What are pros and cons and cost of installing an Airsource Heat Pump vs Gas boiler?

What are pros and cons and cost of installing an Airsource Heat Pump vs Gas boiler?

Cost Comparison of Gas Boiler vs Air Source Heat Pump

1. New Gas Boiler Installation:
Typically costs between £2,100 and £3,000 including VAT.

2. Air Source Heat Pump Installation:
Costs range from £13,000 to £16,000 depending on the size of the home and how many radiators need to be installed.

3. The UK government currently offers a £7,500 subsidy under the Boiler Upgrade Scheme (BUS), which brings the effective cost down to around £5,500–£8,500 for most homes.

Installation of Air Source Heat Pumps

Air source heat pumps are ideal for refurbishment projects, particularly when floors are being lifted. Why? Because this gives the perfect opportunity to upgrade your pipework to 22mm, which is essential for improving flow rate and getting the best performance from your system.

Heat Pump Efficiency: Flow Temperature Matters

Heat pumps work most efficiently at lower flow temperatures—between 45°C and 55°C. This is significantly lower than a traditional gas boiler, which typically operates at 70°C. While most heat pumps can reach higher flow temperatures, doing so increases energy consumption and running costs significantly.

Yes, you can still turn the thermostat up and down, but if you’re expecting boiler-like performance at 70°C, be prepared for higher electricity bills. Keeping it in the 45–55°C sweet spot is key to long-term savings.

Bigger Radiators & Upgraded Pipework

To heat your home effectively at these lower temperatures, you’ll usually need:

• Bigger radiators with larger surface areas
• Upgraded pipework, ideally resized to 22mm to maximise flow
  This is why heat pumps are a better fit for full refurbishments, where floors are already being lifted and pipework can be replaced without added disruption.

Open Loop vs Thermostatic Valves

For maximum efficiency, radiators should ideally be installed on an open loop system:

• No thermostatic radiator valves (TRVs)
• Only lockshield valves are used
• All rads heat together based on the central thermostat
  This does mean you’ll lose individual radiator control, but it improves efficiency and flow. Open loop system is not essential and you can retain your TRVs and existing pipework but slightly compromises performance. If you’re serious about squeezing out every last bit of efficiency, go open loop—but be aware it means re-running pipework from scratch.

Retrofitting Without a Refurb

If you’re not doing a full refurb and floors are staying put, existing 15mm pipework can still work—but it does restrict flow rate. You’ll likely need to upsize your radiators to compensate for the lower flow temperature to get similar heat output to a traditional gas system which operates at an average of 70 and up to 80 degrees.

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