High Temperature Heat Pumps | Are They Worth It?

When choosing a heat pump for your home, you may have considered high temperature heat pumps as a replacement for your old fossil-fuel boiler. However, it’s essential to understand their limitations compared to more efficient low temperature heat pumps.

What Is a High Temperature Heat Pump?

High temperature heat pumps heat water to temperatures similar to traditional fossil fuel boilers (around 60°C to 80°C). This often eliminates the need for costly upgrades, such as new radiators, during installation.  

While avoiding infrastructure upgrades may seem appealing, this advantage is short-lived. High temperature heat pumps consume more energy to heat water to higher temperatures, resulting in increased electricity usage and higher costs.  

Another factor driving their popularity is the misconception that low temperature heat pumps cannot effectively heat a home year-round. However, this is not true and often misleads consumers into choosing high temperature heat pumps.  

High Temperature vs. Low Temperature Heat Pumps  

Most heat pumps can heat water for taps and showers to temperatures similar to gas or oil boilers (around 60°C to 70°C), even though such high temperatures are unnecessary, as anything above 45°C at the point of use can cause scalding.  

The main difference lies in their operation: low temperature heat pumps heat water for radiators or underfloor heating at 35°C to 55°C, while high temperature heat pumps operate at 60°C to 80°C. This makes low temperature heat pumps more efficient and cost-effective to run.  

Additionally, low temperature heat pumps are, on average, 10% cheaper to buy. However, if new radiators are required for their system, the upfront costs may become comparable.  

Advantages and Disadvantages of a High Temperature Heat Pump  

High temperature heat pumps offer some short-term benefits, but their drawbacks should be carefully weighed before deciding.  

Advantages  

- Versatility: They produce hot water at both low and high temperatures, making them suitable for showers, baths, and general heating. Storing water at higher temperatures can also increase hot water availability when using mixer taps.  

- Compatibility: High temperature heat pumps integrate well with existing heating systems, reducing the need for upgrades like new radiators or added insulation.  

- Quick Installation: With fewer infrastructure modifications required, installation is faster than for low temperature systems.  

- Immediate Heat: They provide rapid heating for periods of high demand.  

Disadvantages  

- Energy Intensive: Reaching high temperatures requires more energy, resulting in higher consumption and increased operating costs.  

- Environmental Impact: The higher energy demand can lead to greater carbon emissions, offsetting some of the environmental advantages of renewable energy.  

- Upfront Costs: High temperature heat pumps are approximately 10% more expensive than low temperature models.  

- Long-Term Expenses: Despite immediate benefits, the higher energy costs can make them less economical in the long run.  

Can a High Temperature Heat Pump Be More Efficient Than a Low Temperature Heat Pump?  

Some sources suggest that high temperature heat pumps are as efficient as, or more efficient than, low temperature models due to superior refrigerants like R290 or R32.  

While this may have been true in the past, modern low temperature heat pumps now use the same efficient, eco-friendly refrigerants. Consequently, high temperature heat pumps are generally less efficient because they require more energy to heat water to higher temperatures.  

The difference in efficiency can be highlighted through SCOP (Seasonal Coefficient of Performance) values:  

- High Temperature Heat Pumps: With flow temperatures of 60°C to 80°C, SCOP typically ranges from 2 to 2.5, meaning they generate 2 to 2.5 units of heat for every unit of electricity used.  

- Low Temperature Heat Pumps: Operating at flow temperatures of 35°C to 55°C, these pumps achieve SCOP values above 4.7, making them four times more efficient than gas or oil boilers and twice as efficient as high temperature heat pumps.  

How Does a High Temperature Heat Pump Work?  

High temperature heat pumps use the same advanced technology as standard heat pumps, efficiently harnessing thermal energy to heat your home and water. However, achieving higher water temperatures involves four key differences:  

- Enhanced Components: Equipped with robust compressors and heat exchangers, high temperature heat pumps handle higher temperatures and pressures, efficiently transferring heat from the environment to the water system.  

- Increased Refrigerant Capacity: They use refrigerants with higher critical temperatures and greater heat-carrying capacities, enabling effective operation at elevated temperatures.  

- Optimised Control Systems: Advanced control systems monitor and adjust parameters like compressor speed, refrigerant flow, and defrost cycles to maintain optimal performance and efficiency.  

- Supplementary Heating Elements: Some models include additional heating elements, such as electric resistance heaters or gas-fired boilers, to raise water temperatures during peak demand or extreme weather conditions.  

When Is a High Temperature Heat Pump the Right Option?  

A high temperature heat pump may be suitable for homes that prefer to retain their existing infrastructure rather than upgrading to accommodate a low temperature heat pump.  

However, while it may offer initial cost savings, the long-term running costs are typically higher than those of a low temperature heat pump. Consider exploring heat pump costs to determine if it’s the best choice for your needs.