Looking for non-invasive indicators of drops in efficiency on my heat pump system. Intuitively, it feels like I could look at the average runtime at each degree over time. I know other factors could affect this number but average trends over time should probably correct for that. However, a quick GPT convo shows that looking at my power draw (kw) may also be a good proxy? I used my power draw (compressor + air handler) and rated heating capacity (Btu converted to kw) to calculate a live unit and system COP (4.7 and 4.1 respectively). If the power draw goes up, then the COP goes down. Is this something I could use to ID dirty coils, loop issues, etc. early? Maybe even better time my maintenance calls based on performance?

I have found no correlation to freon level to power draw....fyi...thus don't think you will see anything in power draw unless you can chart it over a long period. Mine varies a couple amp normally.

I would chart entering water temp and leaving water temp to air handler leaving and entering...there are some super heat calculations that might be what you are looking for if you connected to the freon pressure.

Is it a two stage unit? Ecobee therms give some data on run times to outside temp you might like.