Commercial Solar Payback Period: How Long Until It Pays Back?

For a typical UK business buying a system outright in 2026, simple payback usually falls between three and six years. Simple payback is the installed cost divided by the value of the energy savings and export income in a year.

Where a business sits in that range depends on a handful of factors:

• Self-consumption: the share of generation used on site rather than exported
• Import price: what the business currently pays per kWh for grid electricity
• Installed cost per kWp: driven by system size, roof type and access
• Location and orientation: how much the system generates per kWp
• Tax treatment: whether capital allowances reduce the effective cost

A panel lifespan of 25 to 30 years means payback is only the start of the return. A system that pays back in four years and lasts 25 can deliver more than five times its cost in avoided electricity over its life, even allowing for gradual degradation and an inverter replacement along the way.

The basic calculation is straightforward:

1. Work out annual generation: system size in kWp multiplied by the expected yield in kWh per kWp.
2. Split that generation into electricity used on site and electricity exported.
3. Value the on-site share at your import price, because each unit replaces one you would otherwise buy.
4. Value the exported share at your export tariff rate.
5. Add the two together for the annual benefit, then divide the installed cost by it.

A more complete model also deducts annual maintenance and insurance, allows for panel degradation of around 0.4% to 0.5% a year, includes an inverter replacement part-way through the system's life, and applies any tax relief to the upfront cost.

Many installer models also assume electricity prices rise every year. That shortens the projected payback, sometimes significantly. Inflation assumptions are reasonable to include, but ask for a version with flat prices as well, so the decision does not rest on a forecast nobody can guarantee. If a project only works with steep annual price rises built in, it is a weaker case than it looks on paper.

This is the point most solar sales conversations skip. A unit of solar electricity used in your building is worth what you would have paid for it from the grid, typically 24p to 29p per kWh for a UK business in 2026. The same unit exported is worth only the export tariff, which for commercial generators is often in single-digit pence.

Take a 100kWp system costing £90,000 that generates 95,000 kWh a year, with grid power at 25p and exports paid at 5p:

• 90% used on site: 85,500 kWh saves £21,375, plus £475 export income. Annual benefit £21,850, payback about 4.1 years.
• 50% used on site: 47,500 kWh saves £11,875, plus £2,375 export income. Annual benefit £14,250, payback about 6.3 years.

Now compare a cheaper installation, 10% less at £81,000, on the low self-consumption site. Its payback is about 5.7 years, still far worse than the dearer system on the high self-consumption site. Shaving the purchase price helps, but matching the system to your demand helps much more.

The higher your current unit rate, the faster solar pays back, because each kWh you generate and use replaces a more expensive one. Government figures put the average non-domestic electricity price at about 24p per kWh in the first quarter of 2026, but the spread between business sizes is wide. Smaller businesses typically pay around 28p to 29p, while the very largest users pay considerably less.

That has a practical consequence. A small business on a high unit rate can see a shorter payback from a modest system than a large industrial user with a heavily negotiated contract, even though the larger site buys its solar more cheaply per kWp.

Use your actual contract rate in any payback calculation, including the Climate Change Levy and any non-commodity charges that vary with consumption, but excluding the standing charge, which solar does not reduce. If your contract is due for renewal, ask installers to model a range of future prices rather than a single figure. It is also worth checking whether a time-of-use tariff, with higher daytime rates, would increase the value of your solar output.

Tax treatment can shorten payback considerably for profitable businesses that buy their system outright or through asset finance.

Solar panels are special-rate plant and machinery. The Annual Investment Allowance lets most businesses deduct qualifying spend of up to £1 million from taxable profits in the year of purchase. For a company paying corporation tax at the 25% main rate, a £90,000 system could reduce that year's tax bill by up to £22,500, bringing the effective cost down to around £67,500. On the high self-consumption example above, that would cut payback from about 4.1 years to roughly 3.1.

In England, eligible rooftop solar and on-site battery storage are also exempt from business rates until 31 March 2035, so the system should not add to your rateable value during its highest-value years.

