Commercial solar panels: what UK businesses need to know before buying

Commercial solar panels cost UK businesses roughly £700 to £1,200 per kW installed in 2026, and most rooftop systems pay back in four to eight years. The return depends almost entirely on how much of the power you use on site rather than export. Planning permission is rarely needed. A grid connection almost always is.

The number that decides whether a project works is not the panel price. It is the gap between what you pay for a unit of grid electricity and what you get paid for a spare one you send back, and right now that gap runs at something like six or seven to one. Most quotes skate past it. Ask for half-hourly modelling rather than an annual total, because a warehouse that shuts at four on a Friday has a completely different shape of demand from a chilled food unit that never stops.

The assumptions behind every figure on this page

• Location. A Midlands rooftop, south-facing, 10 degree tilt, minimal shading. Worked example only.
• Yield. 950 kWh per kWp per year, using the MCS MIS 3002 methodology. The range across Great Britain runs from roughly 837 to 1,132.
• Import price. 25p per kWh. Indicative. Check your own contract, and the DESNZ Quarterly Energy Prices tables for your consumption band.
• Export price. 4p per kWh, the middle of current fixed Smart Export Guarantee business tariffs.
• Self-use share. 55% without a battery. The typical commercial range is 40% to 55%.
• Capital cost. £850 per kW, the mid-point of published 2026 pricing at 250 kWp scale.
• Corporation tax. 25%, the main rate. Yours may differ.

What commercial solar costs in 2026

Price per kW falls as the system gets bigger, because scaffolding, design and grid work do not scale with panel count. Published 2026 pricing sits roughly here:

• Under 100 kW. £900 to £1,200 per kW. A 50 kW system lands near £45,000.
• 100 to 500 kW. £750 to £950 per kW. A 250 kW system lands between £180,000 and £230,000.
• Above 500 kW. £700 to £850 per kW. A 500 kW system lands between £350,000 and £425,000.

Those headline numbers usually cover panels, mounting, inverters, AC and DC cabling, commissioning and a basic monitoring platform. What they often exclude is where budgets break:

• scaffolding and edge protection on a tall or awkward building
• structural surveys and roof strengthening works where roofs cannot take the extra load
• an asbestos survey, and removal if sheets get disturbed
• a long cable run from roof to switchroom, which on a large building can be hundreds of metres
• switchgear or transformer upgrades
• civils works to facilitate cable routes and electrical upgrades
• the DNO's assessment fee, and any network reinforcement it triggers
• a half-hourly export meter
• ongoing operations and maintenance, typically £8 to £15 per kW per year

Your load profile decides the savings

A unit you use yourself is worth roughly 25p. The same unit exported is worth about 4p. That one fact drives everything else.

With no battery, a typical commercial site uses between 40% and 55% of what it makes. Add a well-sized battery and that can rise to somewhere between 75% and 90%. The difference in cash terms is large, though a battery has to earn its own capital cost first, which is a separate sum covered further down.

So the first question is not "how big is my roof?" It is "when do I use power?" A few patterns:

• Strong fit. Manufacturing on a day shift, cold storage, data rooms, supermarkets, hotels, leisure centres with pools, care homes, offices with heavy cooling loads.
• Awkward fit. Sites that run mainly at night, seasonal operations, buildings that sit empty at weekends, tenanted units where the landlord pays for the kit and the tenant gets the saving.
• Needs a workaround. Low daytime base load but a big roof. Look at export-limited design, a battery, or shifting a process into daylight hours.

Payback, and how to stress-test a quote

The arithmetic on a 250 kWp rooftop system

Using the assumptions above, in order:

1. Annual generation: 250 kWp at 950 kWh per kWp gives 237,500 kWh.
2. Used on site at 55%: 130,625 kWh at 25p is worth £32,656.
3. Exported at 45%: 106,875 kWh at 4p is worth £4,275.
4. Gross annual benefit: £36,931.
5. Less operations and maintenance at £12 per kW: £3,000.
6. Net annual benefit: £33,931.
7. Capital cost at £850 per kW: £212,500.
8. Simple payback before tax relief: 6.3 years.
9. Claim the full £212,500 against taxable profit under the Annual Investment Allowance and, at 25%, you save £53,125 in corporation tax.
10. Effective capital cost: £159,375.
11. Payback after tax relief: 4.7 years.

The four things that move that answer

1. Yield. Inverness gets 837 kWh per kWp on a south-facing roof. Brighton gets 1,132. That is a 35% swing on identical kit, and it changes payback by well over a year.
2. Self-use share. Drop from 55% to 35% and the net benefit falls by about £5,000 a year.
3. Your import price. A site on a legacy fixed contract at 18p sees a very different case from one paying 30p.
4. Degradation. Output falls by roughly 0.4% to 0.55% a year on a decent panel. Over 25 years that matters for lifetime return, though barely at all for payback.

