1. Put the quotes on the same specification
The single biggest reason quotes look wildly different is that they are not for the same system. Before comparing prices, write down the panel count and total kWp, the inverter type and the battery capacity for each quote. If one installer has quoted 4kW and another 6kW, compare price per kWp rather than the totals.
2. Compare generation, not promised savings
Estimated annual generation in kWh can be checked against your roof orientation, pitch and shading. Savings in pounds depend on assumptions about your usage and future energy prices, which every installer sets differently. Ask what tariff and self-consumption percentage a savings figure assumes.
3. Read the exclusions before the price
Scaffolding, consumer unit upgrades, bird protection, roof repairs and long cable runs are the items most often left out of the cheapest quote and added after survey. A quote with a clear exclusions list is usually more trustworthy than one without.
4. Separate the three warranties
Panels, inverter and workmanship are covered by different warranties from different parties. Panel performance warranties commonly run 25 years, inverters 5–12 years, and workmanship anywhere from 2 to 10 years. The workmanship warranty is the one that depends on the installer still trading, so check how long the company has been established.
5. Verify the installer, not just the paperwork
Ask for the MCS certificate number and the company registration number, and confirm the trading name on the quote matches both. Every installer in our network has their company and MCS details checked before they can receive an enquiry, but you should still confirm directly.
6. Then negotiate on specification
If one quote is higher, ask what it includes that the others do not. Better inverters, longer workmanship cover and proper bird protection are worth paying for; a vague brand upgrade is not. For typical price ranges in your area, see our UK solar cost guide or your regional cost page.