A written solar installation contract helps establish exactly what the installer and customer have agreed before work begins, including the scope of works, system specification, price, payment stages, variations, responsibilities, warranties, commissioning and handover.

For professional solar installers, a contract also creates a clear point of reference if a disagreement develops over additional work, delays, performance expectations, existing electrical systems, roof condition or payment.

A professional solar panel installation contract should clearly record the proposed system, installation scope, price and responsibilities of both installer and customer.

Important areas can include panel layout, inverter and battery specification, performance estimates, deposits, stage payments, additional works, variations, DNO requirements, G98/G99 processes, access, roof condition, existing electrics, commissioning, snagging, warranties and final handover.

The exact terms should reflect the type of solar project being undertaken rather than relying on one generic agreement for every job.

A residential solar agreement is designed for an installer working with a homeowner, while a B2B solar contract is designed for work between businesses.

Commercial solar projects often require firmer terms around milestone payments, programme dates, variations, additional works, delays, responsibility for other contractors, completion triggers, invoices and commercial liabilities.

Domestic solar agreements also need to reflect the homeowner relationship and the applicable consumer requirements surrounding residential work.

Many payment disputes begin because the parties disagree about when work was completed, whether additional work was included, whether snagging justifies withholding payment or when a payment milestone was reached.

A properly structured solar contract can establish deposits, stage payments, final payment dates, variation procedures and completion requirements before installation starts.

For commercial projects, defined payment triggers can also help reduce the risk of payment for completed solar work being delayed because of unrelated work or problems caused by another contractor.

Where relevant to the installation, a solar agreement should make responsibilities surrounding DNO notification or approval, G98 and G99 processes and grid connection requirements clear.

These processes can involve third parties and may affect project timescales, so installers should avoid creating the impression that every stage of grid connection or approval is within their direct control.

The contract supports the commercial relationship between installer and client while the installer separately follows the applicable technical, certification and regulatory requirements for the project.

A combined roof replacement and solar installation contract needs to deal with two different areas of work within the same project.

Terms can cover roof specifications, tile or slate selection, roof components, solar panels, mounting equipment, inverter and battery locations, scaffolding, hidden roof defects, variations, stage payments, commissioning and handover.

It is also important to distinguish between roofing workmanship warranties and solar installation warranties, particularly if the roof requires maintenance or the solar system is disturbed by another contractor in the future.

Responsibility should be established clearly in the original agreement.

Years after installation, a roof may require inspection, repair or maintenance while solar panels and mounting equipment remain above it. That can involve removing, disturbing and later reinstating parts of the solar installation.

A specialist roof-and-solar agreement can help define the boundaries between the original roofing work, solar installation, future maintenance and work carried out by third parties, reducing the scope for later arguments about damage, warranty responsibility or additional costs.

A solar service and maintenance agreement should explain exactly what maintenance services are included and where the contractor's responsibility ends.

This can include planned inspections, preventive maintenance, fault finding, reactive callouts, response times, access, payment, cancellations, existing system condition and customer responsibilities.

It should also distinguish maintenance work from faults connected with manufacturer warranties, previous installers, older systems or third-party interference.

Not every solar project creates the same contractual risks or responsibilities.

A standard homeowner installation differs significantly from commercial solar, off-grid systems, retrofit PV, agricultural solar, roof replacement with solar, maintenance work, battery projects, heat pump integration and EV charging.

Using a project-specific agreement allows the terms to reflect the actual work being carried out instead of forcing every installation into one generic solar contract.

Common areas of disagreement include late or withheld payment, additional works, variations, solar performance expectations, panel positioning, roof condition, existing electrical problems, DNO delays, G98/G99 processes, snagging, warranties, system handover and customer responsibilities.

Commercial projects can also involve disputes over programme delays, work carried out by other contractors, completion milestones and invoice payment.

Construction Companion's solar agreements are built around knowledge of these real industry pressure points so they can be addressed clearly before they develop into larger disputes.