Performance Gap Between Ratings and Real-World Use: Enhancing Trust Through Standards and Innovation
Air-to-air heat pumps are considered an environmentally friendly alternative to conventional fossil fuel heating systems. They use a small amount of electricity to operate a compressor that extracts heat from outside air to provide heating or cooling. Their efficiency is typically measured by the Coefficient of Performance (COP) and Energy Efficiency Ratio (EER), with seasonal counterparts—Seasonal COP (SCOP) and Seasonal EER (SEER)—accounting for variations throughout the year.
Under EN 14825, SCOP is calculated based on heating demand curves across three climate zones. According to EU Ecodesign regulations, a SCOP of at least 3.4 and a SEER of at least 3.6 is required. In practice, high-performance products have demonstrated SCOP values ranging from 3.8 to 4.8 and SEER values between 4.9 and 8.7, corresponding to energy labels rated A to A+++.
However, in-situ performance—actual performance under real-world conditions—often falls below these rated values. Field measurements have shown SCOP figures closer to 2.8, influenced by installation environment, pipe length, and usage patterns. This discrepancy has also been reported in studies by Delta-EE and Arup.
To address this gap, alternative evaluation methods such as energy balance approaches and control-variable compensation methods have been proposed and are under consideration for future updates to EN 14825.
Regarding actual energy consumption, annual usage figures have been reported in the range of 944–2438 kWh for heating and 189–559 kWh for cooling, varying by unit size and operating period.
A study from Denmark showed that switching from electric heating to air-to-air heat pumps resulted in a 26% reduction in electricity use. However, the benefit was partially offset by a rebound effect, where improved comfort led to longer heating hours, thus lowering the expected energy savings.
Key Terms
- COP / SCOP (Coefficient of Performance / Seasonal COP): Metrics for assessing heating efficiency; SCOP reflects real-world, year-round performance.
- Energy Label (A+++ to G): Efficiency rating system based on SEER and SCOP, helping consumers choose high-performance appliances.
- Rebound Effect: A phenomenon where improved efficiency leads to increased usage (e.g., longer heating hours), reducing the net energy savings.
