A new generation of high-temperature heat pumps (HTHPs) is now available, offering a low-carbon heating alternative without the disruption often associated with heat pump retrofits. Capable of delivering flow temperatures up to 80 °C, these systems are suited to both domestic and commercial buildings.
Flow Temperatures That Match Boilers
Most traditional heat pumps operate at 35–55 °C and work best in new or well-insulated buildings with oversized radiators or underfloor heating. High-temperature models, by contrast, can deliver 65–82 °C flow temperatures, making them ideal for older homes, heritage buildings, schools, offices, and care homes that still rely on standard radiators or conventional pipework.
Ideal for Retrofit
One of the biggest advantages of HTHPs is that they can often be installed without replacing radiators or upgrading internal pipework, significantly reducing cost and disruption. For both domestic and commercial sites, this means the ability to cut emissions and energy costs without rebuilding the heating system from scratch.
Efficient, Even at High Temperatures
While heat pumps are typically more efficient at lower temperatures, modern high-temp models still achieve COPs of 2.0–3.0—meaning they produce 2–3 times more heat than the electricity they consume, even at boiler-matching temperatures. Most include weather compensation to reduce flow temperature when conditions allow, improving seasonal efficiency.
While heat pumps generally perform better at lower flow temperatures, Clade’s Elm R‑290high-temperature heat pump achieves a Seasonal COP (SCOP) of around 2.0 when operating at 80 °C flow and 70 °C return conditions .This demonstrates that modern HTHPs can remain twice as efficient—or more—than the electricity they consume, even while delivering boiler-style temperatures.
The Daikin Altherma 3 H HT has a Coefficient of Performance (COP)that varies with operating conditions:
At 7 °C ambient / 35 °C flow: COP ≈ 4.86
At 7 °C ambient / 45 °C flow: COP ≈ 3.70
When raising the flow temperature to 65–70 °C (closer to boiler levels), performance naturally drops. Although Daikin doesn't explicitly publish COP at A‑2 °C/W65, we can estimate it would be slightly lower than the 45 °C flow COP. Based on typical high-temperature degradation patterns—and given a COP of 3.70 at 45 °C flow—it’s realistic to expect a COP around 3.4–3.6 under 65–70 °C flow conditions.
What do you mean COP?
COP stands for Coefficient of Performance. It's a measure of efficiency for heating and cooling systems like heat pumps.
In simple terms:
COP = Useful heating (or cooling) output ÷ Electrical energy input
So, a COP of 3.0 means that for every 1 kWh of electricity a heat pump uses, it provides 3 kWh of heat.
Natural Refrigerants for Long-Term Compliance
Modern high-temperature systems use low-GWP (Global Warming Potential) refrigerants like:
CO₂ (R‑744) –Non-flammable and climate-friendly (GWP = 1), capable of stable high-temp performance.
Propane (R‑290) –Highly efficient and widely used in the latest UK-manufactured units.
These refrigerants offer strong performance while complying with tightening F-gas regulations, making them a future-proof choice for both homes and commercial properties.
UK-Made High Temp Heat Pumps
Several British manufacturers are now producing HTHPs that are suitable for a range of applications:
Clade Elm (R‑290) –UK-built unit delivering 80 °C flow, ideal for replacing gas boilers in offices, or small commercial buildings with minimal system changes.
Clade Larch(Cascade R‑290/R‑600a) – Achieves 82 °C flow with a cascade setup, suitable for commercial properties needing boiler-level performance with greener credentials.
Pure Thermal high-temp range – UK-designed air-to-water systems designed for domestic and small commercial retrofit, using natural refrigerants and offering flow temperatures of up to 75 °C+.
Things to Consider
While high-temperature heat pumps offer significant benefits, they do come with challenges. In the UK, electricity is currently around four times more expensive than gas per unit, meaning a heat pump typically needs a COP above 4 to achieve lower running costs than a gas boiler. However, COP decreases in colder weather and at higher flow temperatures—precisely when heating demand is highest. As a result, winter running costs for ASHPs may exceed those of gas, especially in less efficient systems. Focusing on cost savings alone can therefore be misleading. That said, grid-connected ASHPs typically emit three to four times less carbon than gas boilers, thanks to both their higher efficiency and the rapidly decarbonising UK electricity grid. In fact, the government aims for a net-zero carbon electricity system by 2035, which will make heat pump carbon savings even more significant in the years ahead.
Installation costs can also be substantial. The Boiler Upgrade Scheme provides grants up to £7,500 but is currently only available to domestic properties in England and Wales. Heat pumps also require external space for the unit, which may not be suitable for all properties, and some models can produce noticeable noise—especially at higher output. Finally, questions remain about whether the UK’s electricity grid can support mass uptake of heat pumps alongside EVs and other electrification demands, particularly in older or rural areas with limited capacity. Careful planning and site assessment are essential. This is where the experts at What’s the Payback come in. Please contact us to speak to arrange a no obligation chat.
