Question 1

Is a heat pump cheaper to run than a gas boiler?

Accepted Answer

It depends on the COP achieved and energy prices. At a COP of 3.0, a heat pump produces 3 kWh of heat per 1 kWh of electricity. With electricity at 26.11p/kWh and gas at 7.33p/kWh (Ofgem Q3 2026), the effective cost per kWh of heat is 8.7p (heat pump) vs 8.1p (90% efficient gas boiler). With an economy tariff or solar PV, heat pumps become clearly cheaper. Running costs are broadly similar for most homes.

Question 2

What is the BUS grant and how do I get it?

Accepted Answer

The Boiler Upgrade Scheme (BUS) provides £7,500 towards an air-source or ground-source heat pump, and £5,000 towards a biomass boiler (biomass is further restricted to rural, off-gas-grid properties). The grant is claimed by your MCS-certified installer and deducted from the quote. Eligibility: the property must have a valid EPC with no outstanding loft/cavity insulation recommendations (unless exempt), an MCS-certified installer, and you must be replacing a fossil-fuel heating system. Properties on mains gas ARE eligible for heat pumps — BUS has no off-gas-grid requirement for ASHP/GSHP (that is HUG2). The scheme runs until March 2028.

Question 3

Do I need bigger radiators with a heat pump?

Accepted Answer

Usually yes. Heat pumps run most efficiently at lower flow temperatures (35-45°C vs 60-75°C for gas boilers). At 45°C flow, radiators produce roughly 50-60% of their rated output, so you may need to upsize some radiators or add additional ones. Properties with underfloor heating are ideal for heat pumps as UFH works well at low temperatures.

Question 4

How much does a heat pump cost to install vs a gas boiler?

Accepted Answer

A gas combi boiler replacement costs £2,500-4,000 installed. An air source heat pump costs £8,000-14,000 installed before the BUS grant, or £500-6,500 after the £7,500 grant. Ground source heat pumps cost £15,000-25,000 before grants. The heat pump cost includes the outdoor unit, cylinder, controls and any radiator upgrades.

Question 5

What are the carbon savings from switching to a heat pump?

Accepted Answer

The UK electricity grid carbon intensity is around 136g CO2/kWh (DESNZ 2024 GHG conversion factors). At COP 3.0, a heat pump produces about 45g CO2 per kWh of heat. A gas boiler produces approximately 200g CO2/kWh of heat (natural gas 183g/kWh ÷ 92% efficiency per DESNZ 2024). Heat pumps cut heating carbon emissions by roughly 75%, and this improves as the grid decarbonises further.

Feature	Air Source Heat Pump	Gas Combi Boiler
Install cost	£8,000-14,000 (£500-6,500 after BUS)	£2,500-4,000
Efficiency	COP 2.5-4.0 (250-400%)	89-94% ErP
Annual running cost (3-bed)	£700-1,000	£700-1,000
CO2 per kWh heat	~45g (at COP 3.0)	~200g
Flow temperature	35-55°C (most efficient at 35-45°C)	60-80°C
Hot water	Needs cylinder (150-250L)	Instant (combi) or cylinder
Lifespan	20-25 years	12-15 years
Grant available	BUS £7,500	None

Heat Pump vs Gas Boiler — UK Costs

Side-by-Side Comparison

When to Choose a Heat Pump

When a Gas Boiler Is More Practical

Related Calculators

How We Calculate This

Frequently Asked Questions

Related Calculators

Gas vs Electric vs Oil Heating

Air Source vs Ground Source Heat Pump

Heat Pump Brands Comparison

Combi vs System vs Conventional Boiler

Was this calculator helpful?