Commercial solar · 100 kWp
100 kWp commercial solar system — cost, size and payback (UK)
A 100 kWp system suits mid-size UK businesses using 130,000–180,000 kWh a year — a 10,000–15,000 sq ft warehouse, a mid-size factory, a supermarket, a school, or a 30-room hotel. Under Permitted Development it needs no planning application, and the DNO G99 route is a standard 45-day approval.
100 kWp at a glance
System size
100 kWp
Panels
~200 panels (500 W each)
Roof area
10,000–15,000 sq ft (~930–1,400 m²)
Annual generation
~95 MWh/year (95,000 kWh)
Installed cost
£75,000–£90,000 installed
After Full Expensing
£56,250–£67,500 after Full Expensing
Annual saving
£18,000–£24,000/year
Payback
3.5–5 years after Full Expensing
Best fit business types
- Small-to-mid warehouses and distribution
- Mid-size factories with day-shift operations
- Supermarkets and larger retail
- Primary and secondary schools
- Mid-size hotels, care homes
Design and spec notes
- Two-to-three inverter setup, typically string inverters at 25–33 kW each.
- Standard G99 DNO application, 45 working days for a fitted response.
- Battery pairing (100–200 kWh) is common for retail and hospitality.
- Optical panel choice: 500–550 W N-type TOPCon.
Related reading
FAQ — 100 kWp systems
How much roof space does 100 kWp need?
About 930–1,400 m² (10,000–15,000 sq ft) of usable roof, allowing for setbacks, walkways and rooflights.
What's the payback on 100 kWp?
3.5–5 years after Full Expensing for a well-utilised site — faster on 24/7 sites, slower on part-time occupation.
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