system size. Comparing them is a matter of forcing all three onto the same basis first, which takes about an hour and changes the answer surprisingly often.
What a real quote has to state
System size in kilowatts peak, the number and rating of the panels, the inverter make and model, the modelled annual generation with the assumptions behind it, the assumed self consumption fraction, scaffolding and access, making good, the warranty periods for panels, inverters and workmanship separately, who registers those warranties, the total price with VAT treatment stated, and the payment schedule. A document without those lines is a price, and two prices cannot be compared.
Why a solar panel online quote is only a starting point
A desktop or online quote is generated from a postcode, a roof outline and an assumed orientation. It cannot see the shading from the neighbour's chimney, the condition of the covering, the route from roof to consumer unit, the state of the board or whether the scaffold can stand anywhere useful. Those are the things that move a price. Use an online figure to decide whether to proceed, never to decide between contractors.
Normalise the three quotes before you read them
Put them on one sheet: same system size where possible, generation assumptions written out, self consumption assumption stated, scaffolding in or out, making good in or out, warranty lengths in three separate columns, and the deposit and stage payments. Most of the apparent price gap disappears at this point, and what remains is usually specification or programme. If one quote models much higher generation than the other two on the same roof, it is the assumption that is different, not the roof.
The parts of a quote that are about risk, not price
A large deposit, a long lead time with money up front, a warranty held by a company with no trading history, and a guaranteed savings figure with no stated assumptions are all risk rather than value. So is a quote that arrives without anybody visiting the property. Check the company at Companies House, check the certification scope, and treat a pressured discount that expires today as what it is.
Questions people ask about solar panel quotes
How many solar quotes should I get?
Three is the usual sensible number: enough to see the spread of assumptions, few enough to compare properly. All three should be from firms that have visited or surveyed the property, because a desktop price is not a quote.
Why are solar quotes so different for the same roof?
Because they are modelling different things. Different assumed generation, different self consumption, different inclusion of scaffolding and making good, and sometimes a different system size. Normalise all of that and the gap narrows sharply.
Should I pay a deposit?
A modest deposit is normal. A large one is a risk you are taking on the company's solvency, and it should be protected under the consumer code the firm belongs to. Check what that protection actually covers before paying.
Does a quote need a solar panel survey on site?
For anything you intend to buy, yes. Shading, roof condition, the cable route and the board are what move the price, and none of them is visible from an aerial image.