Ecobee Hourly Runtimes vs Sense AC Hourly Usage - 2 Stage AC Condenser

Thanks to another Sense user, I was able to take look at the Sense detection and usage data vs Ecobee data for a 2 stage AC Condenser. The main goal was to determine whether Sense sees the two different stages as different device detections or a single detection, and whether Sense is able to discern the different in power usage between the Stage 1 and Stage 2 operation. Data comes from two different sources - hourly Sense-detected energy usage for the month of Sept for all devices that have AC or A/C in their names, and hourly Ecobee runtime data ins seconds (3600 = 1 hour) for both stages of a Living Room area central air conditioner.

The chart below shows Pearson correlation analysis between each data source in a matrix form.

A few key observations:

  • Looking the Ecobee data, it looks like Stage 2 overlaps Stage 1 when it comes to runtime (they are no mutually exclusive). There are several of the highest usage hours where both are on for nearly the full hour. So Stage 1 will always be running when Stage 2 is running. That overlap will have an effect on correlations.
    Screenshot 2023-10-28 at 5.46.53 PM

  • Highest correlation (0.979 - boxes in Red) is between Sense AC 1 energy usage data and Cool Stage 1 runtimes, so we can be pretty sure that AC1 is a solid detection of the Living Room area air conditioner.

  • Based on other analysis, I also know that A/C 2 is a solid detection (0.952 correlation) of a second air conditioner in the user’s Bedroom. So I’ll leave A/C 2 out of the comparisons.

  • Now we get into the the tricky stuff - AC 1 energy correlates somewhat closely with Cool Stage 2 runtime (0.669 - boxes in Green), though there are lots of hours where AC 1 is substantial while Stage 2 is zero (that’s when the AC is running in Stage 1 mode).

  • There’s also somewhat good correlation (0.584 - Blue Boxes) between Stage 1 and Stage 2 runtimes because Stage 1 is alway on and longer than Stage 2 when Stage 2 is on.

  • The graph in the red box shows one more interesting thing - the rough energy transition between Stage 1 and Stage 2. Since Stage 1 is always on when Stage 2 kicks in, we see line with a “knee” in it. It looks like Stage 1 uses about 3.6kW (magenta slope) but shifts to 5kW (orange slope) in Stage 2.

  • The A/C Condenser pump shows some correlation with A/C 2 but not with either of the Living Room runtimes, so I think that’s probably related to the Bedroom AC unit (A/C 2) as well.

The conclusion is that Sense sees this 2 stage AC unit as a single detection that actually varies depending on stage, and that Sense is doing a pretty good job of detecting AC usage in this case.

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