Ask for the model as a spreadsheet, not a PDF summary. Then change the self-use assumption yourself and watch what happens. If the case only stands up at 80% self-use with no battery, the case does not stand up.

Planning permission: usually no, sometimes yes

Most rooftop solar on non-domestic buildings in England is permitted development under Class J of the 2015 General Permitted Development Order. In December 2023 the government removed the old 1 MW capacity ceiling from Class J, so array size on its own no longer forces a full planning application.

You are not off the hook entirely. Class J carries conditions, and you still apply to the local planning authority for a determination on whether prior approval is required. Panels must not stick out more than 200mm from the roof plane, must sit at least a metre from the roof edges, and must not become the highest point of the building.

Where you do need full planning permission:

• listed buildings, and scheduled monuments
• some sites in conservation areas, world heritage sites and national parks
• ground-mounted arrays above the small permitted development thresholds
• solar carports, which are structures in their own right

Scotland, Wales and Northern Ireland run separate planning regimes with different thresholds. Check the local rules rather than assuming the English position travels.

The grid connection is what slips

Anything above 16 amps per phase needs approval from your distribution network operator under Engineering Recommendation G99. On a three-phase supply that threshold sits around 11 kW, so it catches essentially every commercial system. There are two routes.

Fast track

Fully type-tested equipment up to roughly 50 kW three-phase, submitted on ENA Form A1-2. Faster, and cheaper.

Full G99

Everything larger. Expect an acknowledgement within a few working days and a formal connection offer inside the DNO's published standard, commonly quoted as 65 working days.

This is the stage that derails timelines, so start it early. Two practical points rarely appear in sales material.

First, if the DNO restricts your export capacity, the project is often still fine. An export-limited or zero-export design uses a grid meter and an inverter control loop to hold export at or below the agreed figure. Since a self-used unit is worth six times an exported one anyway, a cap on export costs far less than most people assume.

Second, the connection offer may arrive with a reinforcement cost attached. Ask for a budget estimate before you commit to a design, not after.

Grants, tax relief and business rates

The honest answer on grants first, because a lot of pages are vague about this. As of September 2026 no open national grant pays for solar on private-sector commercial buildings in Great Britain. The UK Shared Prosperity Fund, which was the main route for SME solar grants in 2024 and 2025, closed at the end of March 2026. The Local Growth Fund that followed it in April 2026 is aimed at mayoral city regions in the North and Midlands, and at infrastructure and skills, so it is not a solar grant scheme you can apply to directly.

What is real, and worth more than most of those grants were:

Annual Investment Allowance

A 100% deduction against taxable profit in year one, up to £1m of qualifying spend a year. The limit is shared across a group, but it covers most commercial systems in full.

50% first-year allowance

Companies can claim 50% on new and unused special rate assets. This matters where the AIA is already used up. Solar counts as a special rate asset, which is also why full expensing is not available on it.

Writing down allowances

6% a year on a reducing balance, on the special rate pool. The slow route. Use the AIA first.

Business rates exemption

Eligible on-site renewable generation and storage is exempt in England from 1 April 2022 to 31 March 2035. The Valuation Office Agency applies it by leaving the plant out of the rateable value, so there is nothing to claim. Ground-mounted solar farms are treated differently.

Smart Export Guarantee

Payment for the units you export, at a rate your supplier sets and must keep above zero. Eligible up to 5 MW of capacity. Rates vary hugely between suppliers, so shop around rather than defaulting to whoever supplies your import.

Get your accountant to confirm the position for your own company before you sign anything. Rates and allowance limits move at fiscal events, and the classification of solar as a special rate asset catches out people who assume full expensing applies.

Own it, lease it, or sign a PPA

Buy outright

You pay the full capital cost and own the system from day one. Best when you have the cash and enough taxable profit to absorb an AIA claim. Highest lifetime return of the three.

Lease or asset finance

A deposit, then payments across five to ten years, with ownership at the end. Best when you want to own it but would rather spread the cost.

Power purchase agreement

No upfront spend. A funder installs and maintains the system, you buy the power it makes at an agreed rate below your grid price, and ownership usually transfers at the end of a 10 to 25 year term. Best when capital is genuinely unavailable, or the balance sheet matters more than lifetime return.

The trade with a PPA is lifetime cost. Buying outright works out meaningfully cheaper across 25 years, and you keep the tax relief and the export income. A long PPA also sits on the building, which can complicate a sale or a move if the incoming occupier will not take it on. Read the exit terms and the rate escalator before anything else. An index-linked PPA rate that climbs with RPI can overtake your grid price if wholesale prices fall.

Can your roof actually take it?

