Sense stops reporting Window AC mid-cycle

Sense has detected one of my window AC’s. It reliably reports when it turns on. However, it seems to only report about two minutes of the run time then just stops on the power meter for the device until it cycles again. Is this something that will clear with more analysis on the device over time? Three cycles shown below in the first picture and a zoom on one of the cycles in the second.

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How long is the actual run cycle ? What’s does the corresponding view on your Total C
Usage Power Meter look like ?

It usually runs three to 5 minutes. It appears it is only registering the compressor, not the blower fan. The unit is rated to run at 540 watts and in the power meter when running it is 420. I have turned the fan only on and off on the unit and it accounts for roughly another 100 to 110 watts on its own. The total C meter jumps the full 530 - 540 when the unit turns on. I have left the unit running in cool with the fan on all the time and it show as off when the compressor is not running, and the bubble pops up when the compressor turns on. Just odd that it drops off exactly two minutes into the cycle and the compressor is still stunning.

Just to be clear on how Sense functions, it will usually detect the compressor separately from the blower motor, even if they are the in same device, because they each have different on and off signatures. In most AC units, the blower will start before the compressor and run for a while after the compressor is done. Hopefully Sense will pick up your blower motor over time and you’ll have the option of combining the two.


This may give you (us) a little insight.

Here is Sense native detection (orange) overlaid with smartplug detection on the same AC unit at the same time (as close as I could get it at least, sorry about the blurry bits).

Here we see, in Sense’s interpolated signature for the AC, that there is ramping, at the end of which it makes an assumption about the average usage (hence the flattened plateau in the wave) until the “switch-off” signal is detected. You can clearly see the blower still operating in the smartplug (blue) waveform.

Sense is assigning (from overall usage) your AC’s signature through that initial ramping and then getting confused and assuming a “switch off” signal after a couple of minutes.

A guess: the ramping is a little longer that “expected”? The end of the capacitor charge cycle is throwing things? Sense (@RyanAtSense): does this potentially imply something about the state of the unit?


Nice overlay… It looks like Sense is doing very close to what I would expect in the case of your AC unit, @ixu. It’s detecting the on/off of the compressor as a single device, while treating the blower baseline separately. One can’t tell precisely from this overlay, but it looks like Sense is getting the overall compressor waveform right in both the time and power dimensions, with a little bit of clipping on the top of the waveform.

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I’d love to report that it’s that consistent all the time but the reality is that Sense struggles.
It seems to do well with the frequent cycling (prior post) but when the unit is on and there is limited thermostatic switching, it’s disappointing.

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We’d love to dig a bit further into what you’re seeing. Could I have the DS team take a look?


I was trying to do similar to you - tried to find hours of my downstairs AC unit power consumption where Sense missed detections. I don’t have my central AC on a smartplug like you do so it’s a bit harder. I do have my furnace blowers (actually the whole furnace) on smart plugs plus my Ecobee command data, so I do have a couple proxies to use.

For my solid AC3 detection of my downstairs AC compressor, Sense is spotting about 207 out of 238 on hours, missing 31 hours. It also looks like it could be incorrectly spotting compressor usage as on in about 7 hours. I say “could” because the compressor can extend and stop runs independently from the thermostat commands and furnace fan, under certain conditions.

Those 207 detection usage data points match up fairly well with the Ecobee runtimes and the furnace fan power consumption.

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