Air source heat pumps

Heat pumps are not a new technology, and millions are already heating homes very effectively across Europe. They are particularly common in the colder Nordic countries and in France and Italy.

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What is a heat pump?

An air source heat pump is an external unit that converts air from outside the house into heat. It acts almost like a refrigerator in reverse. The heat from the air is extracted and circulated into your house providing an efficient alternative to more traditional heating systems.

The only electricity used is to run the compressor and circulating pump. This allows it to transfer more heat into your home than it takes to run, making it more efficient than a gas boiler. It could lower your fuel bills too

Watch this video here to find out more.


This diagram and 3 steps explain how a heat pump create heating and hot water.

  1. The air source heat pump absorbs heat from the air outside, into a liquid called a refrigerant. This heat can be extracted from temperatures as low as -15°C Using electricity, the refrigerant is then compressed, which increases its temperature.

  2. This can now be used to provide heating and hot water to your home.

  3. You can now use your stored hot water for showers, baths and taps all year round.

Top Tip – It’s advised that you control the heat by the thermostat only and leave radiator values on the highest setting. 

Remember – If you’ve not had a demo and do not understand how to use your heat pump, please  contact us

A heat pump is very different to a gas or oil fuelled boiler.  Many people think it’s more expensive to run a heat pump and don’t often use it in the correct way, meaning it appears the heat pump isn’t working effectively.

When installed, the heating system is designed to ensure you get maximum efficiency ensuring radiators are the right size and your home is well insulated.

Using a heat pump exactly like a system such as a gas combi boiler, where you set the system to run for an hour here and there, or press boost for it to come on instantly, will not work and your home will not get warm.

It’s important you keep the heat pump running constantly to warm the fabric of the property, and then keep the heat pump running to maintain that core temperature. Then via the control panel, set the temperature to raise during the day, and fall in the night.

Once the fabric of the property has reached the right temperature, it will take less time and electric to raise the temperature when you need it to be warmer.  This is the most efficient and cheapest way to use a heat pump.

The temperature range should be set to suit your comfort and be between 16°C – 21°C, ideally at 18°C.

How a heat pump affects your electric bill depends on several factors, including:

  • What fuel your previous heating system used and how much that cost
  • Your electricity tariff
  • The type of heat pump installed and how efficient it is
  • How you use the heating system
  • The design of your central heating system
  • Your location and its average air temperatures throughout the year

Due to the current high cost of electricity, compared to a gas or oil fuelled boiler, you may see your bills rise.  However, this should be offset from the money you would’ve paid for gas or oil.

  1. Take the time to fully understand your heating controls and how best to set up the heat pump in line with your daily routine.
  2. If you’ve not had a demo and do not understand how to use your heat pump, please contact us.
  3. Remember that the harder a heat pump works, the more electricity it will use. For the most cost-effective results, set your pump to provide heat at a lower temperature over a longer period.
  4. Make sure there are no items obstructing the external unit so that a steady flow of air is maintained. Some of the main things that can block the heat pumps vents are:
  • snow or ice
  • leaves
  • moss
  • pet hair
  • plant pots
  • garden sheds
  • children’s toys
  • bins

By keeping the heat pump and the area round it clear, the pump will be more efficient and use less electricity. You can clean the heat pump by using soapy water and a sponge.

  1. Move onto the most economic electricity tariff.
  2. Ensure that the pressure gauge on the unit is within the correct range. Most units should be set up between one and two bar of pressure. 90% of the faults reports to Ongo relate to the pressure being wrong. By contacting us, we can help you reset the pressure gauge.
  3. If you see warnings on the control screen, don’t ignore them. Keep an eye on the fault log and see if you have recurring fault messages, report it to us.
  4. Don’t worry if you see water dripping from the back of the heat pump, they are designed to do that. – This occurs during the defrost cycle.
  5. If there is a fault with your heat pump, a member of our specialist team at Hales & Coultas will visit you. Within most cases, we will need to visit to inspect and then come back with the necessary part.
  6. Your home is well insulated to trap in heat, please do not disturb or move the insulation that is in your loft.
  7. Always close windows and doors when the system is in use. Letting heat escape into other rooms will reduce the warmth you feel from the system.

Will a heat pump keep my house warm?

Heat pumps will produce heating and hot water even when it’s ice cold outside and as a sustainable technology they’ve been designed to run at more efficient temperatures than a boiler.

Can a heat pump heat my home when its cold outside?

Heat pumps provide heat from the outside air like how air conditioning can provide heat in your car when it’s cold. They’ll pull heat from the air in temperatures as low as -27°C. There are more heat pumps in colder European countries than anywhere else in the world. The UK climate is actually quite warm.

Heat pumps work much harder when it’s cold, but the same is true of all heating systems. They are normally placed a few inches above the ground and above all but the heaviest falls of snow. Its important you remove any snow from around your heat pump to ensure it runs efficiently.

How loud is a heat pump?

Noise from a heat pump is created by large fans moving air across the heat exchanger.

Unless the heat pump is working very hard (ie in cold weather or producing high temperature water), you can expect the noise to be a similar volume to a fridge, if you were standing within a couple of metres. You could easily hold a normal conversation next to it, without raising your voice. As it gets colder outside, this noise will increase while it’s operating, but should still allow you to hold a conversation easily, only raising your voice a little.

Are heat pumps safe?

Heat pumps are remarkably safer than combustion-based conventional boilers such as gas or oil.  They emit no toxic waste and do not heat water to near-boiling temperatures. Regular maintenance reduces theoretical risks of leakage, electrical failure, and mould build-up.

With regular scheduled maintenance, a heat pump will operate for 15 years or more.

We will visit you every year to do an annual check and ensure your heat pump is in good working order.  This visit is important because if your heat pump isn’t running efficiently, it could be costing you money.

During the visit, you can ask our engineer any questions and they will check that you know how to use the system and ensure the thermostat is set correctly.

Please ensure the area round the heat pump is clear when we come to service it. 

Heat pumps are one of the forms of low carbon heating that are critical to the UK’s transition to net zero. They use electricity – so can be powered by renewable energy such as solar or wind – and are over three times more efficient than gas boilers.

For every unit of electricity they consume, a well-installed and reasonably high-spec model will produce 3 units of heat. This would give it an efficiency of 300%, which is much higher than a new condensing gas boiler which may achieve an efficiency of 90% – 98%.

In other words, heat pumps are over three times more efficient than gas boilers. And because a unit of electricity currently emits the same as a unit of gas, heat pumps deliver significant carbon savings.

For more information on Ongo’s environmental and NetZero journey click here.