Indicative only. Bands derived from published Phase 3 and Phase 4 funded projects. A feasibility study with site survey, heat-loss model and Grant Carbon Cost calculation is the binding artefact for any Salix-portal application.
Worked example: 420-pupil secondary, gas heating
A 420-pupil primary at 3,200 m² GIFA burning 620,000 kWh/yr of gas, switching to ASHP. Annual gas-displaced kgCO2e is 620,000 × 0.18254 = 113,175 kg, with 25% remaining via electricity gives ~84,881 kg/yr. Over 20 years that is 1,697 tonnes lifetime. ASHP sizing at 1500 full-load hours = ~413 kW. Mid-band capital £1,700 × 413 = £702,100. £/tCO2e = £414. The scheme fails the £325 ceiling. Add a fabric-first package to drop heat demand 30%, and the ratio falls below £325. This worked example matches the calculator output to within rounding.
Calculation method
- Gas combustion factor 0.18254 kgCO2e/kWh (BEIS conversion factors).
- Heat-pump SCOP 3.0 (ASHP) or 3.8 (GSHP) for a school retrofit.
- Asset life 20 years (PSDS lifetime convention used in award lists).
- Capital cost bands per measure: midpoints based on published Phase 3/4 projects.
- Sizing heuristic: heat demand kW = annual kWh / 1,500 full-load hours.
This is indicative only. The Salix portal application requires a feasibility study with site survey, heat-loss model and a Grant Carbon Cost calculation evidenced by the measure supplier.
Related
£325 ceiling explainer, GCC threshold, case awards, ASHP measure page.