Heat Pumps: The Complete Buying Guide
ASHP vs GSHP explained - costs, the £7,500 BUS grant, running costs compared to gas, and how to choose the right heat pump for your home.
Quick Summary
- ASHP cost: £8,000-£14,000 (before grant)
- BUS Grant: £7,500 off the cost of an air source heat pump
- Efficiency: 300-400% (COP 3-4) - 3-4 units of heat per unit of electricity
- Lifespan: 20-25 years with minimal maintenance
What Is a Heat Pump?
A heat pump extracts heat from the air, ground, or water outside your home and concentrates it to heat your radiators, underfloor heating, and hot water. Think of it as a fridge running in reverse - moving warmth from outside to inside.
Because heat pumps move heat rather than generating it by burning fuel, they're remarkably efficient. For every 1kWh of electricity consumed, a modern heat pump delivers 3-4kWh of heat - making them 300-400% efficient compared to a gas boiler's 90-95%.
Air Source vs Ground Source
Air Source (ASHP)
Extracts heat from outside air. Works down to -15°C. By far the most popular choice in the UK.
- ✓ Lower installation cost
- ✓ Easier to install (no digging)
- ✓ Suitable for most properties
- ✓ £7,500 BUS grant available
- △ Slightly lower efficiency in winter
£8,000-£14,000
Ground Source (GSHP)
Extracts heat from underground via buried pipes. Constant ground temperature means higher year-round efficiency.
- ✓ Higher efficiency (COP 4-5)
- ✓ More consistent performance
- ✓ Silent operation
- ✓ £7,500 BUS grant available
- △ Higher installation cost
- △ Requires garden space for trenches/boreholes
£20,000-£35,000
The Boiler Upgrade Scheme (BUS Grant)
The UK government's Boiler Upgrade Scheme offers grants of £7,500 towards the cost of an air source or ground source heat pump. The scheme runs until March 2028 and is available to homeowners in England and Wales.
BUS Grant Eligibility
Your installer applies for the grant on your behalf - the discount is taken off the invoice.
Running Costs: Heat Pump vs Gas Boiler
Running costs depend on electricity and gas prices, your home's insulation, and the heat pump's efficiency. With a COP of 3.5 and current energy prices, a well-installed ASHP typically costs similar to or slightly less than a gas boiler to run.
The gap widens significantly if you pair a heat pump with solar panels - generating your own electricity to power the heat pump can reduce heating costs by 40-60%.
| Heating System | Annual Cost* | CO₂/yr |
|---|---|---|
| Gas Boiler (90% eff.) | £1,050 | 2.7 tonnes |
| ASHP (COP 3.5) | £920 | 0.9 tonnes |
| ASHP + Solar PV | £450-£600 | 0.3 tonnes |
| Oil Boiler | £1,400 | 3.5 tonnes |
*Based on typical 3-bed detached house, 12,000 kWh heating demand, 2025 energy prices
Is My Home Suitable?
Most UK homes can accommodate an air source heat pump, but some factors make installation easier and more effective:
- Good insulation - cavity wall, loft, and double glazing make a big difference
- Space for the outdoor unit - roughly the size of a washing machine
- Larger radiators or underfloor heating - heat pumps work at lower temperatures than boilers
- Hot water cylinder space - heat pumps use a cylinder instead of a combi boiler
Get Heat Pump Quotes
Compare free quotes from MCS-certified heat pump installers in your area. BUS grant applied automatically.
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