The Commercial Solar Site Survey: What It Checks and What You Get

What a commercial solar site survey is

A survey turns "could solar work here?" into a design and a price for your site. It is not a sales visit with a brochure: the installer has to check things that decide whether the system is safe, whether it will connect, and whether it will pay for itself.

It is also not a structural engineer's report on its own. Where the roof needs one, the installer arranges it, because MCS's installation standard requires the roof structure to be checked by a competent person and a qualified structural engineer to be consulted when the roof is unusual or there is any doubt (MIS 3002, section 3.9).

What we look at before anyone visits

A member of our UK team calls you first, so nobody's time is wasted:

• Ownership or landlord consent. Panels are fixed to the building or land, so we check you own it, or rent it and your landlord is willing to agree.
• Your energy spend. Roughly what the business spends on electricity and when it uses most of it.
• Roof or land. Whether there is a roof in reasonable condition, or spare land, with room for panels.
• Your electricity supply. Whether the site has a supply suited to the size of system.

Then we match the site with one MCS certified installer that covers your area and the size of job. You can check any installer on MCS's own register (MCS).

On the day: roof, structure, electrics and grid

• The roof or land. Size, pitch, orientation, condition and remaining life, and what trees, plant or nearby buildings shade it.
• Roof warranties. If the roof covering is still under warranty, MCS says the warranty provider should be consulted to find out whether the installation would invalidate it (MIS 3002, 3.9.2).
• Safe access. HSE says all roofs, once fixed, should be treated as fragile until a competent person has confirmed they are not, and lists fibre-cement sheets, rooflights and corroded metal sheets among the materials likely to be fragile (HSE). The installer plans scaffolding, edge protection and how to keep people off fragile areas.
• Asbestos. HSE's rule of thumb is to assume a building built or refurbished before 2000 contains asbestos (HSE). Older fibre cement roofs often do; see solar on an asbestos roof.
• The electrics and the grid. The supply, the main switchboard and the cable route from the panels. Most business systems are above 16A per phase, which means a G99 application to the network operator before connection (NGED); smaller ones are connected and notified within 28 days under G98 (NGED).
• How you use power. Your bills or half-hourly data show how much you use in daylight, on which days and in which months.

Roof loading and structural checks

Panels, mounting and, on flat roofs, ballast add weight and wind loads to the roof. MIS 3002 sets out what the installer has to do (MIS 3002, section 3.9):

• Every roof. The structure is checked by a suitably competent person to make sure it can take the loads of the system.
• Unusual roofs. A qualified structural engineer is consulted, for example where the roof shows signs of structural distress, has been altered, or is particularly shallow.
• Flat roofs, fixed systems. A condition survey and pull-out tests where the system is fixed to a solid deck such as concrete.
• Flat roofs, ballasted systems. A qualified structural engineer confirms the roof can carry both the system and the ballast, and the wind calculation follows recognised data.

MIS 3002 covers systems up to 50 kWp; on larger systems ask the installer how the same checks are done.

What you get afterwards

A written proposal from the installer. A good one sets out:

• The system. Size in kWp, the panels, inverters, mounting and any battery, and where it all goes.
• The numbers. Expected yearly generation, how much of it the installer expects you to use, the saving and the payback.
• The price. What it includes and excludes, such as scaffolding, roof work or the network operator's charges.
• The connection. Whether a G99 application or export limitation is needed, and the likely timetable.
• Warranties. On the equipment and the workmanship.

You can take your time over it and ask questions. Whether you go ahead is up to you. To compare it, see choosing a commercial solar installer and commercial solar payback.

How to prepare

• A recent bill. And 12 months of half-hourly data if your supplier provides it; ask them for it before the visit.
• Roof information. Drawings, the building's age, any roof warranty and any recent repairs.
• Your asbestos register. For a building built or refurbished before 2000.
• Access. Who can show the installer the roof, the plant room and the main switchboard.
• Your landlord. If you rent, their details, or their agreement in principle.