An air source heat pump (ASHP) is a renewable energy system that extracts ambient heat from outside air and amplifies it to provide space heating, cooling, or domestic hot water for buildings. It operates as a low-carbon alternative to traditional gas or oil boilers.
Explanation
ASHP systems use a refrigeration cycle involving a compressor, evaporator, and condenser. They absorb latent heat from ambient air (even at temperatures as low as -15°C) and transfer it indoors via refrigerant fluids. Key components include:
- Outdoor Unit: Contains a fan and heat exchanger to capture air.
- Indoor Unit: Distributes heat via radiators, underfloor heating, or air convectors.
- Heat Exchanger: Upgrades low-grade air heat to usable temperatures (typically 35–55°C).
ASHPs function efficiently in air-to-water (heats water for hydronic systems) or air-to-air (directly heats/cools air) configurations. Their performance is measured by the Seasonal Coefficient of Performance (SCOP), indicating units of heat produced per unit of electricity consumed. Modern ASHPs achieve SCOPs of 2.5–4.0 in UK climates.
Context in UK Retrofit & Building Sectors
In the UK, ASHPs are pivotal for decarbonising housing stock under the Future Homes Standard and net-zero targets. Retrofitting them into existing homes requires:
- Insulation Upgrades: To minimise heat loss and maximise efficiency (e.g., cavity wall or loft insulation).
- Emitter Compatibility: Larger radiators or underfloor heating are often needed due to lower flow temperatures compared to boilers.
- Electrical Infrastructure: Homes may require upgraded fuse boxes or dedicated circuits.
Challenges include higher upfront costs (£7,000–£13,000) and space for outdoor units, but grants like the Boiler Upgrade Scheme (up to £7,500) mitigate this.
Key Considerations for UK Homes
| Efficiency | Works best in well-insulated homes (EPC rating C or above) |
| Planning | Permitted development rights apply (England), but noise (<42dB) and placement rules exist |
| Maintenance | Annual servicing; lifespan of 15–20 years |
ASHPs are central to the UK’s electrification of heat strategy, reducing reliance on fossil fuels while aligning with 2050 net-zero goals