What your solar quote should include

With two or three quotes in front of you, the useful comparison is line by line. This is what the lines should be.

The system

• Panels — make, model, number of them, and the total size in kW.
• Inverter — make and model, and whether it is one inverter or one per panel.
• Battery — if included, make, model and usable capacity.
• Mounting — the rails and attachments, and how they fix to your roof.

The work

• Electrical — the run from the array to your panel, and any disconnects.
• Service panel — whether yours is adequate, and the cost if it is not. This is the single most common difference between two quotes.
• Roof work — anything that has to happen before panels go on.

The paperwork

• Permit — the application to your building department, and its fee.
• Inspection — the sign-off, and what happens if it fails.
• Utility interconnection — the application to connect to the grid.
• Safety labels and placards — required by the electrical code, supplied by the installer.

The terms

• Warranty — separately for panels, inverter and the installation itself. These are three different lengths from three different parties.
• What is excluded — in writing.
• Timescale — including how long the permit is expected to take, which is the part nobody controls.