Commercial Solar Feasibility Study and Site Survey: What Each Covers
Updated 23 October 2026 · SEO Dons Editorial
What is the difference between a feasibility study and a site survey?
A feasibility study is done at a desk, from documents. A site survey is done on the building. The first decides whether the second is worth doing, and the second decides whether a design can actually be built. This guide is published information and does not carry out either. The installation guide sets out the whole project programme; this page goes deeper on the evidence behind the first two stages.
| Stage | Main inputs | Main outputs | Decision it supports |
|---|---|---|---|
| Desk feasibility | Bills or half-hourly data, address, roof drawings or imagery | Size band, outline yield and payback, first view of the connection | Whether to spend on a survey |
| Site survey | Roof, plant room and switchroom access, building records | Findings on structure, roof life, fragile areas, asbestos, intake and cable routes | Whether and how a design can be built |
| Specialist follow-ons | Structural engineer, asbestos surveyor, network operator | Appraisal, survey report, connection offer | Programme and any change of scope |
Before any visit, settle in writing whether a study is part of a quote or a separate commission, and what you receive at the end of it.
What should a desk feasibility study show you?
Use the output as a test of the study. A useful one states:
- which consumption data it used, and how much of the load falls in daylight hours and at weekends;
- the usable roof area after setbacks, rooflights and plant, with a layout sketch;
- the yield model and its assumptions, which you can cross-check against PVGIS in the way the quote comparison guide describes;
- which network operator serves the site, the connection route it assumes and a first view of capacity;
- an outline payback with its assumptions, and the conditions under which the answer would be no.
Network capacity deserves care at this stage. Electricity North West, for example, publishes a heatmap tool and tells developers to look at it before applying, but says it cannot replicate the accuracy of the detailed assessment in the formal application, so it advises talking to it first. The guide to network capacity heat maps explains how to read them. A study that never mentions the network operator is incomplete.
Which documents should the business gather first?
| Document | Why it matters |
|---|---|
| Twelve months of bills, and half-hourly data if the meter records it | Sets the size band and how much generation the building can use |
| The MPAN from a bill | MCS says the first two digits correspond to a network operator, and ENA's search finds the operator from a postcode |
| Roof drawings, structural information, as-built details | Lets a structural engineer assess loads and fixings |
| Roof covering records and warranty | Shows remaining life and what fixing methods the roof warranty tolerates |
| Asbestos register and survey reports | HSE says asbestos information should reach contractors early, for example when a quote is requested |
| Single-line diagram, board schedules, spare capacity | Decides where and how the system connects |
| Health and safety file or records of earlier works | Part of the pre-construction information the client must provide |
| Lease, landlord consent route, insurer requirements | Consent and insurance can outlast the design in the programme |
| Planning constraints such as listing or conservation area | The planning guide covers the route in England |
| Site rules: roof permits, working hours, shutdown windows | Feeds the programme and the safe-access plan |
CDM 2015 defines pre-construction information as information in the client's possession, or reasonably obtainable by or on behalf of the client, that is relevant to the construction work. Collecting these documents is the start of that duty, and the CDM client duties guide covers the rest.
What changes on a leased building?
Several parties can have a stake in the same project: the landlord, the tenant and, under a power purchase agreement, the funder. CDM 2015 recognises this. Where there is more than one client, one or more of them may agree in writing to be treated as the only client, although the regulations still leave every client with duties to cooperate and to pass on information they hold. Settle early who gives roof access, who holds the asbestos register and drawings, and who signs consent, because a survey needs all three.
What does a site survey check that a desk study cannot?
The roof as a place to work. 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, liner panels and corroded metal sheets among those likely to be fragile. It also says falls through fragile surfaces, particularly fibre-cement roofs and rooflights, account for 22% of all fall from height fatal injuries in construction. A survey should map fragile areas and rooflights, even those hidden by paint or hard to see in some light.
Asbestos. HSE says to assume a building built or refurbished before 2000 contains asbestos, and that installation work which disturbs the fabric where asbestos could be hidden needs a more intrusive survey before work starts. A refurbishment or demolition survey must be carried out by a competent surveyor, is destructive, and means the area must be vacated during the survey. HSE strongly recommends accredited asbestos surveying organisations.
Structure, intake and access. The survey records the roof structure and fixings for the engineer, the switchroom, board capacity and cable routes, and the access, laydown and lifting arrangements. The RC62 fire safety guide covers what insurers look for, which the survey should record: roof build-up, compartment walls and DC cable routes.
The standard it follows. MCS publishes MIS 3002, which outlines requirements for the design and installation of solar PV systems, but MCS certification stops at 50 kW for electrical systems. For a larger array the contract should say what the survey will cover and what procedure it follows.
How should the survey visit itself be managed?
HSE says all work on roofs is highly dangerous, even if a job only takes a few minutes, and that on business premises contractors should work closely with the client and agree arrangements for managing the work. Ask for a method statement for the visit, including how the surveyor will reach and move across the roof, and name a contact who can open the plant room and switchroom. Tell the surveyor about any known fragile areas before arrival.
How do you use the findings?
Treat the survey as a gate with three outcomes: proceed, re-scope, or stop. Re-scoping is common and is not a failure: an array limited to the strongest bays, a mounting change, or a roof repair first. Feed the findings back to every bidder so that quotes still compare, using the comparison table. When the documents are ready, you can send an enquiry through the quote form.
Sources
- Health and Safety Executive: Roof work; Fragile surfaces; Arrange an asbestos survey; Find out if asbestos could be present; Provide information to anyone who might disturb asbestos, checked 22 October 2026.
- legislation.gov.uk: CDM Regulations 2015, regulation 2; regulation 4, checked 22 October 2026.
- MCS: Notifying DNOs; Standards and tools library; Becoming certified, checked 22 October 2026.
- Energy Networks Association: Who's my network operator?, checked 22 October 2026.
- Electricity North West: Heatmap tool (an operator page, used only for facts about that operator), checked 22 October 2026.
- European Commission Joint Research Centre: PVGIS user manual, checked 22 October 2026.
Common questions
Do I need a site survey before I can get a quote?
Not always. A desk feasibility can support an indicative figure, but a design to build from needs the survey findings. Ask each bidder to list the assumptions the survey must confirm, such as roof strength, asbestos and board capacity, so you know what could change.
Is a feasibility study the same as a design?
No. It tests whether solar suits the building and gives a size band and outline numbers. A design fixes the layout, strings, protection and connection details. Treat figures in a feasibility study as indicative until the survey and the network operator's response are in.
What changes if the building was built before 2000?
HSE says to assume asbestos is present in a building built or refurbished before 2000. Any installation work that disturbs the fabric where it could be hidden needs a more intrusive survey first. Share the asbestos register with bidders early so that survey time and method are planned rather than discovered.
Who should be present on the survey day?
Someone who can authorise roof access and open the plant room and switchroom, ideally the person who knows the building's electrical layout. On a leased building the landlord's representative may also need to attend. Agree the method statement and any restricted areas beforehand.