The investment, tax relief, payback period and 25-year financial case
Commercial solar pricing in the UK varies by building type, roof complexity, system size and location. For a fully accredited MCS-certified installation using Tier 1 components in the South East, current market pricing runs as follows:
| Building type | Price per kWp (ex-VAT) | 50 kWp net price |
|---|---|---|
| Industrial / portal frame | £875/kWp | £43,750 |
| Office / commercial unit | £1,014/kWp | £50,700 |
| Retail / flat membrane | £921/kWp | £46,050 |
| Warehouse / logistics | £829/kWp | £41,450 |
A commercial solar installation qualifies as a capital asset and is eligible for the Annual Investment Allowance (AIA) under UK tax legislation. The AIA allows businesses to deduct the full cost of qualifying plant and machinery from their taxable profits in the year of purchase, at the current corporation tax rate of 25%.
This is not a reduction in the purchase price — it is a reduction in your corporation tax bill. The effect is the same: the net cost of the installation is reduced by 25% in year one, provided your business has sufficient taxable profit to absorb the deduction.
| Item | Industrial example (50 kWp) |
|---|---|
| Net installation cost (ex-VAT) | £43,750 |
| VAT (reclaimable) | £8,750 |
| Annual Investment Allowance (25%) | −£10,938 |
| Effective net cost after tax relief | £32,812 |
| Annual financial benefit (50 kWp, Kent) | £10,604/yr |
| Simple payback on effective net cost | ~3.1 years |
Payback period depends on the effective net cost after tax relief, the annual financial benefit, and any operating costs. For a well-matched commercial installation in the South East:
These ranges assume the 25% AIA is fully utilised in year one. Systems where self-consumption is lower — because the business operates primarily outside daylight hours, for example — will have longer paybacks. A site survey and consumption analysis gives a precise figure for your premises.
Beyond payback, the long-term financial case is driven by electricity price inflation. UK commercial electricity prices have risen significantly over the past decade. Even at a conservative 3% annual increase — well below the historical average — the value of the electricity a 50 kWp system generates over 25 years grows substantially:
| Electricity price growth | 25-year generation value (50 kWp) |
|---|---|
| Flat (0% per year) | £263,000 |
| +3% per year (conservative) | £355,000 |
| +5% per year (moderate) | £445,000 |
| +7% per year (historical average) | £562,000 |
Commercial solar has very low ongoing costs compared to most capital assets:
Enter your postcode and building type for a personalised savings estimate — system size, annual saving, payback period and 25-year projection.