Commercial solar survey checklist: what to prepare

The short answer

Before a commercial solar survey, try to gather:

• 12 months of electricity bills and, ideally, half-hourly consumption data
• your MPAN (the supply number on the bill) and your agreed supply capacity
• roof drawings, plus the roof's age, covering and repair history
• the asbestos register, if the building is old enough to need one
• your lease and any landlord consent, if you do not own the freehold
• anything you know about planning constraints on the site
• your buildings insurer's details
• a clear idea of who makes the decision and how it might be paid for

None of this is needed to start the conversation. A few recent bills and a rough idea of when the roof was last replaced are enough to request a free survey, and you can fill the gaps as you go. Each extra item removes a guess from the design, so the proposal you get back is easier to trust.

Why preparation changes the result

A survey turns a building and an electricity bill into a system design, a generation estimate and a financial case. Where information is missing, the installer has to assume, and assumptions can be too cautious in one place and too optimistic in another. Good information narrows the range of outcomes. For a full picture of each part of the process, see what the survey includes.

Three questions decide most commercial solar projects:

1. How much electricity do you use while the sun is up? This sets how much generation you use on site, which is worth far more than electricity you export.
2. Can the roof carry panels for 25 years or more without major work? A roof that needs replacing in five years changes the plan completely.
3. Can the local network accept the system? This decides the size you can connect, how long approval takes and whether export needs to be limited.

Almost everything on the checklist below feeds one of those three questions.

Energy data

Electricity bills

Collect 12 months of bills for every meter that serves the building, not just the main one. The useful parts are the unit rates (single rate, day and night, or more time bands), standing charges, any capacity or availability charges, and the contract end date. The contract end date matters because the value of solar depends on the price you would otherwise pay, and a renewal can move that price significantly in either direction. If you are on a flexible or pass-through contract, say so, because the financial model should reflect it.

Half-hourly consumption data

If your site has a half-hourly or smart meter, your supplier, meter operator or energy broker can usually provide a download of consumption in 30 minute periods, normally as a spreadsheet. Ask for at least the last 12 months.

This is the single most valuable item on the list. It shows your weekday and weekend pattern, shift start and finish times, the overnight baseload from refrigeration, servers or compressed air, and how use changes between summer and winter. Laying the expected solar generation curve over that profile is how a designer estimates the share you will use on site. Our page on energy data analysis explains how the data is used.

If you do not have half-hourly data, monthly meter readings plus a plain description of operating hours still help. On some sites the installer may suggest a temporary logger.

MPAN and supply capacity

The MPAN (meter point administration number) is printed on your electricity bill, usually in a box marked with an S. It identifies your supply point and the distribution network it sits on. Please send the full number for each supply.

Supply capacity is the maximum your connection is designed to take. On larger supplies it often appears on the bill as an agreed or authorised capacity in kVA. Photos of the incoming supply, main switchboard and any transformer help the installer judge whether the electrical infrastructure can take a solar connection. Systems above the small-system limits need approval from the network operator under G99, covered on our page about G99 and DNO applications.

The roof and the building

Roof drawings

Useful drawings include roof plans, elevations, sections and any structural calculations from when the building was designed or extended. Building handover files and O&M manuals often contain them. If none exist, the surveyor can measure the roof, use aerial imagery or fly a drone, but drawings save time and help when a structural engineer is needed later.

Roof age, covering and condition

Note when the building was constructed, when the roof was last replaced or overclad, what the covering is (profiled metal, fibre cement, membrane, felt, tiles or slate), and whether any roof warranty is still running. List known leaks, repairs and rooflights.

The practical test is simple: if the roof is likely to need replacing during the life of the panels, it is usually better to deal with it first, because removing and refitting an array later adds cost and downtime. Read more about roof surveys for solar.

Asbestos register

The Control of Asbestos Regulations 2012 place a duty to manage asbestos in non-domestic premises. If your building was built or refurbished before 2000, there is a real chance some materials contain asbestos, and fibre cement roof sheets are a common example. Have your asbestos register or management survey ready. Before work on the roof, a more intrusive refurbishment survey of the affected area may be needed. Our page on asbestos roofs covers the options, from working around sound sheets to replacing the roof.

