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London & South-East England

Air Source Heat Pump Installation

Fabric first, then a heat pump sized for the house you actually have, not the one on paper.

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Accredited, certified installersOne point of contactFixed written quote

Is air source heat pump right for your home?

  • Homes that are already well insulated, or booking insulation with us at the same time
  • Houses with a boiler due for replacement and space outside for the unit
  • Homes with, or planning, solar panels and a battery
  • Owners who want to move off gas altogether
  • Whole house retrofits planned under PAS 2035

Air Source Heat Pumps: key facts

  • An air source heat pump moves heat from outdoor air into the home and delivers 3 to 4 kWh of heat for every 1 kWh of electricity (a SCOP of 3 to 4).
  • Indicative cost: £8,000 to £15,000 installed for a typical 3-bed including cylinder and radiator changes; larger homes £12,000 to £20,000.
  • Charged at 0% VAT until 31 March 2027 as an energy-saving material.
  • A heat pump runs best at flow temperatures of 35 to 50°C, so the walls, loft and floors must hold heat first.
  • Stay Warm’s free heat loss survey covers the insulation side; the installer’s MCS room by room heat loss calculation sizes the pump.
  • Installed by accredited, MCS certified installers, arranged and project-managed by Stay Warm.

What is air source heat pump?

An air source heat pump is an outdoor unit, roughly the size of a large air conditioning box, that draws heat out of the air even on a cold day and passes it into the water that feeds your radiators and hot water cylinder. Because it moves heat rather than making it, it delivers three to four units of heat for each unit of electricity it uses. It replaces the gas boiler, and it works best when it runs for long periods at a low, steady flow temperature instead of the short, hot bursts a boiler gives.

That low flow temperature is the reason insulation comes first. A gas boiler at 70°C can force heat into a leaky Victorian terrace or a 1930s semi with uninsulated solid walls. A heat pump at 45°C cannot, and the result is a house that never feels warm and a bill that is higher than the gas one was. Most London and South-East homes were built before any insulation standard existed, so the sensible order is loft, walls and floors, then the heating. A well insulated home needs a smaller pump, fewer radiator changes and less electricity.

Stay Warm surveys the house, fits the insulation with its own PAS 2030:2023 team, and then arranges the heat pump. An accredited, MCS certified installer carries out the room by room heat loss calculation, specifies the pump, cylinder and any radiator upsizing, and installs and commissions the system. You get one project manager and one written quote for the whole job.

Who does the work

Air source heat pumps are arranged and project-managed by Stay Warm. Stay Warm’s own PAS 2030:2023 team does the insulation first, then an accredited, MCS certified installer designs and installs the heat pump.

Air Source Heat Pumps cost guide

Indicative 2026 market ranges for London and the South-East. Your fixed quote follows a free survey and the installer’s heat loss design, and depends on pump size, the cylinder and how many radiators change.

Job typeIndicative cost
Heat pump, typical 3-bed, with cylinder and radiator changes£8,000 – £15,000
Heat pump, larger or detached home£12,000 – £20,000
Insulation first (loft, walls, floors)Quoted separately
Free heat loss surveyFree
MCS heat loss design, commissioning and paperworkIncluded

VAT: 0%. Air source heat pumps are energy-saving materials, so the installation, including the cylinder, pipework and radiator changes that form part of it, is charged at 0% VAT until 31 March 2027 (HMRC VAT Notice 708/6).

What a heat pump installation includes

Monobloc air source heat pump, sized from a room by room heat loss calculation
Unvented hot water cylinder, usually 200 to 250 litres, with a heat pump coil
Radiator upsizing where a room needs more output at a lower flow temperature
Outdoor unit on a wall bracket or ground base with a condensate drain
Controls set up for weather compensation, so the flow temperature follows the outdoor temperature
MCS certificate, DNO notification and manufacturer warranty

How a heat pump installation works

1

Free heat loss survey

We look at the walls, loft, floors, windows and ventilation, and tell you what insulation the house needs before a heat pump makes sense.

2

Insulation, then design

Stay Warm’s own team fits the insulation. The accredited installer then runs the MCS room by room heat loss calculation and specifies the pump, cylinder and radiators.

3

Fixed quote and installation

One written quote for the whole job. The accredited, MCS certified installer fits the system, normally in two to four days, with the boiler removed at the end.

4

Commissioning and handover

The system is balanced and the controls set up, and you receive the MCS certificate, DNO notification, warranties and a plain walk-through of how to run it.

Free survey & fixed quote

Book a free, no-obligation survey and we will send a clear, fixed written quote. One point of contact from survey to sign-off, and a written guarantee on the work.

Get a free quote

Air Source Heat Pumps FAQs

How much does an air source heat pump cost?
Indicative 2026 ranges are £8,000 to £15,000 installed for a typical 3-bed, including the hot water cylinder and radiator changes, and £12,000 to £20,000 for a larger or detached home. VAT is 0% until 31 March 2027. Insulation done first is quoted separately and is also 0%.
Do I really need to insulate first?
Yes, in almost every pre-1990s home. A heat pump runs at a lower flow temperature than a boiler, so the fabric has to hold the heat. Insulating first means a smaller pump, fewer radiator changes and a lower running cost. Our free heat loss survey tells you what the house needs and in what order.
Is a heat pump cheaper to run than gas?
Electricity costs roughly four times as much per unit as gas, so a heat pump needs to deliver more than about 3.5 units of heat per unit of electricity to beat a modern boiler on running cost. A well insulated home running at low flow temperatures reaches a SCOP of 3.5 to 4, and a heat pump tariff or solar improves it further. In a poorly insulated home it can cost more than gas, which is why the order matters.
Will I need new radiators?
Usually some. At a 45°C flow temperature a radiator gives out roughly half what it does at 70°C, so rooms with small radiators get larger ones or a second panel. Insulating the house first cuts the number that need changing. Underfloor heating works very well with a heat pump but is rarely worth adding just for it.
Is it noisy, and do I need planning permission?
A modern unit is around 40 to 45 dB at one metre, similar to a fridge, and quieter than most people expect. In England most installations are permitted development provided the unit meets the MCS 020 noise standard at the nearest neighbour’s window; listed buildings and some conservation areas need consent, and we check on the survey.
Who installs the heat pump?
An accredited, MCS certified installer designs, installs and commissions it. Stay Warm arranges the survey, does the insulation with its own team, manages the project and stays your single point of contact.
Is there a grant for an air source heat pump?
Yes. The Boiler Upgrade Scheme gives £7,500 off an air source heat pump in England and Wales when it replaces a fossil fuel or electric heating system, and £9,000 for homes heated by oil or LPG with no mains gas (21 July 2026 to 31 March 2027). The MCS certified installer who fits your heat pump applies for it and takes it off your quote, so you never handle the paperwork. The scheme is funded to 2030. On top of that the installation is 0% VAT until 31 March 2027. Details in our [heat pump grants guide](/guides/heat-pump-grants-2026).

Areas we cover

We arrange air source heat pump across Greater London, Surrey, Kent and Hertfordshire. See all areas we cover →

Related services

Free Heat Loss SurveyWhole House RetrofitSolar PanelsHome Battery StorageExternal Wall InsulationEV Charger InstallationDouble & Triple Glazing

Related guides

In-depth, independent guidance to help you decide.

Heat pump grants 2026Air source heat pump costInsulate before a heat pump?Where homes lose heatInsulation cost guideExternal wall insulation guideInternal wall insulation guide

Last reviewed September 2026 by Stay Warm Insulation.

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