Under a lease or power purchase agreement, the funder typically owns the equipment and claims the allowances instead. The right treatment depends on your business structure and how the system is owned, so confirm it with your accountant before building it into a business case.

The same system generates different amounts in different parts of the UK. Typical yields range from around 850 kWh per kWp a year in Scotland to about 1,000 to 1,100 kWh per kWp in southern England. On the 100kWp example, that is the difference between roughly 85,000 and 105,000 kWh a year, which moves payback by about a year.

Orientation matters too. South-facing pitched roofs give the highest yield per kWp. East-west layouts, common on flat and low-pitch commercial roofs, produce less per panel but spread generation across the morning and afternoon, which can raise self-consumption for businesses with steady daytime demand. On some sites that more than makes up for the lower yield.

Roof type affects the cost side of the equation. Metal roofs are usually the cheapest to work on, while fragile fibre cement roofs or flat roofs needing ballast add cost and lengthen payback. You can see how output varies by area on our solar panels by area pages.

A battery raises self-consumption by storing midday surplus for use later, but it also adds cost. Commercial storage typically costs around £400 to £700 per kWh of installed capacity for systems of 50 to 500 kWh, so whether it helps depends on how much surplus you would otherwise export.

For a business that already uses 85% or more of its solar output during working hours, a battery has little surplus to store and usually lengthens the overall payback. For a site that exports a large share of its summer generation, such as a warehouse with low daytime demand or a business that trades into the evening, a battery can shift enough energy to justify its cost.

Batteries can also earn value by charging from the grid at cheap overnight rates and discharging during expensive peak periods, if your tariff has a large enough price difference between the two. That income is separate from the solar case and should be modelled separately.

Ask installers to show payback for solar alone and for solar with storage, using your own half-hourly data, so you can see the battery's contribution clearly.

Different types of business use electricity in very different patterns, and that pattern largely decides self-consumption:

• Offices: high weekday demand that matches the solar curve well, but little use at weekends.
• Manufacturing: strong weekday baseload from machinery, often the best match of all if production runs during daylight hours. Weekend generation may be wasted unless shifts or storage use it.
• Chilled and frozen storage: refrigeration load peaks on hot sunny days, exactly when solar output peaks.
• Ambient warehouses: large roofs but low daytime demand, so systems sized to fill the roof tend to export heavily.
• Retail and hospitality: seven-day trading helps, but evening demand may need storage to capture.
• Schools: the summer holiday falls in the peak generation months, when buildings are largely empty.

Knowing which pattern fits your site is the quickest way to judge whether a quote's self-consumption figure is realistic. Read more about specific sectors on our pages for manufacturing, retail and warehousing and public sector and education.

Once the system has paid back, the electricity it generates is close to free for the rest of its life, apart from maintenance. Panels typically carry performance warranties guaranteeing around 80% to 90% of original output after 25 to 30 years, so a system installed in 2026 should still produce most of its original output in the 2050s.

Over that period you should budget for:

• Inverter replacement: string inverters are commonly warranted for 5 to 12 years, so plan for at least one replacement during the system's life.
• Maintenance: periodic inspection, electrical testing and occasional cleaning.
• Roof works: if the roof needs replacing during the system's life, the panels must be removed and refitted at your cost.

That last point is why roof condition belongs in the payback discussion. Fitting solar to a roof with only ten years of life left can wipe out several years of savings when the array has to come off.

A payback forecast is only as good as the data behind it. The single most useful thing you can give an installer is 12 months of half-hourly consumption data, which most businesses with larger supplies can obtain from their supplier or meter operator. It shows exactly when you use electricity, so the installer can calculate self-consumption properly rather than guessing from an annual total.

When you receive proposals, check that each one states the self-consumption percentage, the import and export prices used, the inflation assumption and the degradation rate. Ask for a version with flat electricity prices too, and compare payback on that basis. Our guide to comparing commercial solar quotes sets out the full side-by-side checklist, and our commercial solar cost guide gives typical prices by system size.

When you are ready, compare quotes from up to three MCS-certified commercial installers for your site, using the same data pack.