Access and site rules

Tell the surveyor about access routes, roof access points, permits to work, inductions, PPE, working hours and any areas with hygiene or security controls. Sites with live forklift traffic, food production or public access need this planned in advance.

Legal, planning and insurance

Ownership, lease and landlord consent

If you own the freehold, say so. If you lease the building, check:

• whether the lease allows alterations to the roof and electrical installation, and on what terms
• whether the landlord's written consent is needed, and who to ask
• how many years remain on the lease compared with the expected payback period
• what happens to the panels at the end of the lease, including any reinstatement or dilapidations obligations

Landlords installing on let buildings have their own set of questions, covered on our commercial landlords page.

Planning constraints

Most rooftop solar on commercial buildings in England can proceed under permitted development, but conditions apply. Tell the surveyor if the building is listed, in a conservation area or other protected land, or subject to planning conditions or an Article 4 direction. Scotland, Wales and Northern Ireland have separate rules. Our guide to commercial solar planning permission sets out the main points.

Insurance

Note your buildings insurer and policy details. Most insurers expect to be told about a rooftop PV installation, and many refer to RC62, the fire safety recommendations for rooftop PV on commercial buildings. Raising it early avoids a design that the insurer later asks to change.

Decisions and budget

A survey goes better when the right people are involved from the start. Before the visit, agree:

• Who signs off. An owner, finance director, board, governors or trustees. Find out what they will want to see in a proposal.
• How it might be paid for. Outright purchase, asset finance or leasing, or a power purchase agreement where a third party owns the system. Each changes the proposal you need. Our finance pages cover the options.
• What matters most. Lower bills, carbon reporting, protection from price rises, preparing for EV charging or a combination. Rank them.
• Timing drivers. An energy contract renewal, planned roof works, a financial year end, or a tenant moving in or out.

The checklist

Use this as a working list. Tick off what you have and note what you are chasing.

Energy and supply

• 12 months of electricity bills for every meter on the site
• Half-hourly consumption data for the last 12 months (or monthly readings)
• MPAN for each supply
• Agreed supply capacity in kVA, if shown on the bill
• Current energy contract end date and type
• Photos of the incoming supply, main switchboard and any transformer
• Notes on planned changes in use: new machinery, EV charging, heat pumps, extra shifts

Roof and building

• Roof plans, elevations, sections and structural calculations, if available
• Year built and year of last roof replacement or overclad
• Roof covering type and any remaining roof warranty
• Known leaks, repairs, rooflights and roof plant
• Asbestos register or management survey (buildings built or refurbished before 2000)
• Roof access points, site rules, permits and induction requirements

Legal and planning

• Freehold title, or lease with the alterations and reinstatement clauses marked
• Landlord contact and any consent already given
• Listed status, conservation area or other designations
• Planning conditions on the building that might be relevant

Insurance and safety

• Buildings insurer name and policy number
• Any insurer requirements already raised for roof works or PV
• Current fire risk assessment

Decisions

• Named decision maker and the evidence they need
• Preferred funding route, or a list of routes to compare
• Ranked objectives
• Dates that drive timing

What happens on the day

For an in-person survey, a site contact meets the surveyor, who will usually:

• walk the site and confirm which buildings and roofs are candidates
• inspect the roof from a safe position, using ladders with edge protection, a mobile elevating work platform or a drone, depending on the building
• record the covering, fixings, condition, rooflights, plant and shading
• look at the structure from inside where possible, noting purlins, rafters or trusses
• inspect the electrical intake and switchgear, and identify where inverters could go
• trace likely cable routes and possible locations for battery storage or EV chargers
• photograph everything for the design team

The time needed depends on the number of roofs, the access arrangements and the electrical layout. A virtual survey uses aerial imagery, your photos and drawings, and a video call instead, and can be a sensible first step where the site is straightforward.

What happens after

The installer uses the survey findings and your data to prepare a proposal. A complete proposal normally includes:

• a layout drawing and the system size in kWp
• an estimated annual generation figure with its assumptions stated
• an estimate of how much will be used on site and how much exported, based on your data
• the financial case under the funding routes you asked about
• any further work needed first, such as a structural assessment, asbestos survey or roof repair
• the expected route and timescale for network approval
• a quotation, with what is and is not included

Check the proposal against our guide to choosing a commercial solar installer, which explains how to test the assumptions. There is no obligation to go ahead.