NHS Foundation Trust acute hospital · 1.2 MWp solar + integrated decarbonisation
1.2 MWp solar PV (plus heat pumps, insulation, LED) commercial solar PV installation with combined grant + tax relief stack delivering N/A (fully grant-funded) post-tax payback on £8,400,000 gross capex.
Anonymised composite case study
Names, dates and exact financial figures have been changed to preserve client confidentiality. Project structure, funding combinations, technical configuration, and order-of-magnitude figures are real and based on completed work. Full editorial disclosure on the about page.
Project snapshot
| Sector | NHS Foundation Trust · acute hospital + 3 community sites |
| Location | Yorkshire and the Humber |
| System size | 1.2 MWp solar PV (plus heat pumps, insulation, LED) |
| Battery storage | None on solar; standby generation maintained |
| Gross project capex | £8,400,000 |
| Grant value | £8.4m (PSDS Phase 3a — 100%) |
| Year-1 tax relief | N/A (NHS body — no CT liability) |
| Net effective cost | £0 |
| Annual savings/revenue | £308,000/year (electricity import reduction) |
| Post-tax payback | N/A (fully grant-funded) |
| CO2 saving | 235 tCO2e/year (solar element) |
| Year commissioned | 2024 |
Context
The trust operates a 750-bed acute hospital plus three community hospitals across a Yorkshire metropolitan area. Annual electricity consumption: 28 GWh; gas: 42 GWh. Baseline Scope 2 emissions: 5,900 tCO2e/year. The trust's net zero plan committed to 80% Scope 1+2 reduction by 2032, in line with the NHS Green Plan deliverables.
In Q1 2021, the trust's Sustainability Director identified the upcoming PSDS Phase 3a window as the prime funding opportunity. The trust committed £180,000 of pre-application design fees to RIBA Stage 3 across the four sites — well above standard NHS pre-application investment. The application went in within 90 minutes of the Phase 3a window opening in October 2021.
The challenge
The clinical context made the project unusually constrained:
1. **Operational continuity.** Roof works on a live acute hospital had to coordinate with infection control, surgical theatre scheduling, and emergency department access. No interruption permitted.
2. **HEMS (Helicopter Emergency Medical Services) clearance.** The main hospital roof had a helipad designation. Solar panel placement had to respect HEMS approach corridors and emergency landing zones.
3. **MES (Medical Engineering Services) compliance.** HTM 06-01 standards govern hospital electrical systems. Solar integration with the existing standby generation and clinical UPS systems required specialist engineering.
4. **Listed building constraints.** The hospital's main administration block (1885 construction) was Grade II listed. Listed Building Consent was required even for ancillary mechanical works.
5. **Procurement timing.** Public Contracts Regulations 2015 required full OJEU-style tendering — 8-week minimum process for the construction contract.
Funding approach
The trust's energy team structured the programme as four phases delivered across 18 months:
**Phase 1 (months 1-4): Insulation and fabric.** Cavity wall insulation, loft insulation, double-glazing on the 1960s-built clinical wings. Pre-requisite for heat pump performance.
**Phase 2 (months 5-9): Heat pump installation.** 4 × 500kW air-source heat pumps replacing the existing gas-fired CHP. Required substantial DNO upgrade and HV switchgear installation.
**Phase 3 (months 10-14): Solar PV.** 1.2 MWp across the main hospital roof and two outlying buildings. Approximately 3,000 panels.
**Phase 4 (months 15-18): LED + BMS.** LED retrofit across 18,000 m² of clinical space. Building Management System upgrade with carbon reporting capability.
Funding stack:
- **PSDS Phase 3a grant:** £8.4m (100% of qualifying capex) - **Internal trust capital:** £400,000 for non-eligible elements (helipad re-marking, HTM-compliant clinical UPS integration) - **Salix Recycling Fund:** £180,000 at 0% interest for non-PSDS-eligible BMS upgrade - **Total programme cost:** £8.98m
Outcome & performance
The programme completed in Q2 2024, two months ahead of schedule. Year-one performance (12 months post-commissioning):
- **Annual generation:** 1.1m kWh from solar (vs 1.0m modelled) - **Self-consumption:** 98% (24/7 hospital load) - **Annual electricity import reduction:** £308,000/year (at 28p/kWh blended commercial rate) - **Heat pump performance:** COP 3.4 average across the seasons - **Combined annual energy savings:** £1.4m across the full programme - **CO2 saving:** 1,520 tCO2e/year (solar 235 + heat pump 1,280 + LED 70) - **Scope 2 reduction:** 26% from baseline
The trust completed the wider Phase 3a programme on time and is preparing a follow-on Phase 5 application for additional sites — including the remaining community hospital and the trust's largest GP polyclinic.
Lessons learned
- PSDS application preparation must start 12-18 months before the window opens. The £180k pre-application investment was decisive.
- Integrated heat pump + solar + insulation packages score materially better than solar-only applications. Solar was 12% of total capex but enabled the 88% balance.
- Hospital roof works require detailed clinical engagement — not just facilities management. Theatre scheduling, infection control, HEMS clearance all material.
- HTM 06-01 hospital electrical standards add cost and time but are non-negotiable. Specialist commissioning engineers essential.
- PSDS funding is paid in arrears against milestones. Trust capital must front the full project cost during delivery (recovered over 6-18 months as milestones verify).
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