How it works

Our model uses commercial-scale assumptions, not residential ones. The three inputs that drive the result:

• Solar yield — a base of 950 kWh per kWp per year, adjusted by region using long-run UK irradiance data. South-facing roofs and warmer southern counties produce more; Scotland and the North East produce less.
• Self-consumption rate — we assume 72%, meaning most of the generation is used on-site. The rest is exported to the grid at SEG rates (we use £0.06/kWh as a conservative average).
• Your electricity rate— we default to £0.28/kWh based on Ofgem's 2026 non-domestic benchmark. You can edit this to match your actual contract.

Installed cost is set at £900 per kWp, typical for UK commercial installations between 30 and 250 kWp. Smaller systems (under 20 kWp) tend to cost more per kWp; very large systems can be cheaper.

We hold a buyer's perspective. The point of the guides is to give you the questions an installer might prefer you didn't ask — and to do it in plain English, without industry hedging.

When we say something is true, we cite where the number came from (Ofgem, MCS, the SEG suppliers' published rates). When we say something is contested, we say so.

smesolar.co.uk is funded three ways, all of them disclosed:

• Display advertising — standard Google AdSense placements in sidebars and within articles. Ads are clearly marked and never integrated into the calculator output.
• A single Featured Partner— one MCS-accredited installer at a time, paying a flat monthly sponsorship fee. Their logo appears on the calculator results and the foot of guides; we don't take per-lead fees. See Featured Partner for the spec.
• The Brief — our free monthly email. Subscribers sometimes click affiliate links in our guides or in the Brief (typically to UK energy comparison tools or solar finance providers); we earn a small fee when they do. Affiliate links are always marked.

We don't sell leads to installers. We don't take per-quote commissions. We don't resell email addresses. The point is to stay credible to the SMEs reading the site — that's the only asset we have.

We are not an installer. We don't fit panels, employ engineers, or take a margin on installs. We don't run a quote-comparison marketplace, and we won't pass your details to a network of installers.

When you're ready to get an actual quote, you'll choose an installer yourself — directly, from a longer list, or via a comparison platform we link to in the guides. Either way, the decision and the contract are yours.