Would an air source heat pump be suitable for my home?

An air source heat pump is suited to a well insulated and draught-proofed home. You will need space to install it on an outside back or side wall with plenty of space around it to get a good flow of air. You will achieve a faster payback if you are replacing your oil or LPG gas based heat source with a heat pump. It may not be so cost-effective if you are using mains gas.

How does an Air Source Heat Pump work?

An Air Source Heat Pump essentially works like a fridge in reverse! A heat pump is mounted on the back or side outside wall of your house. It is about the size of an air conditioning unit and connects through the wall into the heating and hot water circuits of your house (a heat pump is used instead of a boiler).

It works by extracting the heat from the surrounding air, absorbing it at low temperature into a fluid. This fluid then passes through a compressor and heat exchanger to increase the temperature and extract heat which is then delivered to the heating circuits of the house in for example the form of hot water for radiators. This is known as an air-to-water system distributing heat via your wet central heating system.

Heat pumps work much more efficiently at a lower temperature than a standard boiler system would. So they are more suitable for underfloor heating systems or larger radiators, which give out heat at lower temperatures over longer periods of time.

There are many different pumps available how do I know which to choose?

There are over thirty different makes of heat pumps available on the market in the UK which can make it difficult to choose. We advise that price should not be the only factor taken into consideration otherwise you could end up not making the savings that you thought you would and you could quite literally be left out in the cold!

We only install Mitsubishi Ecodan pumps as these are the one of only two makes currently available with an inverter driven compressor. This means that they have a much lower electricity demand and are therefore much more efficient.

Savings and system costs

The average cost of a fully installed system is between £4,000 - £8,000 depending on system size and set-up. Savings of up to 60% on your oil or LPG gas bill can be achieved. There are running costs to take into consideration as the pump runs on electricity but because air source heat pumps are so efficient (the Mitsubishi Ecodan pumps that we use is typically 300 -400% efficient) it generally costs less than modern gas boilers to run !

Adding solar energy will save even more!

Air Source Heat Pumps are particularly well suited to solar pv or solar thermal systems – if you already have a system then this will work exceptionally well. We are fully accredited to fit all technologies and offer a very attractive discount if you wish to install an air source heat pump system combined with solar pv and/ or solar thermal.

Are they noisy?

Noise used to be a real concern for heat pump users. Nowadays noise reduction has dramatically improved. It should be noted however that they are not silent in operation and some pumps can be noisier than others. Care therefore needs to be taken on where the pump should be sited e.g. not under a window or where a neighbour would be affected by it.

The heat pump make that we use Mitsubishi Ecodan is one of the better ones on the market at typically 48dBA.

Will it be able to satisfy all my heating a hot water requirements?

A correctly sized and well installed system should be able to satisfy 100% or your heating and hot water requirements all year round. The system we use will heat your tank water used for showers etc. to 55 degrees.

Air source heat pumps work most effectively with low level heat distribution systems such as underfloor heating or larger radiators. When it is used to heat tank water for showers which require a higher temperature its efficiency will drop to around 200–250%. This makes the addition of a solar thermal system to generate hot water during the summer months very effective.

I have an oil fired central heating system using radiators how will this affect an air source heat pump?

Air source heat pumps work most effectively with low level heat distribution systems. This means that depending on the size of your radiators you may need to replace them with larger radiators. With a traditional radiator based central heating system people used to blast the system up to high temperatures a couple of times a day – sometimes so high that the radiator is too hot to touch. The system would then turn off and on to maintain the required room temperature. This is not very energy efficient and not suited to heat pumps.

Heat pumps work best distributing heat at a lower temperature over a long period of time. The optimum is around 35-40 degrees compared to the 70 degrees that radiators are traditionally heated to. So as not to change your comfort level larger radiators are needed and they need to running for longer time periods. The rule of thumb is 1.3 times larger but if you can double the size then you will get better efficiency and therefore greater cost savings from your system.

Will it provide hot water for showers?

In a nutshell yes. The Ecodan heat pump range that we install will heat your tank up to 55 degrees which is plenty hot enough for showers and baths. When the heat pump is used to heat tank water its efficiency will drop to around 200 – 250%. This makes the addition of a solar thermal system to generate hot water during the summer months very effective.

How is an air source pump different from a ground source heat pump?

Both ground source and air source heat pumps do the same job of providing heat for your home and provision of hot water.

A ground source heat pump extracts heat from water in the ground instead of using the air. This heat is then compressed and distributed as space or hot water heating. Ground-source heat pumps tend to have higher efficiency levels than air source heat pumps in winter months as they are not reliant on the variable air temperature as their heat source. Ground source heat pumps are installed using underground arrays of pipes or boreholes. Both of which require a significant amount space and causes a higher level of disruption than installing an air source heat pump.

Installation costs and time tend to be higher for ground source heat pumps.

Do I need planning permission?

From 1st December 2011, domestic air source heat pump systems in England will be classed as Permitted Development provided that they comply with certain criteria, including:

• there is no wind turbine at the property
• the external unit is less than 0.6 m3 in size
• the unit is more than one metre from the edge of the householder's property
• it is not on a pitched roof, or near the edge of a flat roof
• it meets additional criteria if in a conservation area, World Heritage Site etc.

This list is not comprehensive and full details can be obtained via The Energy Saving Trust at www.energysavingtrust.org.uk or by contacting your local planning office.

For installations in Wales and Nothern Ireland planning permission is required. Installations in Scotland may also be considered permitted development but they have different criteria details can be found at www.energysavingtrust.org.uk or by contacting your local planning office.