30kW commercial solar — cost, ROI & payback

At around 30 kWp, a system sits at the small end of commercial installations. Fixed costs — scaffolding, design, the DNO connection application and commissioning — are spread across fewer panels, so the price per kWp is higher than on a large warehouse roof. Typical 2026 supply-and-install pricing at this scale runs roughly £950–£1,300 per kWp, which puts a 30 kWp system at about £28,000–£33,000 excluding VAT. We use a central estimate of £30,000 (about £1,000/kWp) below.¹

Cost falls sharply with size: the same installer that quotes ~£1,000/kWp at 30 kW may be nearer £650–£750/kWp at 250 kW. If your roof is larger, it is worth comparing the 50 kW and 100 kW options, or return to the commercial solar hub for the full size ladder.

This assumes a standard pitched or flat commercial roof in reasonable condition. Add-ons that change the price include battery storage, roof strengthening, a half-hourly meter upgrade, or a more complex grid connection.

A well-oriented UK roof produces roughly 950 kWh per kWp per year, a standard planning figure for southern-to-central Britain. A 30 kWp system therefore generates about 28,500 kWh a year — an estimate that varies with location, roof pitch, orientation and shading. You need around 7 m² of roof per kWp, so budget for roughly 210 m² of usable, unshaded roof.

The value of solar comes mostly from self-consumption — power you use on site instead of buying from the grid. Commercial self-consumption typically runs 60–85% depending on sector: a warehouse or office that operates 9-to-5 sits at the higher end, while a site with heavy evening or weekend demand sits lower. We model a mid-range 70% below.

• Generated: ~28,500 kWh/year
• Self-consumed (70%): ~19,950 kWh — offsetting grid electricity
• Exported (30%): ~8,550 kWh — paid via a Smart Export Guarantee tariff⁵

The saving is the grid electricity you avoid buying, plus a smaller amount of export income. The latest DESNZ figures put the average non-domestic electricity price at about 24p per kWh including the Climate Change Levy; many SMEs on fixed contracts pay more (26–30p/kWh).¹ We use 25p/kWh as a conservative central estimate, and a typical Smart Export Guarantee rate of 5p/kWh for exports.⁵

On a £30,000 installed cost, that is a simple payback of about 5.5 years (£30,000 ÷ £5,415). At a higher tariff of 28p/kWh the payback shortens to roughly 5 years; at a lower 22p/kWh it lengthens to around 6 years. The tax relief below improves the effective net cost further. These are estimates — an installer's site survey will refine them against your actual half-hourly data.

Two tax points matter, and both are worth confirming with your accountant.

VAT. The 0% VAT rate on solar applies to domestic (residential) installations only — commercial solar pays the standard 20% VAT.⁴ A VAT-registered business can normally reclaim that input VAT, so it is a cash-flow point rather than a permanent cost, but do not budget as if commercial solar is zero-rated.

Capital allowances. Solar PV is classified by HMRC as special-rate plant and machinery. That means it qualifies for the 50% first-year allowance — you can deduct 50% of the cost against taxable profits in year one, with the balance entering the special-rate pool for 6% writing-down allowances thereafter.² Solar does not qualify for 100% full expensing, which applies only to main-rate assets.³

On a £30,000 spend, the 50% first-year allowance shelters £15,000 of profit in year one. At the 25% main corporation tax rate that is roughly £3,750 of tax saved in year one, with the remaining pool relieved over subsequent years — an estimated total tax benefit of around £7,500 over the asset's life.

Panels are typically warrantied for performance over 25 years, degrading slowly (around 0.5% a year). Holding the annual benefit flat at roughly £5,400 and allowing for that gentle output decline plus one inverter replacement (around £2,000–£3,000, typically in the 10–15 year window), the picture over 25 years looks like this:

• Cumulative benefit (25 yrs): an estimated £120,000–£130,000 at today's tariff
• Less installed cost: £30,000
• Less one inverter replacement: ~£2,500
• Plus capital-allowance tax relief: ~£7,500
• Estimated net lifetime benefit: roughly £95,000–£105,000

That is a net return of about three times the outlay over the asset's life — an estimate that rises if grid electricity prices climb (as they have historically) and falls if your self-consumption is lower or your tariff is cheaper. It excludes any financing cost if you borrow to fund the system. If you would rather avoid the upfront capital altogether, compare ownership against a power purchase agreement on our buy vs PPA page.

A 30 kWp system suits a business with around 210 m² of usable roof and an annual electricity bill in the region of £7,000–£15,000 — enough daytime demand to absorb most of the ~28,500 kWh generated. Typical fits include a small industrial unit, a workshop, a mid-size retail or hospitality site, a farm building, a car showroom, a GP surgery or a small school block.

If your bill is much larger or your roof is bigger, a 30 kW system will under-size your demand and you will leave savings on the table — step up to 50 kW, 100 kW or 250 kW. If it is smaller, look at 10 kW or 20 kW.

Sizing also depends on how your sector uses power through the day. See the tailored guidance for a warehouse, factory, farm, school, retail unit or hotel, and read how to choose an installer before you commit.