Guide: High Temperature Air Source Heat Pumps

In Summary: Our High Temperature Heat Pump Guide

Our guide to high temperature heat pumps is an approximate 10-minute read. So, if you’re short on time, bookmark this page for later, and read this summary instead…

Air source heat pumps work well in highly efficient homes, as well as with larger radiators than you’d use with a gas boiler. This allows them to operate at flow temperatures of 40-55°C, rather than that of 65-70°C for a gas boiler. 

Units such as the Vaillant aroTHERM Plus can achieve up to 75°C, thanks to their high quality refrigerant (R290). This removes the need for an immersion heater, which can be expensive to run. 

Even though high temperature units are efficient, expect an decrease in efficiency of approximately 9.2% for every 5°C increase in flow temperature; running costs will increase in line with this drop in efficiency.

Installation costs match that of standard heat pumps; approximately £10,000 for an average property. That said, a £7,500 Boiler Upgrade Grant is available for most households, reducing the average cost to approximately £2,500.

And finally, some of the best high temperature air source heat pumps available in the UK (70°C flow temperature or higher) include:

• Vaillant aroTHERM Plus
• Daikin Altherma HT
• Samsung HTQ
• Viessmann Vitocal

Ready to get your new air source heat pump fitted? Use our clickable tool here. That’ll suggest the best unit for your property based on the details you give us.

Air Source Heat Pump Flow Temperatures

Flow temperatures for heat pumps are much lower than that of gas boilers. Whilst a typical gas boiler might be set to around 65-70°C, air source heat pumps are typically set somewhere in the 40-55°C range.

These lower temperatures are how air source heat pumps gain efficiency when compared to gas boilers. Typically, a heat pump will operate at 300% efficiency or higher, compared to that of 94% or lower efficiency for a gas boiler. 

For a heat pump to work, you need a well insulated home and much larger radiators than usual. They’ll work “low and slow” rather than at full power as a gas boiler would. 

But for those that don’t have a highly efficient property, a high temperature heat pump could be the answer. 

A unit such as the Vaillant R290 aroTHERM Plus has a maximum flow temperature of 75°C, much higher than the average heat pump. Put simply, this will keep even inefficient houses warm, whereas a standard heat pump wouldn’t.

How A High Temperature Heat Pump Works

Air source heat pumps extract air from outdoors, using any heat to warm refrigerant in your system. It's then compressed which further increases its temperature. Next, it transfers that heat to your heating system, and the whole process starts again. 

The important part here is the refrigerant that's used. The most efficient refrigerants that work best with high temperature heat pumps include R290 and R32. 

As you can see in our list of the best air source heat pumps, all 4 of our top picks use R290 or R32 refrigerant:

• Vaillant aroTHERM Plus (R290)
• Samsung EHS HT Quiet (R32)
• Ideal Logic Air (R32)
• Grant Aerona (R32)

One disadvantage of standard low temperature heat pumps is they need a direct electric immersion. The electric immersion heats water to a temperature that’s safe. This protects households from the risk of legionella, a bacteria that grows in water and soil.

Naturally, using an electric heat of any kind (an immersion in this case) isn’t energy efficient. A high temperature heat pump such as the Vaillant aroTHERM Plus R290 can heat water to 75°C, without the need for a direct electric immersion. 

So, whilst it loses some efficiency due to working at higher temperatures, it saves energy by not using a direct electric immersion.

Installation Costs

The cost to install a high temperature air source heat pump won’t vary much from a standard heat pump. Expect costs including labour to be in the region of £10,000 for an average 3-bed semi-detached property. 

This assumes that you’ll be purchasing a pump from a leading brand. To reduce the overall cost, you’ll be able to get a £7,500 discount on your installation by using the Boiler Upgrade Scheme, a popular government heat pump grant. 

Whilst there are cheap no-name brands out there, we find that durability wise, long lasting heat pumps come from a few top brands. 

Our list of the best heat pump brands that offer their heat pumps with a long warranty (up to 7-years), include: 

• Grant 
• Ideal Heating
• Samsung
• Vaillant
• Viessmann 
• Daikin 
• Dimplex 
• Mitsubishi
• LG
• Worcester Bosch

Remember, just because you have a heat pump with a high flow temperature, doesn’t mean it needs to be running at full power constantly, but the option is there. 

And, that’s why on our list of top rated heat pumps we recommend the likes of the Vaillant aroTHERM Plus 7kW. It has the ability to work at 75°C, compared to the average heat pump that can only manage 55°C.

