COP variation with output temperature
Pump type and source Typical use 35 °C
(e.g. heated screed floor)
45 °C
(e.g. heated screed floor)
55 °C
(e.g. heated timber floor)
65 °C
(e.g. radiator or DHW)
75 °C
(e.g. radiator and DHW)
85 °C
(e.g. radiator and DHW)
High-efficiency air source heat pump (ASHP), air at −20 °C[5] 2.2 2.0
Two-stage ASHP, air at −20 °C[6] Low source temperature 2.4 2.2 1.9
High efficiency ASHP, air at 0 °C[5] Low output temperature 3.8 2.8 2.2 2.0
Prototype transcritical CO
2
(R744) heat pump with tripartite gas cooler, source at 0 °C[7]
High output temperature 3.3 4.2 3.0
Ground source heat pump (GSHP), water at 0 °C[5] 5.0 3.7 2.9 2.4
GSHP, ground at 10 °C[5] Low output temperature 7.2 5.0 3.7 2.9 2.4
Theoretical Carnot cycle limit, source −20 °C 5.6 4.9 4.4 4.0 3.7 3.4
Theoretical Carnot cycle limit, source 0 °C 8.8 7.1 6.0 5.2 4.6 4.2
Theoretical Lorentzen cycle limit (CO
2
pump), return fluid 25 °C, source 0 °C[7]
10.1 8.8 7.9 7.1 6.5 6.1
Theoretical Carnot cycle limit, source 10 °C 12.3 9.1 7.3 6.1 5.4 4.8