Check the usable half of the roof
Agree the scaffold footprint, cable route and any shared access before pricing. A side extension or dormer may change which roof positions are useful, even where the main roof looks straightforward.
Build a roof and access record
A detached property can have several promising roof faces, but ask for a separate yield and installation explanation for each. Combining a clear main roof with an awkward garage roof can add work without proportionate useful generation. Review the roof checks.
Use measured electricity demand
Large floor area can coexist with modest electricity use where heating is gas and the home is empty by day. Conversely, an EV or heat pump changes the load. Separate current measured use from future scenarios. Estimate the bill reduction.
Ask for a complete proposal
The cash price should identify modules, inverter, mounting, access, electrical work and commissioning. Keep optional storage and backup separate so their additional return is visible. Read the installation scope and check a received quote.
Use a surveyed annual generation estimate for the actual layout, rather than treating a property-type example as a forecast. The payback model accepts that explicit generation and keeps bill reduction separate from exports.
Sources and review dates
Research-based guidance. Source checks do not imply product testing or verification of an individual installer.
- Energy Saving Trust: Solar panels. Solar suitability, generation, roof and installation considerations; not a local quote dataset. Scope: UK. Checked .
- Trinasolar: Vertex S+ NEG9RC.27. Example 450 W module format 1762 x 1134 x 30 mm; identify exact module revision on a quote. Scope: Product specification. Checked .
Registry sources-2026-11-01. Tariffs have a 30-day internal review interval. Methodology and assumptions.