Collect information without climbing onto the roof
Record roof orientation, visible shading and any known repair history from a safe position. In Ireland, a solar proposal should consider the actual site rather than a standard roof illustration. Note whether trees, neighbouring buildings or roof features create shade at different times.
Bring a picture of household demand
Gather available electricity-use information and describe when the household is normally active. Include expected changes, such as working from home, but separate them from existing use. A system proposal is easier to judge when its assumptions are visible.
Ask the installer to explain the design
Request the basis for the expected generation, treatment of shading and proposed equipment location. Ask how roof maintenance, access and future replacement have been considered. Compare proposals using the same information, and check current Irish guidance through SEAI rather than relying on outdated grant figures.
Keep documents together
Save the design, product details, warranties and commissioning information in one place. Do not treat a predicted output as guaranteed income. Before choosing a system, make sure roof condition, electrical work and any permissions have been addressed by the appropriate people.