Heat Pump Installation: What Happens From First Call to Switch-On

The heat pump installation process runs in order: a survey of your home, a heat loss design, a written quote, the grant application, the fitting, commissioning and a handover. In England and Wales your installer applies for the Boiler Upgrade Scheme grant and it is shown as a discount on your quotation and invoice. How long the job takes depends on your home and the survey.

An air source heat pump takes heat from the outside air and sends it to your radiators and hot water. Energy Saving Trust says air-to-water is the most common type in the UK, and that is the type this page follows.

Correct as of 6 November 2026. Grant amounts and rules on this page were checked against the GOV.UK grant notice (updated 20 October 2026) and Ofgem's guidance for property owners. Neither shows a change to the amounts.

Most surprises show up at the survey, because it decides what has to change before a heat pump can work well. Energy Saving Trust's installation guide, dated 20 October 2026, covers the same ground.

Radiators and pipework

Heat pumps send water to radiators at a lower temperature than a gas boiler, often 35 to 45 degrees Celsius. Your installer works out whether your radiators are big enough at that temperature.

Where they are not, the usual fix is a larger radiator, and single panel radiators can often become double panel without taking more wall space. Narrow microbore pipework can also struggle to move water quickly enough, so it may need replacing.

Hot water cylinder

A heat pump does not make hot water on demand like a combi boiler, so most homes need a hot water cylinder. An existing cylinder usually has to be swapped for one that suits a heat pump.

If you have no room for a cylinder, other options include a smaller heat battery or instant hot water heaters at the sink.

Outdoor unit position

The outdoor unit can be as large as 1 metre by 1.5 metres, roughly the floor space of two wheelie bins. It needs a firm, level spot, a platform where the ground is unsuitable, and a drain or soakaway for water.

Electrics and controls

The heat pump needs an electrical connection of its own. Many installers bring in an electrician for this and for the controls.

Insulation helps a heat pump work well, but you do not need a lot of it to have one fitted.

Questions about what the grant covers on a quote?

Sometimes the survey says the plan has to change before any fitting starts. It is better to hear that at the survey than halfway through the job.

• No space for a cylinder: the design moves to a heat battery or a different hot water setup, which changes the quote.
• Radiators that are too small: larger radiators go into the quote.
• Unsuitable ground or no drain nearby: the unit may need a platform, or a soakaway.
• A home that already has a low carbon system: the grant rules rule out swapping one low carbon system for another, so the funding route needs checking first.
• Another funding route: some households may qualify for the Warm Homes: Local Grant instead, which has its own eligibility rules.

FreeBoilerUpgrade.uk offers air source heat pump and Boiler Upgrade Scheme help alongside funded boilers and insulation. Our team can explain how the grant works and what the paperwork involves, so nothing in the process comes as a surprise.

Ready to talk through the grant side?