Is a High-Temperature Heat Pump Right For You?

In recent years heat pumps have been recognised as having an important part to play in decarbonising our homes. It is expected that 80% of homes will move to a heat pump in the future although the exact timings for this are not yet known. The remaining 20% of homes will most likely be connected to heat networks using a large heat pump or other sources of clean energy. These networks will be communal systems that heat entire blocks of flats, villages, and even towns. 

A heat pump is an excellent way of using electricity to heat your home in an energy-efficient way. As heat pumps don’t produce heat by burning fossil fuels, they are a better choice for the environment than gas and oil boilers. A heat pump uses technology very much like that found in a refrigerator or an air conditioner. It extracts heat from a source such as the surrounding air (air source heat pump), geothermal energy (ground source heat pump) stored in the ground, or nearby sources of water (water source heat pump) or waste heat from a factory. The heat pump then amplifies and transfers the heat to where it is needed. Unlike an electric panel heater, for example, a heat pump has a compressor, which increases the amount of heat that can be generated from each unit of electricity. For a panel heater, that ratio is 1:1 but for most heat pumps such as the air source heat pump on the UK market today the ratio is likely to be 1:3 to 1:4 making it a very efficient substitute although many factors can affect this. Heat pumps are also easy to maintain and operate. 

There are, however, some disadvantages and factors to consider when installing a heat pump. As heat pumps require electricity to work you will probably see a small increase in your electricity usage unless you are replacing fuel types such as LPG when you will definitely save money.  Currently, electricity is still more expensive per unit than gas. It’s worth contacting your energy supplier to see whether they have a heat pump electricity tariff which may be cheaper and more suitable for an electric-based heating system. 

Unlike boilers which are high-temperature systems most heat pumps operate at a lower flow temperature which means that to ensure heat can be effectively transferred into the space within your home, sufficient heat emitter surface area is needed, and this is why correctly sizing the heat emitters is so important. It is not always possible to use your existing radiators with a low-temperature heat pump. It will very likely be necessary to replace them with larger radiators or an underfloor heating system. 

The design and installation of a heat pump system needs more planning and preparation than traditional boiler systems. A detailed heat loss calculation should be carried out on your property to ensure it is well-insulated which is key for an effective low-temperature heat pump system. There also needs to be an assessment of the heat pump output required as well as the correct sizing of the selected heat emitters.

Though low-temperature heat pumps can comfortably heat most homes, high-temperature heat pumps can match gas and oil boiler temperatures without having to make any changes to your home. 

To generate three or four units of heat for every unit of electricity consumed the temperature of the fluid running through a low-temperature heat pump needs to be lower than that delivered by a conventional boiler. Though most air-source heat pumps and ground-source heat pumps operate at a maximum flow temperature of 55degC to be efficient they are better suited to running at flow temperatures of around 35°C to 45°C. Gas, oil, and biomass boilers on the other hand produce water temperatures of 60degC centigrade to 80degC. The UK government has recently been campaigning to get all households to reduce the flow temperature on their boiler to 60degC to save energy and reduce bills. The higher temperature is the most significant difference between the different heating technologies and is the biggest barrier to overcome when trying to retrofit homes with a low-temperature heat pump system and replace a traditional boiler. The installation of low-temperature heat pumps may well necessitate the installation of new compatible radiators and new plumbing.

However, this is where high-temperature heat pumps come into play. They can heat your home to the same level of warmth and at the same speed as a gas boiler. A high-temperature heat pump can reach between 60degC and 80degC which enables you to heat your home quicker than regular heat pumps without needing to buy new radiators or insulation. High-temperature heat pumps use more superior refrigerants than low-temperature heat pumps to be able to achieve this. 

Most high-temperature heat pumps use R290 or R32 which are better for your home and the climate. They also come with industry-leading weather compensation controls. According to a recent government report, on average, high-temperature heat pumps have to raise their flow temperature above 65degC less than 1% of the time due to these technological advances.

High-temperature heat pumps can provide domestic hot water at the same temperature as boilers at around 60degC to 80degC whereas regular low-temperature heat pumps supply water at 45degC to 55degC. 

With improvements being made to the technology of regular heat pumps on an ongoing basis, an increasing number of models are reaching 60°C to 65°C. High-temperature heat pumps rarely have to reach these higher temperatures. 

Due to this fact and their usually superior refrigerants, high-temperature heat pumps are now usually just as efficient as low-temperature heat pumps. They have been shown to be almost three times as efficient as a central heating boiler. 

The Committee for Climate Change has identified high-temperature heat pumps as a viable option for many homes where low-temperature heat pumps are not practical. High-temperature heat pumps can use existing radiators with little or no adjustment. 

Most UK homes are set up to run with a gas or oil boiler and high-temperature radiators. If an old-style non-condensing boiler is being used, temperatures from the boiler to the radiators are 70-80 degrees Celsius. For modern condensing boilers, heating temperatures should be lower for the boiler to run at its higher efficiency, although this seldom happens in practice. 60degC temperature should keep most homes warm in the coldest weather with much lower temperatures being needed the rest of the year. 

Because low-temperature heat pump models are at their most efficient when the heating system temperatures run at 35-45degC, older houses will need much bigger radiators to give off enough heat as well as better insulation and potentially new windows and doors to ensure they are kept warm. Installing a high-temperature heat pump will most likely mean that you won’t need to change existing radiators, improve insulation, and replace windows and doors which can be difficult in old buildings. Though this will save you money you will need to take into consideration that high-temperature heat pumps can cost about 25% more to buy and install. 

It is important to bear in mind that to heat to higher temperatures, high-temperature heat pumps use more electricity and can therefore be more expensive to run than conventional heat pumps although cheaper than an electric panel or storage heaters. High-temperature heat pumps run on an average ratio of 1:2.5 units of electricity in, to heat out. However, like all heat pumps this figure will vary according to the season up or down. It is worth installing in a weather-compensating system which should improve efficiencies, by enabling the heat pump to work at its optimum operation for more of the time. With improvements in the technology high-temperature heat pumps are now as efficient as regular heat pumps.

A high-temperature heat pump can be the perfect solution for homes that cannot be insulated to meet current Building Regulations or better. This may be because the building is Listed, or in a Conservation Area, or is a home where the costs and risks of insulation are high, for example, homes with uninsulated solid floors, in very exposed places, or of unusual construction.

High-temperature heat pumps might also be the answer for tenanted properties that are currently using electric panel heaters. It’s less disruptive for the tenant as it will require little or no adaptation from them on how to use their new heating system. 

High-temperature heat pumps may be right for you if you need a heat pump that can produce hot water as well as space heating and you don’t have room for a hot water cylinder. 

Now is a great time to install a heat pump as the cost of installing one continues to go down and there is also help available from the government’s Boiler Upgrade Scheme. The scheme provides upfront capital grants of up to £7,500 to encourage property owners to replace existing fossil fuel heating with more efficient, low-carbon heating systems including heat pumps and biomass boilers. 

Before deciding whether a high-temperature heat pump is suitable for you, you should always seek professional advice. The Renewable Energy Hub is here to answer any questions you might have.