Feasibility Studies

Most commercial solar schemes that fail do so for one of four reasons: the roof, the yield, the grid or the planning position. A feasibility study tests all four while changes are still cheap. Nobody has paid for detailed design yet, and no installer has been asked to price anything.

The roof comes first. A desktop review of aerial images, drawings and any energy certificate narrows the field. Then the structure needs a proper look on site. Rusted purlins, an old membrane or light sheeting can rule out a roof that looks perfect from the air. What the roof can carry, rather than its floor area, usually sets the size of the array.

Yield comes next, and it varies more than people expect. The European Commission's PVGIS tool puts one kilowatt-peak of south-facing panels, tilted at 35 degrees with 14% system losses, at about 1,080 kWh a year in Ipswich, 1,050 in Exeter and 810 in Inverness. Orientation, tilt and shade move those figures again. A flat roof with panels facing east and west gives less energy per kilowatt-peak but holds more panels. A study models your roof, not a national average.

Then the connection. Generators above the small-scale G98 limit of 16 amps per phase need a G99 application to the local network operator. Under G99, a generator below 1 MW is Type A and one from 1 MW up to 10 MW is Type B. The operator may find that the network needs reinforcing, and that cost can land on the project. Ofgem's December 2025 update on its connections review proposed penalties for operators that miss deadlines. It tells you where the delays sit: waiting for an offer is the part of a project you control least.

Consents come last. Many rooftop schemes need little beyond building control sign-off, but a listed building or a conservation area changes that, and a ground-mounted array is a planning application in its own right. The rules differ between England, Scotland and Wales, so we check the one that applies to your site.

Above 50 kWp the MCS installer standard, MIS 3002, no longer applies, because its scope stops at 50 kWp of DC output. So the specification that follows a study must name its own design, testing and commissioning standards.

The study ends with a go or no-go. A no-go is still a useful result. You have paid for a few days of advice instead of a design fee and a tender. A go comes with the capacity, a cost range and the main risks written down, so every installer prices the same brief.