Solar Carport vs Rooftop Solar: Which is Right For Your Site?

Per-kWp install cost

Rooftop: £700-£900/kWp turnkey. Carport: £950-£1,300/kWp turnkey. The 25-35% premium for carport reflects: structural steel (vs free rooftop), foundations and groundworks, planning permission overhead, longer DC and AC cable runs.

Annual yield

Rooftop (south-facing 30° tilt): 950-1,050 kWh/kWp/yr in UK midlands. Carport (flat or 10° tilt, bifacial): 1,000-1,200 kWh/kWp/yr — the bifacial bonus from tarmac reflection adds 5-12%.

Available area

Rooftop: limited to roof footprint (and often only ~60% of roof is usable after vents, plant, edge zones, skylights, MGA). Carport: limited to car park footprint, but typically gives more useful area than the building's roof. Many sites have 2-3× more car park area than roof area.

Structural overhead

Rooftop: requires structural survey of existing roof. Many UK commercial roofs (asbestos, lightweight membrane, old steel) cannot take PV load without strengthening. Carport: builds own structure; no constraint from existing building.

Planning

Rooftop: typically Permitted Development (Class A or J, GPDO 2015). Carport: typically requires full planning permission. Carport planning adds 8-12 weeks to project timeline.

EV integration

Rooftop: difficult — chargers go in car park, panels on roof, requiring AC cable run between them. Carport: built-in — DC stubs at column bases, cable runs are short and integral to carport design.

Visibility and brand

Rooftop: typically not visible from ground level. Carport: highly visible — visible from car park, often from street. Strong sustainability marketing surface.

Combine both

The dominant pattern for serious decarbonisation: install rooftop first (faster, cheaper), then add carport as a second phase. Net result: 2-3× more on-site solar than rooftop alone could deliver.