What Are the Disadvantages of an Air Source Heat Pump?

Higher Upfront Costs

The main disadvantage is the higher initial cost compared to a gas boiler. An air source heat pump costs £7,000-£13,000 installed, versus £2,000-£4,000 for a new gas boiler. However, the £7,500 BUS grant reduces this gap significantly, bringing the net cost to £2,000-£5,500.

When factoring in lower running costs (£300-£600/year savings vs gas), most homeowners recoup the additional investment within 7-12 years, after which the heat pump saves money every year for the remainder of its 20-25 year lifespan.

Outdoor Unit Noise

Air source heat pumps do produce some noise from the outdoor unit, typically 40-50 dB at 1 metre — similar to a quiet conversation or a modern dishwasher. Planning regulations require the unit to be at least 1 metre from any neighbouring boundary.

Modern heat pumps are significantly quieter than older models, and noise levels decrease rapidly with distance. At 5 metres, most units are barely audible. Premium brands like Samsung and Daikin have developed whisper-quiet models specifically for noise-sensitive installations.

Lower Flow Temperatures

Heat pumps work most efficiently at lower flow temperatures (35-45°C) compared to gas boilers (60-75°C). This means existing radiators may need to be upsized to deliver adequate heat, which adds to installation costs.

However, this disadvantage is easily addressed: underfloor heating works perfectly at low temperatures, fan-assisted radiators boost output without increasing size, and well-insulated homes may not need any radiator changes at all.

Space Requirements

You'll need space for the outdoor unit (roughly the size of a large suitcase) and typically a hot water cylinder inside your home (if you don't already have one). Combi boiler homes switching to a heat pump will need to find space for a cylinder.

The outdoor unit needs adequate clearance for airflow and should be positioned where it won't cause noise issues. Most homes can accommodate this without difficulty, but very compact terraced properties may need creative solutions.