240 kW PV + Air-Source Heat Pump PSDS Phase 4 Bundle on a Yorkshire FE College
- System size
- 240 kW PV + 180 kW air-source heat pump bundle
- Annual saving
- £71,000 combined (PV + heat pump operational savings vs gas)
- Payback
- Zero capex
- Location
- Yorkshire
Scenario
A Yorkshire general FE corporation operating a single large 11,000 sqm urban campus faced two coincident estates pressures in 2025: (1) the main building’s 1980s gas boilers were at end-of-life with a £180,000 replacement cost looming, and (2) the corporation board had committed to a 50% scope-2 reduction by 2030 under their AoC Climate Action Plan. The Sustainability Lead (a recent appointment from a sustainability consultancy background) saw the opportunity to bundle PV with heat decarbonisation in a single PSDS Phase 4 capital grant application — a route that would deliver both interventions at zero net capital exposure to the corporation.
What we delivered
PSDS Phase 4 bundled bid: 240 kW PV + 180 kW air-source heat pump
- 240 kW PV array: Distributed across two roof slopes — 160 kW on the main teaching block south-east aspect, 80 kW on the sports hall south aspect. Battery storage 150 kWh in main plant room. Designed for high self-consumption (year-round adult cohort + sports hall lighting baseload).
- 180 kW air-source heat pump: Replaced the end-of-life gas boilers. 4-pipe heat pump system with low-temperature radiator upgrade across the main teaching block. Hot water demand fully transitioned to electric.
The two systems were designed as one integrated solution: heat pump electricity demand becomes baseload for the PV self-consumption, lifting PV self-consumption rate from ~55% (PV-only design) to ~74% (bundle design). The combined carbon saving against the pre-install baseline (gas + grid) was 312 tCO2e per year — substantially higher than either intervention alone would deliver.
Funding
100% PSDS Phase 4 capital grant — zero capital exposure for the corporation:
- Total project capex: £620,000 (PV: £215,000 + heat pump: £405,000)
- PSDS Phase 4 capital grant: £620,000 (100% grant)
- Net cost to corporation: £0
- Annual energy savings (operational): £71,000 (PV self-consumption + avoided peak-tariff gas + reduced gas standing charges)
- Net cash-flow benefit year one: £71,000
The PSDS bid scored in the top 4% of Phase 4 applications in the round, driven by the combined carbon score. A PV-only bid would have ranked outside the top 30% of the same round. The Sustainability Lead later reported: “The bundle was the entire bid strategy. We modelled PV-only as a comparison, and it wouldn’t have funded under PSDS — the scoring threshold was too high for standalone PV in that round.”
PSDS Phase 4 bid mechanics
The bid was scored on tonnes of CO2 equivalent saved per pound of grant. Key features of the winning bid:
- Integrated design — PV and heat pump engineered to share the same building services backbone, reducing total infrastructure cost
- Auditable baseline — 36 months of pre-install gas and electricity meter data formed the carbon baseline calculation
- Skills England linkage — bid narrative explicitly tied to T-Level Building Services Engineering curriculum delivery and apprenticeship green-skills routes
- AoC Climate Action Plan evidence — the install would account for 67% of the corporation’s 2030 scope-2 reduction target on its own
- Realistic 25-year operational projection — including modelled electricity price inflation, heat pump CoP degradation over time, and PV panel degradation
The bid was written by us in collaboration with the Sustainability Lead and the Director of Finance. Application-to-award turnaround: 17 weeks (faster than the typical 22 weeks for Phase 4 — credited by the Salix processor to the quality of the supporting evidence).
Programme
Phased across two academic terms:
- Autumn 2025: Heat pump install (replaced end-of-life gas boilers, no service interruption — old boilers ran until the heat pump was commissioned)
- Spring 2026: Low-temperature radiator upgrade across teaching block (mostly evening and weekend work to avoid classroom disruption)
- Summer 2026: PV install + battery commissioning + integration with heat pump for self-consumption optimisation
- Autumn 2026: First full term of integrated operation; live-generation dashboard data live in reception and across the apprentice common room
Compliance
- Permitted development on the PV (Class A Part 14 GPDO 2015)
- Heat pump planning permission (under MCS-certified design — permitted in most cases but the local authority requested confirmation of the noise assessment)
- MCS commercial certification on both the PV install and the heat pump install
- KCSIE 2025 safeguarding — full induction for both install programmes
- G99 DNO application for the PV; G99 also for the heat pump (which exceeded 17 kW per phase on the electrical draw)
- Asbestos R&D survey on the 1980s building — clear status on the roof areas selected; some ACMs in the boiler room cupboards (managed under Type 3 enclosed protocols during the heat pump install)
- ESFA Post-16 Audit Code — PSDS bid auditable; corporation board minute formally recorded
Outcomes
- Year one actual PV generation: 228,000 kWh versus modelled 220,000 kWh (+3.6%)
- Year one heat pump CoP: 3.4 seasonal (above modelled 3.2)
- Year one actual combined energy savings: £76,800 versus modelled £71,000 (+8.2%)
- Year one carbon saving: 318 tCO2e versus modelled 312 (+1.9%)
- Featured in the Salix Phase 4 case study round-up 2026 publication
- AoC quarterly bulletin feature — exemplar PSDS bid case study
- T-Level Building Services Engineering cohort ran the install as a 12-month synoptic project — three cohort members went on to apprenticeships with renewable energy installers
- Sustainability Lead presented the bid mechanics at the EAUC FE Climate Roadmap regional conference
What the Sustainability Lead said
“PSDS Phase 4 is highly competitive — the carbon score threshold is hard to hit with a pure-PV bid. But once you bundle PV with heat pump, the combined score lifts you into a different ranking band. The bundle also makes design sense — heat pump baseload is exactly the year-round daytime electricity demand that lifts PV self-consumption from mediocre to excellent. We got a £620,000 capital intervention with zero net cost to the corporation, and we hit 67% of our 2030 scope-2 target in a single project. That’s the case for the bundled bid in one sentence.”