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

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 24p/kWh and gas at 6p/kWh, the effective cost per kWh of heat is 8p (heat pump) vs 6.7p (90% efficient gas boiler). With an economy tariff or solar PV, heat pumps become clearly cheaper. Running costs are broadly similar for most homes.

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

The Boiler Upgrade Scheme (BUS) provides £7,500 towards an air source heat pump or £7,500 towards a ground source heat pump. The grant is claimed by your MCS-certified installer and deducted from the quote. Your property must have an EPC (any rating), be an existing building, and not be on the gas grid or willing to disconnect. The scheme runs until 2028.

Do I need bigger radiators with a heat pump?

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.

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

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.

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

The UK electricity grid carbon intensity has dropped to around 150g CO2/kWh (2025 average). At COP 3.0, a heat pump produces about 50g CO2 per kWh of heat. A gas boiler produces approximately 215g CO2/kWh of heat. This means heat pumps cut heating carbon emissions by roughly 75%, and this improves as the grid decarbonises further.

Heat Pump vs Gas Boiler — UK Costs

Compare air source heat pumps with gas boilers for UK homes, covering running costs, BUS grant, carbon emissions and radiator sizing implications.

Side-by-Side Comparison

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	£600-900
CO2 per kWh heat	~50g (at COP 3.0)	~215g
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

When to Choose a Heat Pump

Well-insulated property (EPC C or better ideal)
Underfloor heating installed or planned
Eligible for the £7,500 BUS grant
Off-gas properties (replacing oil or LPG)
You want to future-proof against gas phase-out
Solar PV installed to offset electricity costs

When a Gas Boiler Is More Practical

Poorly insulated property not suitable for low-temperature heating
Very limited outdoor space for the heat pump unit
Tight budget and no BUS grant eligibility
High hot water demand where instant combi delivery is preferred

Related Calculators

Use the Heat Pump Sizing Calculator to size a heat pump, or the Boiler Size Calculator for gas boiler sizing.

How We Calculate This

Frequently Asked Questions

Last updated: April 2026

All calculations are estimates. Verify with your supplier.

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

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