County General Hospital: 350kWp Yorkshire NHS PSDS
Case study: 350kWp NHS Yorkshire. PSDS Phase 3b funded 100% of eligible capex. 62% energy cost reduction across 8 buildings.
The site
A Yorkshire NHS Foundation Trust acute hospital, approximately 38,000 m² total estate, with a substantial gas-fired heating system serving outpatient and admin blocks. Annual electricity demand was 4.8 GWh; annual gas demand was 9.2 GWh.
The brief
The trust’s estates director had been progressively scoping decarbonisation since 2021. PSDS Phase 3b was the target funding window. The trust had a credible Heat Decarbonisation Plan from a 2023 LCSF-funded study but needed integrated bid drafting and procurement support.
What we did
The project was structured as a bundled retrofit:
- 350 kWp rooftop PV across the outpatient block roof (2,100 m² unobstructed roof area)
- 220 kW thermal air-source heat pump system displacing the existing gas boiler in the outpatient and admin blocks
- Hydronic retrofit on the outpatient block (radiator oversizing, pipework upgrades) to enable heat pump operation at 50°C flow temperature
- BMS upgrade for occupancy-driven heating control
The carbon score on the integrated bid: 8.4 tCO2e/£100k of grant — well above the Phase 3b threshold of 6.5. Solar alone would have scored 4.6, below threshold.
The numbers
- Total project capex: £885,000 (£265k PV + £620k heat pump + retrofit)
- Salix PSDS Phase 3b grant: £885,000 (100% covered)
- Trust contribution: £0 capex (£28k internal project management costs paid from trust capex envelope)
- Annual electricity savings (PV displacement): £58,000
- Annual gas savings (heat pump): £92,000
- Annual electricity uplift (heat pump load): -£42,000
- Net annual savings: £108,000 (combined PV + heat pump)
- Annual carbon savings: 312 tCO2e
- Trust effective payback: 2.4 years on the £28k internal contribution
What happened
Commissioned August 2024 within the PSDS milestone schedule. M&V monitoring is now in month 9 of an 18-month obligation period; data is on track and being reported back to Salix as required. The trust has used the project as a teaching site for adjacent NHS trusts considering similar bids.
Why it worked
The trust started the HDP work early enough — 7 months of HDP development before bid submission. The bundled approach (PV + heat pump + retrofit + BMS) lifted the carbon score above the winning threshold. Solar alone would have failed scoring.
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