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Air Source Heat Pumps

  1. What are Air Source Heat Pumps?
  2. How do they work?
  3. What are the benefits?
  4. Grants
  5. Frequently Asked Questions about Air Source Heat Pumps



Sol2o offer consultation, design, installation and maintainance of Air Source Heat Pumps.


For an Air Source Heat Pump evaluation or a complete energy performance assessment of your property call us now on 0800 2800 020 Or click here to register with us.


What are Air Source Heat Pumps?


Heat pumps are an effective and environmentally friendly solution for heating and cooling all types of buildings, households and commercial premises. They harvest energy from one source, enhance it and transfer to another in a very efficient manner using relatively small amounts of energy. Air source heat pumps are used for heating purposes with the vehicle that they harvest the energy from being, free and plentiful, the air.

The atmospheric air is heated by the sun on a daily basis, creating a source of free low-grade heat. The heat pump can extract this heat from the air and concentrate it from a low-grade heat to temperatures that are high enough to be used for heating water, homes and commercial premises. They operate at optimum performance all year round, no matter what the outside temperature is. Air source heat pumps have the ability to extract useful heat from the outside air at temperatures as low as -15°C and can generate hot water up to 65°C.


How do they work?


Air source heat pumps use relatively small amounts of electricity to circulate and compress fluid with an electric pump. It then extracts and upgrade the temperature of the free energy drawn from the outside air sufficiently for space and hot water heating. In the same way that a fridge uses refrigerant to extract heat from the inside to keep the food cool, air source heat pump extracts heat from the outside air, and uses it to heat the property and or provide hot water.

Every air source heat pump has four main parts:

The evaporator:

This collects heat from the outside air, pre heated by the sun, which is then drawn into the unit by the fan and expelled through the evaporator fins. The evaporator has liquid refrigerant passing through it, which is at a considerably lower temperature than the outside air, therefore the air gives up the heat to the refrigerant, which then vaporises.

The compressor:

This preheated vapour now travels to the compressor where it is compressed and upgraded to a much higher temperature.

The condenser:

The hot vapour now enters the condenser where it is surrounded by water from the heating system. The heat is given up to the cooler water and the now cooler refrigerant returns to its former liquid state but still under high pressure from the compressor.

The expansion device:

This high pressure is then released by passing the liquid through the expansion device and from there it returns to the evaporator and the cycle starts again.

Air source heat pumps can be incorporated into monivalent or bivalent heating systems in both new buildings and existing properties.

Monivalent Heating Systems

This solution is ideal for new build, very well insulated properties or existing properties with low temperature space heating requirements. The heat pump is used on its own and sizes to provide 100% of the heating requirement even on the coldest day of the year as well as the direct hot water requirement. The initial investment cost may be higher but the energy consumption is the lowest of all systems.

Bivalent and integrated systems

This solution is ideal for retro fitting into existing properties when the heat pump is combined with a secondary heat source or an existing fossil fuel boiler, allowing the user to retain their existing boiler for additional heating capacity. The heat pump would provide the largest proportion of the annual heating requirement with the existing boiler topping up on the coldest days.


In order to determine which option is most suitable for a property or project depends on a number of factors, which Sol2o will take into account prior to designing a solution. They include insulating the building to its required level. Money spent on upgrading insulation levels can save a considerable amount on the system costs.
Air source heat pumps work best with heating systems that are optimised to run at lower temperatures than is commonly used in UK boiler and radiator systems. As such they make an ideal partner for underfloor heating systems.

What are the benefits?


Reduce Energy bills by 40%

With a properly sized and installed air source heat pump you may be typically cut your bills by up to 40% if you are using a traditional boiler. They are extremely cost effective where mains gas is not available.

Improved Efficiency

Traditional boilers create heat through the burning of fossil fuels, modern heat pumps are extremely efficient. Extracting heat from the renewable source requires just 1KW of electrical input in order to generate 3KW to 5KW of heating output. Therefore they are 3-5 times more efficient than fossil fuel boilers.

Reduce your impact on the environment

Fossil fuels have a particular detrimental effect on the environment, as when these fuels are burned, carbon dioxide is released into the atmosphere contributing to global warming. Heat pumps can reduce carbon emissions compared to gas central heating systems by approximately 50%.

Lower maintenance costs

The technology inside a heat pump works on similar principles to those of a domestic fridge, but in reverse. Hence there is no need for regular servicing or annual safety checks and maintenance is minimum.

Ease of installation and use

The compact outdoor unit can be located where convenient and requires no drilling or excavation work to collect heat. The system can be connected to low temperature radiators and underfloor heating systems and can be configured for use in both new and refurbished applications.



Sol2o can offer advice on appropriate grants available to you and help you in the application process. For more information regarding grants for renewable technologies please click here.


Frequently Asked Questions about Air Source Heat Pumps



Do they make much noise?

No is the simplest answer, they have been designed to keep noise and vibration to a very low level.

How efficient are they?

Heat Pump Systems can be over six times as energy efficient as the most efficient gas or oil boiler. Instead of burning a fuel and producing the associated emissions they simply move energy that already exists, stored solar energy.

Can under floor heating be used with a heat pump?

Yes under floor heating, radiators or a mix of both for heat distribution in your building. In commercial buildings, air distributed systems can be used.

Will it heat a building on the coldest winter day?

Yes it will. Thousands of these systems have been installed for many years in some of the most northern parts of Scandinavia where the winters are very hard and long. The key is the design and specification process so the system provides enough energy for the application.


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Air Source Heat Pump

Air Source Heat Pump

Air Source Heat Pump