Commercial solar panel installers: how to choose one that gets it right first time

Commercial solar installers: key facts for 2026

Commercial solar installers: the 10-point checklist

Every commercial solar installer will tell you they're the best. These are the ten things that separate the ones who are from the ones who aren't. Ask for evidence on each, in writing, before you sign.

MCS certification: when a commercial installer needs it, and when it doesn't

MCS is the UK's certification scheme for small-scale renewables. Its Installer Operating Requirements (Issue 2.0, September 2026) say MCS applies to installations up to a maximum capacity of 50kW for electrical technologies such as solar PV, and that its scope covers both domestic and commercial contracts. The solar installation standard, MIS 3002, covers systems up to a maximum DC output of 50kWp.

The reason it matters to a business is money. Ofgem's Smart Export Guarantee guidance sets out what certification you need to get paid for exported power:

Two practical points:

• Watch the 50kW line. A design that creeps from 50kW to 52kW crosses out of MCS, onto a bigger grid application form and, in England, into the planning glare check that applies to roof solar above 50kW (anything bigger isn't "microgeneration" in law). Ask the installer whether sizing just under the line, or well over it, suits your site better. See 50kW solar systems.
• MCS's own customer guarantees are written for domestic contracts. The rules on a written design and workmanship guarantee and MCS-approved financial protection sit under "domestic contracts". On a commercial contract, get the guarantee terms written into the contract itself.

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Installer websites are covered in logos. Here's what each one actually tells a business buyer.

On building regulations, the MCS solar standard says self-certification instead of building control approval is only allowed where the installer is registered with a competent person scheme for that work. Ask who is notifying building control, and how.

Grid connection: who handles G99?

Any solar system above 16 amps per phase needs approval from your distribution network operator (DNO) under the ENA's G99 process. That's roughly anything above 3.68kW on a single-phase supply or 11.04kW on three-phase, so almost every commercial system. Smaller systems use the simpler G98 process.

A good commercial installer runs the whole application. Using Electricity North West's process as an example:

• Up to 50kW: the ENA form A1-1 with a single line diagram.
• 51kW to 999kW: the ENA Standard Application Form, plus a G5 harmonics assessment.
• Export limitation: if the DNO caps how much you can export, the inverters are set to hold it, and a G100 form is submitted.
• Export meter: exports above 30kW need their own export MPAN.
• No switch-on until approved. The DNO reviews the commissioning documents before the system goes live.

Ask every installer: who submits the G99 application, how long the DNO usually takes in your area, and what happens to the design if export is limited. The full process is in our G99 application guide.

Roof surveys, structural checks and CDM

Any installer who quotes a commercial roof from a satellite image alone is guessing. A proper survey covers:

• Structure: can the roof take the panels, rails or ballast, plus wind and snow loads? On older or lightweight roofs, a structural engineer's calculation should back the design.
• Roof condition and life: panels should last 25 years or more. If the roof sheets or membrane need replacing soon, do that first.
• Asbestos: many pre-2000 buildings have asbestos cement sheets. The installer must see your asbestos register before planning fixings or cable routes.
• Fragile roof lights and access: edge protection, safe routes and covers for roof lights belong in the method statement.
• Electrical: switchboard capacity, inverter location, cable routes and DC isolation.
• Fire and insurance: tell your building insurer before installation and agree where inverters and isolators go.
• Planning: Most roof-mounted commercial solar in England is permitted development (the old 1MW cap was removed in December 2023), but bigger non-microgeneration systems need prior approval on glare, and listed buildings always need consent.

Your duties under CDM 2015

As a commercial client, the Construction (Design and Management) Regulations 2015 give you legal duties, not just the installer. HSE says commercial clients must make suitable arrangements, appoint a principal designer and principal contractor when more than one contractor is involved, give designers and contractors pre-construction information, make sure a construction phase plan exists and that welfare facilities are provided. A project must be notified to HSE if the work will last longer than 30 working days with more than 20 workers at any one time, or exceed 500 person days. A competent installer will explain all this without being asked.

Insurance, warranties and O&M: what to ask for in writing

Insurance

• Employers' liability: compulsory by law for any installer with staff, for at least £5 million. Ask for the certificate.
• Public liability: covers damage to your building or injury to third parties during the works.
• Professional indemnity: worth asking for when the installer designs the system, as it covers design errors.
• Contract works or all-risks cover: who insures the kit on site before handover?

