How do you choose a commercial solar installer?

Choose a commercial solar installer by comparing the proposed design, survey evidence and contract scope. Eligible solar installations in Great Britain can investigate export payments up to 5 megawatts [S1], but eligibility does not establish your income. Ask each bidder to use the same electricity data and explain roof, network and maintenance responsibilities before you commit. Checked October 2026.

Last checked 16 October 2026

How do you choose a commercial solar installer?

Start with the evidence you want back. Give each bidder the same electricity records, site drawings and operating hours. Ask for a design proposal with an itemised price, rather than a panel count and an annual bill reduction. Your objective is a system you can understand, maintain and use within your property rights.

For a commercial construction project, HSE places duties on the client to make suitable management arrangements, appoint people with appropriate skills and provide relevant information [S2]. Selecting a contractor does not replace those responsibilities. Ask who will design the project, supervise the work and coordinate subcontractors.

Request evidence of comparable commercial work, with the customer’s permission to contact them. Ask what changed between the initial design and completion. A useful reference can explain disruption, handover and fault handling; a star rating cannot answer those questions. Verify any certification claimed against its issuing body’s current register and check that its scope covers the proposed work. Do not treat a badge as proof of roof competence.

How can you compare commercial solar installation quotes?

Use a common comparison sheet. Mark each item included, excluded or awaiting survey. Leave an unresolved item visible instead of assigning it a zero cost. Read the commercial solar cost guide alongside this exercise.

This is a suggested purchasing checklist. Ask bidders to explain different scopes before comparing totals. A quote that excludes strengthening or electrical alterations is a different proposition from one that includes them. Keep a written schedule of provisional sums and the events that can change the price.

The distribution network operator, or DNO, manages your local electricity network. G99 is the engineering recommendation used for relevant generation connections. The network’s process can involve an application, connection offer, reinforcement and commissioning tests [S3]. Ask your own DNO to confirm the route for your site; do not let the installer describe an application as an accepted connection.

How do you test an installer’s output and payback figures?

A kilowatt (kW) measures power; a kilowatt-hour (kWh) measures energy. Kilowatt-peak (kWp) describes the panel array’s rated output under test conditions. Ask for annual generation in kWh, the share used on site, exported energy and any generation curtailed by a network limit. Keep these quantities separate in the comparison.

PVGIS, the European Commission’s Photovoltaic Geographical Information System, produces monthly and annual generation estimates from a stated design [S4]. Request the model inputs and output file. Then ask the bidder to match generation timing to your demand. Read commercial solar sizing if a proposal uses annual consumption alone.

For your review, separate avoided electricity purchases from cash export receipts. Ask which unit rate was used, which bill charges remain and whether maintenance and replacement costs were deducted. A headline payback without those workings is incomplete. Obtain a downside calculation for lower output, lower daytime demand and a less favourable export contract. These are tests to request, rather than forecasts for your site.

Ofgem’s Smart Export Guarantee allows eligible generation in Great Britain to seek payment for metered exports. Suppliers determine rates and contract terms [S1]. Do not accept an assumed household export rate as your business offer. Northern Ireland needs its own export arrangements.

What roof checks and contract terms should you request?

HSE identifies rooflights and roof sheets among potentially fragile surfaces and says roof work needs precautions against falls [S5]. Ask how the survey and installation will be performed safely. Do not send your staff onto a roof to take measurements. Use the roof suitability guide to prepare existing records and define the assessment scope.

Ask for a clear responsibility schedule covering roof leaks, damage, electricity interruptions and repairs. Request copies of relevant insurance evidence and the process for reporting faults. Specify who can access monitoring data if the original installer stops trading. Separate the manufacturer’s product support from the contractor’s labour obligations, and have your solicitor check disputed liability wording.

For fully funded, part funded and self funded offers, compare ownership and operation as carefully as price. Ask about roof access, lease length, relocation, redevelopment, assignment, early termination and removal. Identify who receives export income and who pays network charges. A fully funded offer should state any host rent or revenue share explicitly; do not infer one from the absence of an installation invoice.

If chargers are included, obtain a separate parking and access plan. Record bays unavailable during installation, any permanent equipment footprint and who resolves driver complaints. Solar installation scope alone does not settle the operating responsibilities of a charging service.

What should you do next?

Prepare a common brief, list unresolved exclusions and request revised offers against that brief. Compare the funding contract guide before committing to a long term agreement. Ask your accountant to review tax assumptions and your solicitor to review property and exit terms.

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