How to compare solar panel quotes in the UK
Understand the assumptions, design, equipment and contract terms behind a UK solar proposal, beyond its headline price.
Reviewed 2026-09-24 ยท 6 min read
Start with the same question
Two quotes are comparable only when they describe the same property, demand and scope. Ask each installer to state the array size in kWp, module model and count, inverter model, battery usable capacity and power, mounting system, monitoring, commissioning and aftercare. Record whether scaffolding, access equipment, DNO administration and making good are included.
A low price can reflect a smaller system, a different roof layout or omitted work. Ask for a line-by-line specification and an explanation of every optional item. Do not compare a firm design with an early budget estimate as though they were equivalent.
- Panel dimensions, efficiency and product/performance warranty
- Inverter warranty, monitoring and replacement route
- Battery usable kWh, charge/discharge kW and warranty conditions
- Scaffolding, roof repairs, certification and commissioning
Test the generation assumptions
Generation is an estimate, not a guarantee. Ask what software and weather dataset were used and whether orientation, pitch, shading, temperature and system losses were included. Ideally the estimate identifies monthly as well as annual output. Compare like with like: a perfect-orientation estimate should not be set against a shade-adjusted model without explaining the difference.
Savings depend on when electricity is generated and used, export arrangements, import prices, battery operation and future consumption. Request self-consumption and export separately, with lower and higher scenarios. A payback period is a scenario, not a promise.
Ask whether the generation figure is before or after system losses, and whether the battery has been included in the calculation. A panel rating is measured under standard test conditions and is not the same as annual energy delivered at your property. Shading, inverter clipping, temperature and downtime can all affect the result.
If an installer uses a financial model, request the inputs as a separate schedule. Record the assumed import price, export value, annual degradation, battery efficiency, maintenance and system life. This makes it possible to update one assumption without accepting a black-box payback figure.
Read the contract
Check deposits, cancellation, delivery, variations, roof repairs, DNO delay, ownership and complaints. Identify the legal contracting party and distinguish workmanship remedies from manufacturer warranties. Verify claimed certification directly and keep the documents promised before deciding.
Look for an installation programme that explains what happens if a survey changes the design. Confirm whether the price is fixed and what counts as a chargeable variation. Ask who removes packaging, makes good penetrations and leaves the monitoring account in your name.
A warranty is only useful if you know who administers it and how a claim is made. Ask whether labour, shipping and access costs are covered, and whether a manufacturer warranty depends on registration or an approved installer. Keep the final as-built specification, certificates and serial numbers.
Common questions
Is the cheapest solar quote best?
Not necessarily. Compare complete specification, predicted output, included work, warranties, contract and aftercare.
Should every quote predict the same generation?
No. Roof, equipment and modelling differ; the key is transparent, comparable assumptions.
What should be in a quote?
Design, models, estimate, price and inclusions, warranties, programme, payment terms, approvals and aftercare.