How much does commercial solar cost in 2026?

If you’re pricing a commercial solar installation in the UK in 2026, the honest answer is simple. Cost depends almost entirely on system size. Everything else matters far less than most sales material suggests.

Per-kWp cost falls sharply as scale increases. At 100kW, expect roughly £800–£1,000/kWp. At 1MW and above, that drops to £600–£720/kWp.

This happens because fixed costs — scaffolding, cabling, commissioning, project management — spread over more panels as systems grow larger. The underlying technology stays the same; only the economics of scale change.

Cost by system size

System size	Typical installed cost	Typical payback	Best fit
100kW	£80,000–£100,000	5–7 years	Offices, standalone retail, small warehouses (~500–650m² roof)
250kW	£175,000–£215,000	4.5–6.5 years	Larger warehouses, distribution units, business parks (~1,300–1,600m²)
500kW	£300,000–£375,000	4–6 years	Large distribution centres, factories, cold storage (~2,600–3,200m²)
1MW+	£600,000–£720,000+	4–6.5 years	Major logistics/manufacturing campuses, multi-building estates, ground-mount

These are installed-cost ranges, not fixed quotes. Site condition, roof type, grid connection distance, and current market pricing all move the final number. We cover each band in more detail on our commercial solar cost pages.

The tax mistake almost everyone makes

Most commercial-solar marketing tells you that solar qualifies for the UK’s 100% “Full Expensing” first-year tax relief. It doesn’t — and getting this wrong changes your real, net-of-tax payback.

Since 2012, HMRC has classified solar panels as “special rate” expenditure, not main-rate plant and machinery. This sits under its capital allowances rules (Capital Allowances Manual CA22335). Full Expensing — the 100% first-year deduction with no cap — applies only to main-rate assets. Solar doesn’t qualify.

What solar actually gets:

1. The Annual Investment Allowance (AIA) gives 100% relief on qualifying expenditure. The cap is a shared £1 million a year across all your qualifying capital spend. For most single-site commercial arrays, this comfortably covers the whole cost.
2. Above the AIA cap, the 50% special rate first-year allowance on the remainder.
3. The balance after that, written down at 6% a year in the special rate pool.

The 2026 Budget changed the main pool. It introduced a new 40% first-year allowance and cut the main-rate writing-down allowance from 18% to 14%. However, none of that touches solar’s special-rate treatment — those changes apply to a different pool entirely.

In practice, this often works in the business’s favour. Say your business hasn’t used its AIA elsewhere in the accounting year. A system at any of the four bands above will typically fall entirely within the £1m cap. That gets you a genuine 100% first-year deduction — just via the AIA, not “Full Expensing.”

If your business has already committed the AIA to other capital spend, the real relief looks different. It’s 50% in the first year, then 6% a year after that. This changes the payback maths meaningfully.

We model this against your actual capital programme, not a generic assumption. See our energy and ROI modelling service.

What actually drives the cost within a band

• Roof type and condition. A straightforward flat or low-pitch commercial roof in good condition is the cheapest scenario. Ageing sheeting, asbestos-containing roofing, and roofs that need reinforcing before they can take the load all add cost. Assess these before you accept a quote, not after.
• Grid connection. Systems above the smallest scale go through Engineering Recommendation G99. This means a DNO application and, for larger systems, a technical capacity assessment. Where local grid headroom is limited, reinforcement costs can be significant and easily underestimated, particularly in rural areas.
• MCS accreditation. The MCS solar PV installation standard (MIS 3002) applies only up to 50kWp. Above that, treat every band as a genuine commercial project. Specify, commission and warranty it properly — don’t just scale up a domestic-scheme template.

Getting a number you can actually rely on

A quote is only as good as the assumptions behind it. Before you commit capital, an independent feasibility study gives you the real, site-specific numbers. That means actual roof or land capacity, realistic yield, and grid headroom. It also means capex and payback net of the capital allowance treatment that genuinely applies to your business — not a generic per-kWp rule of thumb.