Check out our clickable heat pump page here. Within a few minutes you’ll have fixed prices on-screen for high temperature heat pumps that are most suited to your property.

Or, if you’d prefer to dive deeper, read our guide covering air source heat pump installation costs here. 

Running Costs & Efficiency

The running costs of high temperature heat pumps are higher than low temperature heat pumps. The higher the flow temperature, the more it’s going to cost. For every 5°C flow temperature increase, there’s approximately 9.2% loss in efficiency.

There are dozens of variables that affect the exact running costs of a air source heat pump including: 

• The temperature you set your thermostat to
• Size and efficiency of your radiators
• Type and quality of loft and cavity wall insulation
• Size of your property
• The list goes on…!

However, below we can see just how drastic the changes in efficiency of your heat pump are as flow temperature increases. 

For this we’ll take the Seasonal Coefficient of Performance (SCOP) rating at certain levels. 

SCOP is a measure of how much heat your heat pump produces, for every 1kWh of electricity used. If a heat pump has a SCOP of 2, it produces 2kWh of heat for every 1kWh of electricity consumed.

Below are the SCOP ratings for the Ideal Logic Air 8kW, one of the most efficient heat pumps on the market.

As you can see, the SCOP rating drops significantly for each 5°C increase in temperature, we see a drop of 9.2% (on average) in heat output and therefore, efficiency.

Advantages & Disadvantages

If you’re deciding whether you get a high temperature heat pump fitted, it’s important to understand both the advantages and disadvantages.

Advantages

Installation Costs

The cost of installing a high temperature heat pump is the same as a standard air source heat pump. The only difference in price comes down to the exact unit you choose; each manufacturer and specific model differs in price compared to the next.

And these installation costs are similar to a gas boiler, when you account for the £7,500 government Boiler Upgrade Scheme grant. You can get heat pump prices on-screen using our clickable form.

Highly Efficient Compared To Gas Boilers

Even when run at its maximum flow temperature, an air source heat pump is much more efficient than a gas boiler. 

Gas boilers (even new A-rated ones) only hit around 94% efficiency. As you can see from our table above, a pump such as the Ideal Logic air can work at between 396% efficiency (at 50°C), and 509% (at 35°C). 

Suitable For All Types Of Properties

The biggest advantage of heat pumps with high flow temperatures is their property suitability. 

Typically, standard heat pumps are only suitable for homes with extremely high efficiency; they’ll have quality cavity wall and loft insulation. 

However, high temperature heat pumps can work in less efficient properties, and even those that haven’t had radiator upgrades.

Disadvantages

High Flow Temperature = High Running Costs

Whilst modern heat pumps can work efficiently at high temperatures, they’re still not going to be working at their most efficient. The lower the flow temperature you can use, the more efficient your heat pump is going to be. 

Choose to run your heat pump at its maximum temperature? Your electric bill is going to feel the pinch. 

Property Upgrades

Whilst the fact high temperature pumps can be used in almost any property is an advantage, to reach maximum efficiency, upgrades will be needed. 

To lower your electricity bill to its absolute minimum you’ll need property upgrades such as: 

• Cavity wall insulation
• Loft insulation
• Larger radiators; these allow a heat pump to heat your home even when set at a low flow temperature

Noise

Heat pumps can be noisy. The harder they work, the noisier they are. And when working at full-tilt at maximum flow temperature, this is when they’re going to be at their loudest. 

However, there are plenty of high temperature pumps that work at ridiculously low noise levels; lower than standard heat pumps in some cases. 

As an example, the Mono HT Quiet Outdoor operates at up to 70°C, whilst its 4-setting noise control means it can produce as little as 35d(BA).

The Best High Temperature Heat Pumps

The best high temperature heat pumps come from leading heating and ventilation brands. 

We stress the importance of warranty here. Whilst there are cheap heat pumps available with a low warranty (typically 2-years), we’d be aiming for a warranty of 7-years where possible.

Whilst there are dozens of brands offering efficient units, not all of them offer high temperature pumps. Some of our top picks include the likes of the: 

• Vaillant aroTHERM Plus
• Daikin Altherma HT
• Samsung HTQ
• Viessmann Vitocal

But which is the right one for your property? 

Take out the guesswork as well as the confusion. Use our clickable property spec page here. Within a couple of minutes we’ll have the most suitable pumps listed on-screen, including a fixed price.

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