Warranties

• Panel product warranty (defects) and performance warranty (output over time) come from the manufacturer. Ask for the datasheet and warranty document for the exact model quoted.
• Inverter warranty: check its length against the panels', ask what an extension costs, and ask whether the savings model allows for replacing the inverter during the system's life.
• Workmanship guarantee: the installer's own promise on fixings, roof penetrations and wiring. On a commercial contract, it only exists if it's written in.
• What if the installer stops trading? Ask whether any warranty is insurance-backed, and who honours it.

Operations and maintenance (O&M)

For bigger systems, a priced O&M contract is worth having: remote monitoring with alerts, a fault response time, periodic electrical inspection, cleaning where needed and inverter servicing. Ask for the monitoring login at handover, so you can see generation yourself.

How to compare commercial solar quotes per kWp

Lump-sum quotes hide everything. Divide each quote by its system size in kWp (the panels' peak rating) and you can compare like with like. The official benchmark:

Figures include VAT where it applied and exclude batteries. DESNZ measures cost per kW of declared net capacity (DNC). Installers usually quote per kWp of panels, and DESNZ says costs on that basis (total installed capacity) are typically 6-12% lower: the 10-50kW median is £1,204/kWp. Source: DESNZ solar PV cost data, published 28 May 2026. Systems above 50kW are outside the official series and are priced on survey. In the DESNZ data, cost per kW falls as systems get bigger.

A quote worth comparing lists:

• System size in kWp, the panel and inverter make and model, and the number of panels.
• Mounting system, and whether scaffolding, access, roof repairs and structural calculations are included.
• The G99 application and any DNO fees, and who pays if network works are needed.
• A generation estimate in kWh a year, with the assumptions behind it, and how much of that the site will use itself.
• Monitoring, warranties, and the price of an O&M contract.
• Payment stages and what triggers each one.

For prices by system size, see commercial solar panel costs and what a 50kW system costs. Homeowners should use our home solar panel costs guide instead.

Red flags: when to walk away from a commercial solar installer

• A price without a site visit, or a quote that never mentions the roof structure.
• A large upfront deposit with no link to delivery or commissioning, and no protection if the firm fails.
• "We'll sort the grid later." Without G99 approval, the system can't be switched on.
• Payback claims with no inputs. A savings figure is only as good as the electricity price, self-consumption and generation assumptions behind it. Ask to see them.
• Generation estimates that ignore shading, orientation or export limits.
• "Government grant" talk for business solar. There is no single national grant that pays for business solar, batteries or efficiency upgrades in England. The money comes from tax allowances, the business rates exemption, export payments, the Boiler Upgrade Scheme, the Workplace Charging Scheme and local or sector funds.
• Full expensing promised on solar panels. HMRC treats solar as special-rate plant. The Annual Investment Allowance is the lever (see below).
• No named panel or inverter model, or "equivalent" substitutions at the installer's discretion.
• Pressure to sign today, or a price that only holds for 24 hours.
• Vague answers on insurance, or certificates that never arrive.

The money an installer should get right

HMRC's manual is explicit: "all capital expenditure on the provision of solar panels is specifically designated as special rate" (CA22335). So the AIA is the big lever. A company spending £150,000 on a rooftop system can usually deduct the whole lot from that year's profits, as long as the AIA hasn't been used up on other kit.

Business rates: In England, plant and machinery used to generate or store power from on-site renewables (solar included, and batteries where the power stored is mainly or exclusively renewable) is excluded from rateable value until 1 April 2035. Wales (from 1 April 2024) and Scotland (from 1 April 2023) have equivalent exemptions running to 2035. Adding panels to your roof shouldn't raise your rates bill.

Export: The Smart Export Guarantee pays for solar you export, on systems up to 5MW in Great Britain. Suppliers set their own rates; the law only says the rate must be above zero, so shop around. More in solar capital allowances and commercial solar grants.

Commercial solar installers near me: how we help

Searching "commercial solar installers near me" gets you a list, and a list means a week of calls, sales visits and quotes you can't compare. Being local matters less than you'd think: what counts is commercial experience on roofs like yours, knowledge of your DNO's process, and someone who'll still answer in year ten.

We work differently. You tell us about the site once, and we pass your enquiry to one suitable installer that does commercial solar work in your area. Not a ring-round, and your details aren't sold on.

1. Tell us about the site: building type, roof, rough electricity use and your postcode. It takes two minutes.
2. One installer gets in touch to arrange a survey.
3. Survey and quote, sized to how the site uses power, with the grid, tax and rates position set out.
4. Check it against this page. Use the checklist above. You're under no obligation to go ahead.

Already have quotes? Use the 10-point checklist and the per-kWp benchmark to test them. Sector guides: warehouses, factories, farms, offices and schools.