Capital allowances
For UK businesses paying corporation tax, capital allowances are typically the biggest single funding lever on a commercial solar install.
Under the current corporation tax regime, the main rate is 25% on profits above £250,000. Plant and machinery investment (including commercial solar PV, battery storage, EV chargers and heat pumps) qualifies for capital allowances at the 25% main rate.
For most installs this means the business can offset 25% of the full install cost against corporation tax, often in year one of the install. On a 250 kW commercial solar install at £125,000, the corporation tax relief is around £31,250 in year one if Annual Investment Allowance (AIA) applies.
AIA (Annual Investment Allowance) lets businesses claim a significant first-year deduction (currently 50% on plant and machinery, with the remaining 50% written down over subsequent years) up to £1 million per year. Most residential-scale to mid-scale commercial solar installs sit within AIA, meaning the customer claims the full install cost against year-one profits.
For installs above £1 million in a single tax year, the remainder of the cost is written down through standard capital allowances over multiple years.
We model capital allowance treatment for every commercial install at proposal stage so the customer can see the post-tax cost figure alongside the headline figure.