Made another mistake above in the compressor size corrected comparison, I plotted oversizing factor vs the wrong SPF/COP column (DHW not combined!). Here’s the corrected plot, that does actually show somewhat of a trend, though again probably one to be very careful with as the visual trend is influenced strongly by your system @matt-drummer with it’s extra large radiators giving the SPF/COP near 5 and the Shirehampton 6kW (8kW compressor) with 1.5 kW heat demand. A system with 1.5x oversizing factor could easily get a much lower COP if the emitter system dictated a much higher flow temperature of course.
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