Commercial Solar

Two claims turn up constantly in commercial solar proposals, and both are wrong. Correcting them changes the numbers your finance director signs off.

Solar does not qualify for full expensing. Full expensing applies to main-pool plant and machinery. Solar PV is classified as special-rate expenditure, and cannot claim full expensing. The route that does apply is the Annual Investment Allowance — 100% relief in year one up to the £1m annual limit — with the 50% first-year allowance for special-rate assets above it. For most single-site commercial rooftops the AIA covers the whole project and the cash effect is the same, but the claim has to be made correctly.

On-site generation plant stays outside your rateable value to 2035. Installing rooftop solar does not increase your business rates during that period. Worth stating plainly, because the opposite assumption stops projects that should proceed.

Grid connection is the real constraint, not the roof. The simpler G98 notification route is capped at 16 A per phase — roughly 3.68 kW on a single phase — so effectively every commercial system needs a G99 application to the network operator before work starts. That process, not the installation, usually sets your timeline, and on constrained parts of the network it can cap your permitted export. We run the G99 application as part of the project rather than leaving it to the end, and where export is limited we design for self-consumption and storage instead of pretending the constraint is not there.

The economics follow self-consumption. A unit used on site displaces your full delivered price, including the non-commodity charges that make up much of a commercial bill. A unit exported earns the Smart Export Guarantee rate, which is far lower. An honest commercial design starts from your half-hourly load profile, not from how many panels the roof will take.