A commercial installation is a construction project on your premises, with programme risk, structural implications and a network connection to obtain. The installer needs to be capable of all of that, not just of fitting panels.
Last reviewed 4 Nov 2026.
What to check
Certification The Microgeneration Certification Scheme (MCS) for systems up to 50kW, and the equivalent route above that. Ask which applies to your project and ask to see the certification.
Commercial track record Domestic and commercial are different disciplines. Ask for reference projects of comparable size on comparable buildings, and actually call one.
Structural competence Who assesses the roof, and are they qualified to? A commercial roof, particularly profiled metal or a flat membrane, needs a proper structural assessment and a view on the remaining life of the covering.
Grid connection experience Have they managed G99 applications with your distribution network operator before? This is often the longest item in the programme and experience shows.
Insurance Public liability and professional indemnity at levels appropriate to the contract value. Ask for certificates.
Health and safety Working at height on a commercial building, with your staff below. Ask for their method statements and risk assessments, and check they hold a relevant safety accreditation.
Financial standing You are making stage payments to a firm that will be holding your money. Check the accounts. This is normal commercial diligence and no reasonable firm will be offended.
What to insist on in the proposal
- Generation modelled against your half-hourly consumption data, with self-consumption and export shown separately
- A structural assessment of the roof and a statement on remaining covering life
- The grid connection position: application status, expected timescale, and what happens if capacity is refused or limited
- A programme with dates and dependencies
- Warranty terms for equipment and workmanship, stated separately
- What operations and maintenance is included, what it costs afterwards, and what the monitoring arrangement is
- A clear statement of what is excluded
Warning signs
- A proposal built on an annual consumption figure rather than your half-hourly data
- No structural assessment, or one done by the sales team
- The grid connection treated as a formality
- A savings figure using the commodity rate rather than your full delivered cost per unit
- A “commercial grant” referred to vaguely. Ask them to name it
- Reference to closed schemes, such as the Feed-in Tariff or Enhanced Capital Allowances. It means the material is old and probably so is everything else
- Large payments demanded up front with nothing on site
Contract points worth attention
- Liquidated damages for late completion, if the programme matters to you
- Who carries the risk if the network operator restricts or refuses capacity after you have signed
- Retention, and what triggers its release
- Roof warranty. If your roof is under warranty, does the installation void it? Check with the roof manufacturer before, not after
- What happens if you sell the building or your lease ends
That last point again: if you lease the premises, sort the landlord’s consent before you spend money on design. It stops more commercial solar projects than anything technical.