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Low vs High Temperature Air Source Heat Pumps: Which is Best?

Becky Mckay
By: Becky Mckay
Updated: 9th March 2022

Low vs high temperature

When choosing an air source heat pump for your home, (if it is an air to water type), whether you have a low temperature or high temperature heat pump is a big consideration. If this is something you don't consider, you may end up with a heat pump incapable of heating your home or one that costs you more money on heating bills.

What is a low temperature heat pump?

Low temperature air source heat pumps are designed to heat the water in a property up to a maximum temperature of around 60 – 65°C. While this is fine for running hot water in a property, it can be a problem when it comes to your central heating. This is because most traditional central heating systems are only capable of heating a property effectively when the water temperature is between 75 – 80°C. Should you want to invest in a low temperature air source heat pump, you will also need to invest in compatible heating appliances for your home.

Low temperature heating appliances

There are 2 common types of low temperature heating appliance: underfloor heating and low temperature radiators. Both of these appliances use hot water to heat a property and only require a maximum water temperature of 55°C. Installing new underfloor heating is a lot more disruptive and expensive than replacing your existing radiators with low temperature ones. However, by installing underfloor heating in certain rooms, you can free up a bit of space around your home.

What is a high temperature heat pump?

High temperature air source heat pumps are designed to replace the heat provided by a gas boiler in your home without any need to alter the heating appliances around the property. They are capable of heating the water in your central heating system to temperatures of around 75 – 80°C. The same temperatures traditional gas boilers are capable of providing. While they may seem like the best option for the majority of homeowners with traditional central heating systems, there are some drawbacks to using a high temperature pump.

High temperature heat pumps require more power to run than low temperature heat pumps. This makes them less efficient to run and means that the energy bills of a property using a high temperature air source heat pump will be higher than those of a comparable property using a low temperature heat pump. High temperature pumps are often more costly to install too. However, as there is no extra cost for installing compatible heating appliances around the property, this could be negligible.

Which heat pump is best?

When deciding whether a low or high temperature air source heat pump is the best option for you, you will need to decide which suits your current circumstances best. If you've already invested in low temperature heating solutions such as underfloor heating, this will make your decision making process a lot easier. However, if you have a traditional central heating system, the best decision might not be as straightforward as you may think. Here are some things you will need to consider:

What heating appliances do I have?
What kinds of heating appliances are already installed around your property will be a big factor in whether a low or high temperature heat pump would be best for you. If you have a traditional heating system the most straightforward option would be to have a high temperature air source heat pump installed. An alternative option, which would save you more money on your energy bills, would be to replace your existing radiators with larger low temperature ones. However, you will need to consider where your existing radiators are placed and whether it would be easy to replace them. If there is enough space and you're happy to spend a little more in the short term, a low temperature heat pump could still be a good option.

How much space is there?
While air source heat pumps do not tend to take up much indoor space, the installation of larger low temperature radiators could leave your home feeling a little cramped. This issue can be resolved by using underfloor heating instead, but this is generally a much more costly option. Air source heat pumps don't only take up indoor space, they take up outdoor space too. As they require more power to produce more heat, high temperature air source heat pumps have larger outdoor units than their low temperature alternatives. This can mean they are not viable if you have a very small garden or no garden at all.

Is my home energy efficient?
If your home is not well insulated and is releasing a lot of its heat through single glazed windows or thin walls with no insulation, radiators with water at temperatures of 45°C and less will leave your home feeling rather chilly. While most low temperature air source heat pumps are capable of heating water to a maximum temperature of 65°C they are actually most efficient when providing water temperatures of around 35 – 45°C.

If there is no way to improve your home's energy efficiency and it is still losing heat, you will most likely benefit from investing in a high temperature air source heat pump. However, if your home has loft insulation, double glazing and a number of other energy efficient measures in place, a low temperature air source heat pump should be more than capable of keeping your home nice and warm.

Getting the best price

Once you have taken your circumstances into account and have decided which type of air source heat pump is best suited to your home, it is time to get installation quotes from professional engineers to see how much this will all cost.

To ensure you get the best possible price, we recommend getting several comparison quotes from heating engineers in your local area. This is something we can help with. By using the link below and answering some basic questions, you can get quotes from up to 3 heating engineers in your area and simply pick which quote is best for you.

Becky Mckay

About the author

Becky Mckay

Becky is one of our home heating and renewable energy experts and has a wealth of experience writing about the world of heating.

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