What Does a Commercial Solar Installation Actually Cost?
The cost of a commercial solar panel system in the UK depends primarily on system size. Larger installations benefit from economies of scale, bringing the per-kilowatt-peak (kWp) price down significantly compared with smaller systems.
As a general guide, commercial solar installations currently cost between £700 and £1,100 per kWp fully installed. A typical 100kWp system sits at around £850/kWp, while smaller systems in the 10-30kWp range tend to cost more per kWp due to fixed costs being spread over fewer panels.
To put that into real numbers:
- A typical 20kWp system would cost approximately £18,000-£22,000
- A typical 50kWp system would cost approximately £42,500-£55,000
- A typical 100kWp system would cost approximately £70,000-£95,000
These figures include panels, inverters, mounting hardware, cabling, scaffolding, grid connection, and installation labour. VAT on commercial solar installations is charged at 20%.
What Is Included in the Installation Price
A commercial solar quote should break down into three main cost areas: equipment, installation, and grid connection.
Equipment costs
Solar panels typically account for 35-45% of the total system cost. Commercial installations generally use panels rated between 400W and 600W each. Inverters — the devices that convert DC power from the panels into usable AC electricity — make up another 10-15% of the total. Mounting systems, cabling, isolators, and metering equipment account for the remainder of the hardware costs.
Installation and labour
Labour, scaffolding, and project management typically represent 25-35% of the total cost. Flat roofs using ballast-mounted systems are generally cheaper to install than pitched roofs requiring rail-mounted brackets. Roofs that need structural reinforcement or have restricted access will increase costs further.
Grid connection and commissioning
Your installer will apply to your District Network Operator (DNO) for permission to connect. For systems under 16A per phase, this is usually free and straightforward. Larger systems may require a G99 application and could incur grid reinforcement charges if the local network lacks capacity.
Ongoing Costs After Installation
Once installed, commercial solar systems have relatively low running costs, but they are not zero.
Operations and maintenance (O&M) typically costs £7-15 per kWp per year. For a 100kWp system, that is roughly £700-£1,500 annually. O&M contracts usually cover remote monitoring, annual inspections, panel cleaning, and emergency callouts.
Inverter replacement is the main capital expense during the system's life. String inverters typically last 10-15 years, so you should budget for at least one replacement over the system's 25-30 year lifespan. Micro-inverters and optimisers generally carry longer warranties of 20-25 years.
Panel degradation is gradual — modern panels lose approximately 0.25-0.5% of output per year, meaning a system will still produce around 85-90% of its original output after 25 years.
How System Size Affects Your Return
The financial return from commercial solar depends on how much of the generated electricity you use on-site versus how much you export to the grid.
Each kWp of solar capacity generates approximately 850-1,000 kWh per year in the UK, depending on location and roof orientation. At current commercial electricity rates of 24-34p/kWh, every kilowatt-hour you use on-site avoids a direct cost. Electricity you export earns a lower rate through the Smart Export Guarantee (SEG), currently 5-15p/kWh depending on your supplier.
This is why system sizing matters. A business operating Monday to Friday during daylight hours might self-consume 60-80% of generation with a well-sized system. Oversizing beyond your daytime demand means more exported electricity at the lower SEG rate, which weakens your payback.
A typical well-sized commercial system achieves a payback period of 4-8 years, after which you benefit from effectively free electricity for the remaining 17-22 years of the system's life.
Tax Relief and Financial Incentives
The Annual Investment Allowance (AIA) allows businesses to deduct the full cost of qualifying plant and machinery — including solar panels — from taxable profits. The current AIA limit is up to £1 million per year, meaning most commercial solar installations can be fully deducted in the year of purchase.
With the main corporation tax rate at 25%, a £85,000 solar installation could reduce your tax bill by £21,250 in the first year. This effectively reduces your net cost and shortens payback further.
The Smart Export Guarantee requires licensed electricity suppliers to offer export tariffs to small-scale generators with solar PV capacity up to 5MW. Rates vary between suppliers, so it is worth comparing tariffs before choosing an export contract. Ofgem's guidance confirms that SEG tariff rates must always be above zero, but the actual rate is set by each supplier individually.
The UK government's Solar Roadmap, published in 2025, sets out over 70 actions to expand solar deployment, including streamlining grid connections — a signal that policy support for commercial solar remains strong.
What to Check Before You Commit
Before accepting a quote for commercial solar, consider these practical points:
- Roof space: Allow 6-8m² of roof space per kWp on a flat roof, accounting for row spacing and maintenance access. A 50kWp system needs approximately 300-400m² of usable roof area.
- Roof condition: If your roof needs replacing within the next 10 years, do that first. Removing and reinstalling panels adds unnecessary cost.
- Planning permission: Most rooftop commercial solar qualifies as permitted development under current planning rules. However, listed buildings, conservation areas, and installations that protrude significantly above the roofline may require a planning application.
- MCS certification: Ensure your installer is MCS-certified. This is required if you want to claim SEG export payments and is a strong indicator of installation quality.
- Multiple quotes: Get at least three quotes from MCS-certified installers. Prices vary significantly between contractors, and the cheapest quote is not always the best value.
A well-specified commercial solar system is one of the most predictable investments a UK business can make. The equipment is proven, the financial incentives are clear, and electricity costs remain significantly higher than pre-2021 levels. The key is getting the system size, installer, and financing structure right for your specific building and energy profile.
