A solar survey should consider much more than compass direction. Roof condition, usable area, shading, structure, electrical connection and planning restrictions all affect the design.

1. Direction and pitch

An unshaded south-facing roof usually gives the highest annual output. East and west can still be useful, spreading generation across morning and afternoon. A competent proposal should show the effect of orientation and pitch on predicted annual generation.

2. Shading

• Trees and nearby buildings
• Chimneys, dormers and roof vents
• Seasonal shadows at low winter sun angles
• Future tree growth

Ask for a site-specific shading assessment. Optimisers or microinverters can help in some designs, but should not be added automatically where shading is negligible.

3. Roof condition and structure

Panels may remain for decades. Repair or replace a roof that is nearing the end of its life before installation where practical. The installer should assess loading, fixing points, wind exposure and the condition of tiles, slates or roof covering.

4. Usable space

Energy Saving Trust says a typical 3.5 kWp system may use six to twelve panels and around 10–20 m² of roof area. Actual space depends on panel dimensions, access zones, roof shape and obstructions.

5. Planning and permissions

Domestic roof-mounted solar is often permitted development, but conditions and national rules differ. Listed buildings, conservation areas, scheduled monuments, prominent locations and flat roofs may need extra checks. Ask your local planning authority where there is doubt.

6. Electrical and grid checks

The installer should check the consumer unit, earthing, cable routes, meter position and Distribution Network Operator requirements. Larger or constrained connections may need approval before installation.

Roof survey checklist

1. Photographs and measured roof dimensions
2. Orientation, pitch and shading assessment
3. Roof-covering and structural condition
4. Panel layout with obstructions shown
5. Scaffolding and safe-access plan
6. Annual generation estimate and losses
7. Planning and DNO responsibilities

Independent sources

Energy Saving Trust: solar panels · Planning Portal: solar panels