I can’t believe it’s taken me 6 months to notice but I have realised my heatpumpmonitor graph reports electricity input to 1 decimal place but heat energy only to a whole integer, e.g. no decimal places. I know that greater accuracy is possible because clicking “Show Detail” gives electricity and heat energy to 3 decimal places.

I have had a brief look in emoncms and around this forum but can’t find a straightforward way to change how the heat energy is reported. Ideally this would be to 1 decimal place also.

When in the heating season it barely makes a difference to COP but now I am just doing my hot water it can make quite a big difference. Say I use 1.0 kWh of electricity, I could generate 2.5-3.4 kWh of heat and emoncms/heat pump monitor would report that as 3 kWh and give a COP of 3.

Looking at your data, it seems that the daily heat output really is quantized to whole integers. How is the heatmeter_Energy feed being collected? Where does it come from? It’s possible that this data is only provided to you in whole numbers.

You might get more precise data if you took the heat power input (watts) and used the Power to kWh process step and log to a new feed. The numbers might not match exactly, but you’ll have more decimal places.

The quantisation error on most heat meters is 1 kWh (always rounding DOWN to the nearest kWh)

Some can be configured for 0.1 kWh but that’s a big error.

The quantisation error for “power” on many heat meters is 100W. Again always rounding DOWN to the nearest 100W.

The flowrate is usually rounded to the nearest 0.001 m3/hr (1 litre per hour); so taking flowrate multiplied by (supply-return temperature) then multiplying this by time will give you the most granular result across heat meter brands.