Panels last 25 to 30 years. Putting them on a roof with eight years left in it is an expensive mistake, because you pay twice to take them off and put them back. Check roof life first, design second. A proper survey covers:

• Structure. Can the purlins and frame carry roughly 12 to 20 kg per square metre, plus wind uplift on a ballasted flat roof system? A structural engineer signs that off, not the installer's salesperson.
• Sheet type and condition. Asbestos cement is common on industrial buildings put up before 1999. It does not rule out solar, but it changes the fixing method, the cost and the legal duties.
• Remaining life. If the roof needs replacing within ten years, do both jobs together.
• Orientation and pitch. An east and west split array makes less at midday but more at each end of the day, which often suits a business load better than a pure south array.
• Shading. Plant, flues, parapets, neighbouring buildings. Optimisers or multiple MPPT strings can mitigate it, at a cost.
• Access and egress. Fall protection, walkways, and how anyone will safely clean or service the array later.

Batteries: when they earn their keep

A battery makes sense when the shape of your demand, rather than its size, leaves value on the table. Three cases where it usually pays:

1. Heavy evening or early morning load. Store cheap midday output, use it once the sun has gone.
2. Expensive network charges. If your site is on a half-hourly meter with red band distribution charges on weekday late afternoons, discharging through that window can save more than the solar arbitrage does.
3. A capped export limit. Where the DNO restricts export, a battery soaks up power you would otherwise throw away.

Cases where it does not pay: a nine to five office with a modest roof, or any site already using 80% of what it makes. You cannot save the same unit twice, and a battery that cycles half as often as the model assumed doubles its payback.

Choosing an installer

Six questions worth asking, and what a good answer sounds like:

1. "Show me a system you put in three or more years ago, with its actual generation data." A serious contractor has monitoring history. Vagueness here is telling.
2. "Who does the structural sign-off, and is it included?" It should be a named engineer, and it should be in the price.
3. "What is your G99 track record with my DNO?" Regional experience shortens timelines.
4. "What exactly is warranted, and by whom?" Separate the panel product warranty, the panel performance warranty, the inverter warranty and your installer's own workmanship warranty. Those are four different things with four different durations.
5. "What happens if generation comes in below your model?" Ask whether they offer any performance guarantee at all.
6. "What does the O&M contract cover, and what does it cost a year?" An inverter replacement at year 12 should already sit in your financial model.

Look for MCS certification on smaller systems, NICEIC or NAPIT electrical registration, and membership of a trade body such as Solar Energy UK. Check the trading history of the legal entity, not just the brand. A warranty is only worth as much as the company standing behind it.

What the timeline really looks like

Stage by stage, for a mid-sized rooftop scheme:

• Enquiry to site survey: one to two weeks.
• Design, structural check and quote: two to four weeks.
• G99 application to connection offer: three weeks on the fast track, up to 13 weeks or more for a full application.
• Prior approval determination: about eight weeks with the local planning authority.
• Procurement and scheduling: four to eight weeks.
• Installation of a 250 kWp system: two to four weeks on site.
• Commissioning and meter change: one to three weeks.

Four to eight months from first call to switch-on is realistic. Grid and planning run in parallel, so the total is shorter than the sum of the parts. Anyone promising six weeks is either working on something very small, or has not applied to the DNO yet.

Questions businesses ask

How much do commercial solar panels cost in the UK?

Installer pricing published in 2026 puts sub-100 kW systems at roughly £900 to £1,200 per kW, 100 to 500 kW at £750 to £950 per kW, and anything above 500 kW at £700 to £850 per kW. A 250 kWp rooftop array therefore sits near £180,000 to £230,000 before tax relief. Scaffolding, roof strengthening and DNO fees are the main swing factors.

How long do commercial solar panels take to pay back?

Four to eight years is the usual range for a business that uses most of its generation on site. A company paying the 25% main rate of corporation tax and claiming the Annual Investment Allowance effectively cuts the capital cost by a quarter, which typically pulls payback in by more than a year. Low daytime demand pushes it the other way.

Do commercial solar panels need planning permission?

Most rooftop arrays on non-domestic buildings in England fall under Class J permitted development, and the old 1 MW capacity cap went in December 2023. You still apply to the local planning authority for a prior approval determination. Listed buildings, scheduled monuments and some conservation area sites need full permission.

Are there grants for commercial solar panels?

No open national grant pays for solar on private-sector commercial buildings in Great Britain as of September 2026. The UK Shared Prosperity Fund closed at the end of March 2026. Tax relief and the business rates exemption are the dependable support. Some combined authorities and rural funds run local schemes, so it is worth a check.

How long do commercial solar panels last?

Panels carry 25 to 30 year performance warranties and typically still make around 85% of their original output at year 25. Inverters are the shorter-lived part, usually 10 to 15 years, so budget for at least one swap. The roof underneath is often the real constraint, which is why roof life gets checked before design.

Your next step

Get your last 12 months of half-hourly consumption data from your supplier before you speak to anyone. It is free, it takes one email, and it turns a sales conversation into an engineering one. With that file in hand, any competent installer can model your actual self-use share rather than guessing at it, and you can compare three quotes on the same basis.