When is a heat pump most efficient?

Key takeaways:

• Air source heat pump efficiency ranges from about 150% to 400%
• Their efficiency is highest when the outside temperature is between -3°C and 10°C
• They can work efficiently at temperatures as low as -25°C, coming in at about 150%

Heat pumps provide an innovative, efficient way to heat your home by transferring heat instead of generating it. This approach makes them environmentally friendly and cost-effective compared to traditional heating systems. While they are always highly efficient, their performance can fluctuate with outdoor temperatures.

Air & water temperatures

Outdoor air temperatures can affect the efficiency of air source heat pumps. They perform best in milder conditions, typically between -3°C and 10°C, achieving a Coefficient of Performance (COP) around three, meaning they can produce three units of heat for every unit of energy used. As outdoor temperatures drop, the system requires more energy to extract heat from outdoor air, which can lower the overall efficiency.

Water flow temperature is another key factor. Heat pumps are most efficient when water is heated to 35°C–45°C, making them most efficient when paired with larger radiators.

System design & insulation

The efficiency of a heat pump depends on its design and the conditions of the home. Aira’s Solution Designers use detailed data to calculate your heat loss and design you a highly efficient heating system to meet your needs. Modern systems, like the Aira Heat Pump, can work efficiently in temperatures as low as -25°C. Sufficient insulation will also help your home retain heat better, reducing the pump’s workload.

Understanding efficiency ratings

Heat pumps can produce over four times more heat energy than the electricity they consume, making them highly efficient. Efficiency is measured using metrics like the Seasonal Coefficient of Performance (SCOP), which assesses performance across varying conditions throughout the year.

Cold weather performance

Air source heat pumps remain effective even in freezing conditions, extracting heat from the air to warm your home. While efficiency decreases as temperatures drop, they are still more energy-efficient than traditional gas boilers, which typically operate at 85% efficiency. During extreme cold, many heat pumps include a boost function to provide additional warmth without excessive energy use.

Paired with underfloor heating or larger radiators, heat pumps perform even better, distributing heat efficiently at lower temperatures.

Sizing, installation & smart features

Proper sizing is crucial for heat pump efficiency. An oversized system cycles too frequently, wasting energy, while an undersized system struggles to maintain warmth, increasing energy use. Our designers and technicians will make sure you get the system you need to ensure maximum performance.

Smart thermostats, like the Aira Thermostat, can further enhance efficiency by allowing precise control and optimising temperature settings based on your schedule. Strategic placement of the outdoor unit, away from strong winds or snow buildup, also improves performance.

Conclusion

Heat pumps offer a sustainable, cost-effective heating solution that reduces your carbon footprint while keeping your home comfortable. With the right setup, they provide reliable, energy-efficient heating year-round.