One of the reasons that sense under reports is because realistically it only detects the on sign (large draw) then flatlines for an average consumption during that period and the off sign (drop in watts eq or greater than the average consumption probably +/- some threshold).
Realistically the compressor slowly builds over the entire runtime. And the “off” sign is usually confused with other items.
Consider the following. This device is taken from a shelly em reporting to senselink then to sense. This will likely be the best representation of the water heaters actual use. Shelly EM numbers are nearly identical to the EcoNet app.
Compare that to the sense detected device. There is obviously a large portion not detected due to the ramp.
