180 kW + Battery Install — South Coast Sixth Form College
- System size
- 180 kW + 80 kWh battery
- Annual saving
- £39,000
- Payback
- 6.2 years
- Location
- South Coast
Scenario
A standalone sixth form college on the south coast with 1,400 learners and a 12,000 sqm urban campus faced an electricity bill that had risen from £165,000 in 2022 to £315,000 in 2025 against frozen 16-19 base funding rates. A new principal arrived in autumn 2024 with sustainability and operational cost reduction equally prioritised on the senior leadership scorecard. The corporation board approved a Climate Action Plan in early 2025 aligned with the AoC Climate Action Roadmap, committing to a 40% scope-2 reduction by 2030.
The Sustainability Lead — a senior maths teacher who had taken on the role alongside teaching commitments — built the internal case for solar. We were appointed in May 2025 after a competitive feasibility tender.
What we delivered
- System size: 180 kW total — 110 kW on the main teaching block, 70 kW on the science block
- Panel count: 330 × 545 W panels (Trina Vertex S+)
- Inverters: 2 × Sungrow 75 kW string inverters (one per building, identical for monitoring simplicity)
- Battery storage: 80 kWh in main plant room (LiFePO4 chemistry, GivEnergy commercial)
- Monitoring: Live-generation dashboard in main entrance + classroom data feed for environmental science
The main teaching block is a 4,200 sqm membrane roof on 16° standing seam, south-east aspect, minimal shading. The science block is 2,800 sqm pitched concrete tile, south aspect with some morning shading from a 4-storey adjacent building (modelled into the design — 7% generation loss accepted in exchange for the cleanest roof slope).
Funding
100% Salix Decarbonisation Loan — single application, single corporation board approval.
- Capital cost: £170,000 at £945/kW (single-site mid-scale unit cost)
- Loan term: 8 years
- Annual repayment: £21,250
- Modelled annual energy savings: £39,000 (driven by the 80 kWh battery shifting weekend and summer-holiday generation into term-time use)
- Net cash-flow positive year one: £17,750/year
Salix application written by our team; the college’s Director of Finance reviewed and signed in under 30 minutes. Application-to-loan-offer turnaround: 9 weeks.
Programme
Installation phased across the summer 2025 break:
- Week 1-2: Scaffold erection across both buildings, ridge protection, edge protection
- Week 3-5: Mounting rail install, panel delivery and lifting, electrical first fix
- Week 6: Inverter commissioning, battery commissioning, monitoring system integration
- Week 7: G99 commissioning visit from the DNO, final witness testing
- Week 8: Live-generation dashboard install, classroom data feed configuration, AoC Climate Action Plan evidence pack delivery
Commissioned for the start of the autumn term 2025. The principal demonstrated the dashboard at the September open evening.
Compliance
- Listed Building Consent not required (modern campus, no listed structures)
- Asbestos R&D survey — clear on both buildings (1990s and 2005 construction)
- KCSIE 2025 safeguarding induction by the Sustainability Lead and Director of Estates
- Structural engineer survey on both roof slopes; both passed for ballast-free rail-mounted system
- G99 DNO application — accepted in 13 weeks
- ESFA Post-16 Audit Code — energy savings calculation auditable
Outcomes
- Year one actual generation: 167,200 kWh versus modelled 164,000 kWh (+2.0%)
- Year one actual energy savings: £40,800 versus modelled £39,000 (+4.6%)
- Featured as compliance-evidence case study in the college’s first AoC Climate Action Plan progress update, published November 2025
- A-level Environmental Science cohort (n=42) designed a year-long monitoring project around the install — analysing daily, weekly, and seasonal generation patterns as part of their independent study unit
- Press coverage in the local FE Week regional digest, plus a feature in the corporation’s autumn newsletter
- Open evening footfall up 18% year-on-year — the principal credited the visible sustainability commitment in parent feedback forms
What the Sustainability Lead said
“I was given the role with no extra capacity — half a day a week, alongside a full timetable. I needed an intervention that was visible, defensible to the board, and not going to consume the next two years of my attention. Solar ticked all three boxes. The build crew managed the corporation board paper, the DNO application, the structural survey, and the AoC Climate Action Plan evidence pack. My job was three meetings and one site walk.”