Moved from the main thread. Picking up from earlier posts on other trials:
A new report out today Energy Systems Catapult: https://es.catapult.org.uk/news/heat-pumps-shown-to-be-three-times-more-efficient-than-gas-boilers
Looks like heatpumpmonitor.org systems are still on the upper end of the systems seen in these studies. Though interestingly there are quite a few systems with a COP of 3.5-4.0 in the scatter graph below:
Here are some of the key tables, summarising the findings:
Air source heat pumps:
Another interesting finding that the newer refrigerants are out performing R410a, not something we have enough data points on yet to be able to make any inference.
Coldest day performance
The observed heat pump efficiency (COP(H4)) decreased as the external temperature
decreased. The median COP(H4) on the coldest day (mean temperature -0.4°C) was:
• Median coldest day COP(H4) = 2.44; IQR = [2.20, 2.70]; n=484
SPF H2 Scatter
There are quite a few systems here that cover the range we are seeing!