Solar Panels for Small Business: costs, payback and suitability

Small business solar is a smaller, simpler version of a commercial install — but it has one qualifying question that catches people out, and we would rather raise it up front than waste your time. This guide sets out the real costs and the tax treatment independently. We don't install anything; when you want a figure for your premises, the calculator gives you one in about a minute.

Why small business premises work for solar

Most small commercial operations run during the day, and that is what makes solar pay. A shop, cafe, workshop, salon, surgery or small unit draws power for lighting, refrigeration, cooking, tools or cooling in the same hours a rooftop array generates it. Every unit you generate and use yourself displaces a grid unit costing around 25p per kWh, so the more of your generation you consume on site, the faster the system pays back.

Roof area is rarely the constraint at this scale. At roughly 6 m² per kWp, a 25 kWp system needs around 150 m² of usable roof — within reach of most small commercial buildings. The real constraint, and the reason we ask early, is the electricity supply.

The question that decides it: three-phase or single-phase

This is the central qualifier for small business solar, and it is worth being honest about because it mirrors how our own assessment works. Most small commercial solar systems need a three-phase electricity supply. Single-phase premises — common for smaller shops, offices and units — are usually capped at a smaller system size, which limits how much solar is viable.

We flag this deliberately. If a single-phase cap means solar won't do much for your premises, that is useful to know in a minute rather than after a sales visit. Our payback and ROI guide explains what else can hold returns back, from shading to low self-consumption.

What does small business solar cost?

Small business systems sit at the smaller end of the commercial range, where the cost per kWp is highest because fixed costs — scaffolding, design, grid paperwork — spread over fewer panels. As a guide for 2026:

That works out at roughly £1,278–£1,500 per kWp at this scale. The headline figure isn't the whole story, because the tax treatment claws a large part of it back — and because what matters is the cost against the savings it unlocks. Our commercial solar cost guide breaks down exactly what sits inside a quote.

The tax relief that covers the cost

For most small businesses, the single biggest piece of support is not a grant — it is the tax system. The £1m Annual Investment Allowance lets a business deduct 100% of a qualifying solar system's cost from its year-one profits, worth about 25% of the project back at the 25% corporation tax rate. Because small business systems cost well under £1m, the AIA covers the full cost for most SMEs.

Commercial solar is also exempt from business rates in England, and a small number of regional grants exist. There is no universal UK solar grant, though — our grants and tax relief guide keeps a current list by nation and explains what is and isn't real.

Is your small business suitable? A quick checklist

A few questions settle most cases before a survey:

• Electricity supply — the first thing to check. Three-phase opens up the usual system sizes; single-phase usually caps you to a small system.
• Roof size and condition — clear, structurally sound roof with at least 10 years of life left, around 6 m² per kWp.
• Daytime use — the more you consume while the sun is up, the better the return; a business that is busy through the working day is the ideal fit.
• Tenure — owner-occupiers have the simplest path; if you lease, you need landlord consent and enough lease left to recoup the cost.

Do small businesses need planning permission?

Usually not. Since December 2023, permitted development rights cover rooftop solar of any size on commercial buildings in England, provided the panels sit at least 1m from the roof edge and don't protrude more than 200mm on a pitched roof, or 1m on a flat roof. The main exceptions are listed buildings, scheduled monuments and conservation areas — worth checking if your premises is in an older high street or town centre. Building regulations always apply. Full detail is on our planning permission guide.

Updated June 2026 · By Taro Schenker, founder of Business Solar Check. We're independent — we don't install solar. Figures are indicative UK averages; your site survey confirms the numbers for your roof.