From near the top of the actual 'research' paper (BTB called 'Coming in from the Cold' - note quite the academic tone. Will the research group's next paper be titled 'Tinker Tailor Soldier Plumber'?):

Heat pump efficiency is measured by the device’s coefficient of performance (COP), the ratio of the useful heat outputted to energy consumed. Typical COP values for heat pumps lie in the range of 3–6, indicating that 3 to 6 units of heat are created from each unit of electricity used. A year-round average COP of 3–4 is common for household applications.

"outputted" ??? I can't believe I readed that...

"3 to 6 units of heat are created..." now they think they are God. I'm outa here...

PS @jamespipe, not having a go at you, thanks for posting it

Posted by: @cathoderay

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From near the top of the actual 'research' paper (BTB called 'Coming in from the Cold' - note quite the academic tone. Will the research group's next paper be titled 'Tinker Tailor Soldier Plumber'?):

Heat pump efficiency is measured by the device’s coefficient of performance (COP), the ratio of the useful heat outputted to energy consumed. Typical COP values for heat pumps lie in the range of 3–6, indicating that 3 to 6 units of heat are created from each unit of electricity used. A year-round average COP of 3–4 is common for household applications.

"outputted" ??? I can't believe I readed that...

"3 to 6 units of heat are created..." now they think they are God. I'm outa here...

PS @jamespipe, not having a go at you, thanks for posting it

A typically pro-heatpump Guardian article but most of the data used in the study is from A2A systems.  

Posted by: @kev-m

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most of the data used in the study is from A2A systems

And the authors are hardly without an agenda. From their front page: "The Regulatory Assistance Project (RAP)® is an independent, non-partisan, non-governmental organization dedicated to accelerating the transition to a clean, reliable, and efficient energy future." The study also has other flaws. It is a quasi meta-analysis (a meta analysis is a 'study of studies') and in any such study the inclusion/exclusion criteria for the inclusion of studies, as well as the thoroughness or otherwise of searching for studies, is of the utmost importance, and this is barely covered, if at all. How do we know they did not just cherry pick the studies that best made their case (a 'here's the conclusion now where is the evidence' study)? On the type of heat pump included, I am not sure it is even possible to say what the A2A to A2W ratios was, though both were included (might be possible by looking at all the sources, but I doubt it, and anyway, life is too short). 

This chart is also rather odd/intriguing:

It looks as though the UK had the highest (in this context, nearest to zero) minimum temp, yet the median COP (I presume the dotted lines in the plots are the medians) is one of the lowest, and there are a lot of what I presume are outliers. More questions than answers...

It has sadly become the case that many science hacks just recycle journal press releases, without engaging the little grey cells.