School solar case studies: two modelled examples
Two modelled examples that show how the sizing, value and payback work. They are not records of real installations: every figure is worked from the assumptions stated under each one, so you can rerun them with your own numbers.
A 118 kW array on a trust secondary school
A secondary school in a multi-academy trust, with a 950 sqm flat membrane roof on the main teaching block and a busy daytime IT and catering load.
- System size
- 118 kW (218 panels, 2 inverters)
- Annual generation
- 108,000 kWh
- Annual saving
- £19,900
- Payback
- 6–7.5 years
Outcome: Assumes about 70% of generation is used on site at 24.14p/kWh (DESNZ average non-domestic price, first quarter of 2026) and the rest exported at an assumed 5p/kWh; cost at this guide’s planning range of £1,000–£1,260 per kW, paid from capital.
A 55 kW array with a battery on a primary school
A community primary of around 240 pupils in a single-storey 1970s building, open in term time only.
- System size
- 55 kW (102 panels, 1 inverter, 75 kWh battery)
- Annual generation
- 50,000 kWh
- Annual saving
- £8,200
- Payback
- 7–8 years (panels)
Outcome: Assumes the battery lifts on-site use to about 60%, valued at 24.14p/kWh with an assumed 5p/kWh export rate; payback covers the panels only, at £1,000–£1,260 per kW, because there is no sourced battery price in this guide.
Every school is different. What these examples share is the method: size from at least twelve months of half-hourly meter data including a holiday period, choose the funding route that fits the school’s status (see solar panels for schools grants), schedule the disruptive works into the holidays with properly checked crews, and ask for a live-generation display for the classroom. For real, published school projects, the Great British Energy and DfE announcements on gov.uk list programme figures; see Great British Energy solar for schools.