What should a commercial solar proposal include?

A useful commercial solar proposal should let you compare the design, financial case, risks and responsibilities without filling in missing details yourself. It should show how the system fits the building’s electricity use, roof, electrical infrastructure and operating plans.

How the design matches the building

The proposal should identify the roof areas being used, panel layout, orientation, pitch and any shading from nearby buildings, trees or plant. It should explain whether the design uses one roof face or several, and whether different roof areas need separate electrical controls.

Roof space alone does not determine the right system size. A good proposal compares the proposed output with the building’s daytime demand. A warehouse, office, workshop, farm building and retail unit can use electricity in very different ways. The proposal should state how much of the solar generation is expected to be used on site and how much may be exported.

Ask for a drawing showing panel positions, access routes, inverters, isolators, cable runs and any battery location. This makes practical issues visible before work starts. It also helps you check that rooflights, vents, gutters, fire routes and maintenance access have not been overlooked.

The information behind the forecast

Generation estimates should come from the actual roof and location, not a standard figure for a notional building. The proposal should state the assumed panel arrangement, system losses, shading, inverter operation and any limits imposed by the grid connection.

Electricity-use assumptions matter just as much. A proposal based only on an annual bill may miss the difference between weekday and weekend demand, seasonal production and periods when the premises are unoccupied. Half-hourly consumption data can show when the building uses power and whether a battery could shift surplus generation to a more useful time.

Look for a clear explanation of what happens if demand changes. New machinery, refrigeration, heat pumps, electric vehicles, extended opening hours or a change of tenant can alter the financial case. The proposal should identify these assumptions rather than presenting the forecast as fixed.

Costs should be separated clearly

The price should show the main equipment, design work, installation, access equipment, electrical alterations, testing and commissioning as separate elements where possible. It should also identify items that may be chargeable if the survey finds a problem, such as roof repairs, asbestos management, structural strengthening or a service upgrade.

Check whether the quoted figure includes scaffolding, welfare arrangements, permits, monitoring setup, grid-connection work and the removal of packaging or redundant equipment. If another contractor must complete part of the work, the proposal should say who is responsible and when that work must take place.

Payment stages and the point at which the contract becomes binding should be stated in plain language. A written quotation before work starts gives you a record of what has been included. It should also set out how changes are agreed, so additional work does not appear unexpectedly at the end.

The financial case needs more than a payback figure

A credible proposal should show the calculation behind its return estimate. That normally includes the expected on-site use of solar electricity, the value assigned to exported electricity, electricity-price assumptions, system costs and any battery operation assumptions.

Export income depends on the arrangement with the electricity supplier and the system’s metering and certification. MCS certification allows an eligible installation to apply for the Smart Export Guarantee, but the proposal should not treat an export tariff as a guaranteed fixed income. Tariffs and terms can change, so the assumptions and date of the calculation should be recorded.

If the proposal includes a battery, it should explain what the battery is intended to do. It may store excess solar for later use, help manage demand or reduce electricity bought at expensive times. The figures should show whether the financial model depends on importing electricity to charge the battery, and should account for usable capacity, charging losses and battery degradation.

For a business, the right decision may involve more than payback. The proposal can also help you consider budget limits, lease arrangements, planned relocation, operating costs, carbon reporting and the likely period for which the building will remain in use.

Technical and compliance responsibilities

The proposal should explain how the existing electrical installation will be assessed. The main distribution board, protection, earthing, cable routes and available capacity may need attention before solar equipment can be connected. A large commercial array may also require network approval, export limitation equipment or a change to the connection arrangement.

Planning, building control, fire safety and access requirements should be considered for the particular building. The proposal should name any approval that is still outstanding and state who will submit applications, provide drawings and respond to queries. It should not describe approval as automatic where the building, roof or site has unusual constraints.

Roof condition deserves its own written finding. If the covering is near the end of its serviceable life, removing panels later can add cost and disruption. The proposal should record what the survey has and has not checked, and identify any recommended repairs before installation.

Commercial premises may need a method statement, risk assessment, site induction, isolation plan and arrangements to protect staff, visitors and other contractors. If the building must remain in use, the proposal should explain how deliveries, roof access, shutdowns, noise and working areas will be managed.

Warranties and after-installation responsibility

Several different protections may apply, and a proposal should distinguish between them. These can include the panel and inverter manufacturer warranties, battery warranty where relevant, workmanship cover and any performance warranty. Each should state its duration, exclusions and the process for making a claim.

Ask who deals with a fault first. The proposal should say whether you contact the installer, the manufacturer or a monitoring provider, and what information will be needed. It should also explain what happens if one component fails while the rest of the system continues to operate.

Monitoring should be set up in the business’s name, with the appropriate users given access. The handover should include passwords, operating instructions, isolation information, as-built drawings, certificates and records of test results. A property manager should be able to pass this information to a new tenant, contractor or future buyer.

Maintenance requirements should be practical rather than vague. The proposal should identify inspection intervals, monitoring checks, cleaning assumptions, vegetation management and any access equipment needed. Solar systems have few moving parts, but faults can remain unnoticed without suitable monitoring.

What to look for before accepting the proposal

• The roof areas, panel layout and cable routes are shown clearly.
• The forecast explains both electricity-use and generation assumptions.
• Self-consumption, export and battery operation are treated separately.
• Included work, exclusions and possible additional costs are listed.
• Grid, planning, building and fire-safety responsibilities have named owners.
• Roof condition and any required repairs are recorded.
• Warranties cover equipment and workmanship, with claims routes explained.
• Monitoring, certificates, drawings and handover documents are included.
• The installation method suits the building’s normal operations.

For a commercial property, we prepare the proposal around the building’s use, roof and electrical records rather than applying a standard package. Where solar, battery storage or electrical alterations are being considered together, that joined-up assessment can prevent a system being designed around only one part of the site.