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A Brief Guide to


1.    What is an Air Source Heat Pump?

A heat pump is used to provide heating and hot water for your home and would replace your typical gas boiler. Heat pumps take the heat from outside and use this to heat water for use in your home. Heat pumps can take the heat from the outside air, the ground or less commonly, the water.

Air Source Heat Pumps (ASHP)

A heat pump operates like an air conditioning unit, but in reverse. They use a heat source (the air, water or the ground) to heat a refrigerant, and then transfers that heat from the refrigerant to a hot water tank in your home.

Whereas a gas boiler will heat water to about 75oC, a heat pump delivers water at a much lower temperature of around 35oC – 45oC, which is still hot enough to heat your home, but also much more efficient. For this reason, heat pumps work best with underfloor heating, but radiators can still be used, although they need to be larger than those used for a gas heating system.

Other Types of Heat Pump

Due to more consistent temperatures below ground and in water, Ground Source Heat Pumps (GSHP) and Water Source Heat Pumps (WSHP) are even more efficient than ASHPs, but generally more expensive to install because of the work involved in installing the ground or water pipework.


2.    Benefits

Financial savings

Heat pumps are powered by electricity, so they are not free to run, but they’re far more efficient than other electric heating systems. An ASHP will convert every 1 unit of electricity it consumes into around 3 units of heat, making them 300% efficient. This makes them a much cheaper heating system to run than standard electric heaters or night storage heaters.

Having a heat pump also means that you may be eligible for income through the UK Government’s Renewable Heat Incentive (RHI) – see below for more information.

Carbon savings

Using a heat pump means that your carbon emissions will be about 70% lower than those with direct electric panel or storage heaters. Furthermore, if you have switched to a 100% renewable electricity tariff, the carbon emissions of your heat pump are effectively zero.

Gosport residents can check if they can save money by switching gas or electricity tariffs here.

Compared to those using a gas heating system, your emissions would be about 60% lower. Changing your system from gas to an ASHP will also improve local air quality.


3.    Property Suitability

Heat pumps work best with underfloor heating, so if you don’t already have underfloor heating you may need to consider the cost of installing it at the same time as your heat pump. Otherwise, heat pumps require oversized radiators compared to a typical gas boiler heating system. If you only have a small property, this may be more difficult.

Heat pumps also work best in properties that have good levels of insulation and little draught. If your home is old and not well insulated, you may want to consider insulating it, prior to installing the heat pump.

It is important that you get independent advice prior to having a heat pump installed. The Switched On Gosport team will be happy to help – just get in touch.


4.    Different ways to set up your system

The typical way to set up a heat pump system is to simply have a heat pump and hot water tank (thermal store). The water tank will also have an immersion heater, which is an electric heating element inside tank which can heat the water (like a big kettle) if the heat pump is not operating or needs a boost.

You will need to decide whether you will use underfloor heating, radiators or a combination of the two.

Solar panels can also be a good way to provide free electricity for your heat pump and immersion heater; particularly when coupled with a battery.


5.    Typical Costs

The cost of your system will vary depending on several factors: the size of heat pump needed, the type of system (air, ground, water), whether you need new emitters (underfloor heating and/or radiators) etc.

The Energy Savings Trust estimates a typical ASHP installation will cost in the region of £9,000 to £11,000. ASHPs may be part or fully funded under the Government’s Green Homes Grant scheme or the Council’s scheme in partnership with Warmer Homes. Contact the team today to see whether you might be eligible.


6.    Income from your system

Renewable Heat Incentive (RHI)

The Renewable Heat Incentive is a UK Government scheme which pays you for the heat you generate from a suitable technology for 7 years after it’s installed. The payments are based on the amount of heat demand that you have, but are capped so that thermally inefficient homes do not receive greater benefit. More on the RHI can be found here.


7.    Payback Period and Return on Investment

If you are replacing expensive heating systems like direct electric heaters, an ASHP could be a good choice. The savings from an ASHP should offset the capital cost over its lifetime. If you are replacing gas central heating, which is relatively cheap to run, the apparent payback may be less.

To ensure you get the maximum payback, try and make use of any government incentives, such as the Green Homes Grant – Local Authority Delivery Scheme and the RHI.


8.    Installation

Heat Pumps are relatively easy to install, especially if you’re building a new property or refurbishing an existing one. Space is required for the hot water tank (thermal store) and the heat pump, plus the external air handling unit.

Things you may want to look for:

  • Accreditation: any funding scheme (current or future) will typically require you to use an accredited installer to access the funding so it is work considering this.
  • Who will be doing the work? Many installers create sub-contract jobs and you should ask if they will do this and if so, to who?
  • Reviews or case studies: If they are reputable (third party reviews or case studies)


9.    Accreditation

MCS certification:

This covers low-carbon heating installer and confirms the install is completed by a certified installer who has passed the quality and technical standards. You can read more on MCS here.


10.    Maintenance

Heat pumps are relatively low maintenance but will require annual servicing, as would a gas boiler. You can expect an ASHP to last for around 15 to 20 years, which is longer than a gas boiler.


11.    Useful links