Commercial Solar Payback: How Long in the UK?

For a business or farm that uses most of its power in the day, commercial solar often pays for itself in around 4 to 8 years. After that, the power it makes is close to free for the rest of its 25 years or more.

But the range is wide, and one thing matters more than anything else: how much of the solar you use yourself.

What drives payback

How much you use on site. Businesses pay on average about 24.5p per kWh for grid electricity (government figures for April to June 2026), and smaller users pay more. Export usually earns far less. So every unit you use yourself is worth several times a unit you export.
The cost of the system. Bigger systems cost less per kW. Roof work, scaffolding and grid upgrades add cost.
Where you are. In the South West, a well-placed system makes around 1,050 kWh per kWp a year, compared with under 900 in Manchester.
Your electricity price. The more you pay for grid power, the faster solar pays back.
Tax. Capital allowances can bring forward some of the saving (see below).

A worked example

This is an illustration, not a quote. Every site is different.

A business near Exeter fits a 100kWp rooftop system.

Example cost: £90,000 (£900 per kWp).
Output: about 100,000 kWh a year (1,000 kWh per kWp, allowing for a real roof).
Grid price: 28.6p per kWh, the average for small business users.
Export price: 5p per kWh.

If the business uses 70% of the solar on site:

Savings: 70,000 kWh × 28.6p = about £20,000 a year
Export: 30,000 kWh × 5p = about £1,500 a year
Total: about £21,500 a year, so payback in around 4 years

If it uses only 40% on site:

Savings: 40,000 kWh × 28.6p = about £11,400
Export: 60,000 kWh × 5p = about £3,000
Total: about £14,400 a year, so payback in around 6 years

Same system, same roof. The difference is how well it matches the site’s use. That is why we design around your half-hourly data.

The example leaves out maintenance, inverter replacement and finance costs, and assumes today’s prices. Panels also lose a little output each year, usually well under 1%.

Tax and business rates

Capital allowances. Solar panels count as “special rate” assets. Full expensing doesn’t apply, but companies can claim a 50% first-year allowance, and the Annual Investment Allowance (up to £1 million) covers most plant and machinery. Ask your accountant how this applies to you.
Business rates in England. Rooftop solar and other on-site renewables are exempt from business rates until 31 March 2035.
Export income received by a business is taxable as a business receipt.

Ways to improve payback

Size the system to your use, not just the roof area.
East-west layouts spread output through the day.
Add a battery if you have an export limit or a time-of-use tariff.
Shop around for export rates. See getting paid for exported power.
No capital? A solar PPA can give you cheaper power with no upfront cost.

What we do

We look at your bills or half-hourly data, model the output for your roof and give you a clear payback figure for your site. Get a quote →

Sources

Facts last checked 8 October 2026. The worked example is illustrative only. This is general guidance, not financial or tax advice.

How long does commercial solar take to pay back?