UK businesses considering commercial solar often ask the same question: should we put panels on the roof, or build a canopy over the car park? The answer depends on your roof condition, car park size, planning context, and budget — but for many commercial properties, a solar canopy is now the smarter choice.
The Core Trade-Off
Rooftop solar uses existing structure, so structural costs are lower. But roofs are often partially shaded, face the wrong direction, have limited usable area, and require access constraints for maintenance. Roof condition is also a risk — a 25-year solar system on a roof that needs replacement in 8 years means removing and reinstalling the array.
Solar canopies require a new structure (higher upfront cost) but offer better panel orientation, bifacial gain from reflected light below, no roof access issues, EV charging integration, and covered parking as a user benefit. The site is the car park — which is already owned, already paved, and unlikely to need major works that conflict with the solar.
Cost Comparison
| Rooftop Solar | Solar Canopy | |
|---|---|---|
| Structural cost | Minimal (existing roof) | £120-£280/sqm of canopy |
| Total installed cost/kWp | £700-£900 | £800-£1,100 |
| Useful life | 25-30 years (panel) but limited by roof life | 30-40 years (hot-dip galvanised steel) |
| EV integration | Requires separate cable run | Designed in from day one |
| Covered parking | No | Yes |
| Planning complexity | Usually lower | Higher in England — prior approval needed |
| Roof condition dependency | High | None |
Planning is one of the genuine differences. A roof array on a business building uses a different permitted development right, while a car park canopy in England relies on Class OA, which requires a prior approval application on siting, design, appearance and glare before work starts — the limits are set out in our guide to planning permission for solar carports.
When Rooftop Solar Wins
- Your roof is in excellent condition and has 20+ years remaining life
- You have a large, unshaded south-facing roof area
- Your car park is small or not well oriented
- Budget is constrained and capital cost is the primary concern
When Canopy Solar Wins
- Your car park has 40+ spaces (above this threshold the canopy economics improve significantly)
- Your roof has asbestos cement cladding that cannot take additional load (very common in pre-2000 industrial buildings)
- You run a school whose roof is in poor condition — the Department for Education will not approve a solar PPA case on a poor roof, which is one reason solar PV school canopies are on the table
- You want EV charging integrated into the system
- Your roof faces east-west (two-slope roofs lose 15-20% yield versus a south-facing canopy)
- You want covered parking as a user amenity
- Your tenants or building users have EVs and want to charge at work
Yield Comparison
A 100 kWp south-facing rooftop in central England: approximately 92,000-95,000 kWh/year.
A 100 kWp south-facing canopy in the same location: approximately 96,000-102,000 kWh/year (bifacial gain from reflected light adds 5-8%).
The canopy yield advantage is modest but real. More significant is the EV integration value — which can add 30-60% to the effective economic return when EV chargers are included.
The Combined Strategy
For many commercial properties, the answer is both: rooftop solar on the south-facing parts of the roof that are in good condition, and a canopy over the car park. The two systems share a grid connection and energy management controller.
Combined roof + canopy projects make sense where the total system size is 300-600 kWp across both surfaces — too large for the roof alone, too expensive to deliver just on the canopy. The combined approach also provides redundancy: if one system needs maintenance, the other continues generating.
Summary: Which Should You Choose?
Ask yourself:
- Is my roof in good condition and likely to last 25 years? If no, canopy.
- Do I have 40+ parking spaces? If yes, canopy economics likely win.
- Do I want EV charging now or in the next 5 years? If yes, canopy integrates it better.
- Is my roof north-facing or heavily shaded? If yes, canopy.
- Is initial capital cost my primary constraint? If yes, rooftop is likely cheaper.
If you answer ‘yes’ to 2 or more of questions 1-4, a canopy is likely your best option. Get quotes for both and compare the 25-year IRR — not just the upfront cost.
Our car park solar canopy page sets out the per-bay figures behind this comparison. For the engineering detail behind those numbers, see our guide to single-post canopies.