The useful starting point
Use a public cost reference to orient yourself, then compare surveyed proposals. The same panel count can hide different access work, inverter choices and predicted output.
A useful cost reference
Energy Saving Trust guidance currently gives around £7,600 for a typical 4.5 kWp domestic solar system. This is a published broad estimate, not a Home Energy Compare market average or an offer for your address.
Roof access, the type of installation and work needed on the roof can affect the price. A quote should make clear whether storage is included. Do not compare a solar-only estimate with a solar-plus-battery package as if they cover the same work.
Ask for a complete scope
| Part of the proposal | What you need in writing |
|---|---|
| Panels | Manufacturer, exact model, number and total rated kWp |
| Roof layout | Placement, orientation, shading and access arrangements |
| Inverter | Model, output, monitoring and any future-storage compatibility |
| Installation | Scaffolding, mounting, cable routes and electrical changes |
| Connection | Responsibility for network approval or notification and any export limit |
| Handover | Commissioning records, certificates, warranties and support details |
Keep any exclusions beside the headline price. Unexpected consumer-unit work or a separate scaffolding bill can matter more than a small difference in panel cost.
Compare output as well as equipment
Two proposals with the same peak capacity may predict different annual generation. Ask each installer to explain the assumptions about orientation, shading and losses. A quoted annual kWh figure should be specific to the proposed layout.
The part of that generation you use directly avoids import purchases. Exported energy earns the rate available under your export arrangement. These values are not interchangeable, and household demand limits how much solar you can use at the moment it is generated.
Try a transparent worked example
Suppose a fictional system costs £7,000 and generates 3,400 kWh a year. If you use 40% directly, 1,360 kWh avoids import and 2,040 kWh is exported. At example rates of 27p import and 12p export, the first-year energy value is about £612.
Simple payback is then roughly 11.4 years. That calculation excludes maintenance, finance, degradation, equipment replacement and rate changes. It is not a prediction for a particular home. Change all of the inputs in the solar scenario tool.
Before you sign
Check the full cash price, payment stages, cancellation terms and the party responsible for workmanship. Verify any certification or consumer-code claims with the relevant organisation. If the roof is likely to need repairs, discuss whether it is sensible to complete them first.
Then use our installation process guide to understand the journey from survey to handover, and the panel comparison guide to examine the proposed hardware.
Published information supports your research. Your installer should confirm the exact product, suitability, scope and terms for your property.
Suggest a correction ↗Your next useful step
Put the information to work.
Take the questions that matter to your project, explore the numbers and decide what to ask next.