Inconsistent Math - Bug in Total Power Calculation?

Technical Questions
#1

I have my Sense, and added 2 CTs for DCMs and multiple TP-Link KP115.

  1. One of the CTs is mounted on the dishwasher’s breaker, and one KP115 is used on the kitchen fridge.
  2. Whenever the fridge kicks in, two bubbles are displayed, one from the KP115, the other apparently because Sense has already identified the fridge.
  3. Likewise, whenever the dishwasher is running, two bubbles shw up, one from the specific CT/DCM, the other simply named ‘Dishwasher’.

Now, if I take the powers (Watts) from all the bubbles and add them up, I get a number that’s very close (within 34 Watts) to the total displayed in the top right corner. This is rather peculiar/odd as both the fridge and dishwasher should NOT be counted twice. Furthermore, the Total Watts (displayed in top right corner) should be the value measured by the main CTs. This leads me to believe that there is a bug here as the total power should NOT be the sum of all the bubbles, especially when there are duplicates. Under ideal conditions YES, the total is the sum of all bubbles … but if there are duplicate bubbles, then the calculation falls apart.

Thoughts? What am I missing?

I’d post a screenshot, but not sure how to do that yet.

#2

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#3

Thank you … I was looking for a paper clip, but could not find it.

#4

2 posts were split to a new topic: Energy bill calculation inaccurate

#5

As you suggest, in a correct installation, the Total Consumption, DCM and smart plug data are all coming from direct measurements. That the device direct measurement bubbles plus the bubbles for their corresponding erstwhile detections add up to the Total Consumption is simply coincidence. You should also have an Always On and Other bubble at least most of the time, so it’s likely that any double counted detections are actually being subtracted out of Other. One other note - if your detected total including Always On, DCMs, smart-plugs and native detection is greater than the Total Consumption you won’t see a negative Other Bubble, it will just disappear, masking many cases of double counting.

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#6

Thank you Kevin. It seems my original post is not very clear. Imagine this, I have 4 bubbles on my screen:

  1. Bubble 1 - Always On - 600 W
  2. Bubble 2 - Other - 900 W
  3. Bubble 3 - Fridge - 250 W (detected by Sense)
  4. Bubble 4 - Fridge - 250 W (from Smart Plug KP115)

Total (Text In Upper Right Corner) - 2000 W

Now, if I add up all the bubbles, I get 2000 W (makes sense). However, Bubbles 3 & 4 are exactly the same thing (double reporting). That means, the total should really be 1750 W … and NOT 2000 W.

I have seen the above behavior many times, with both my fridge (on a smart plug) and my dishwasher (on dedicated CT/DCM). I agree fully with you that the sum of the bubbles should match the total number in the upper/right corner … but NOT if some of the bubbles are duplicates of one another. That is why I suspect the total number in the top right corner is calculated from the sum of the bubbles … whereas it should be measured (from the 2 main CT sensors)

Makes sense now ?

#7

Ah, thanks for breaking this down @drjb. Very helpful.

When you set-up a device with a smart plug (or dedicated circuits), you have to tell Sense what’s being monitored or it can double-count devices.

To do this, simply:

  1. Click on your Fridge (the device connected to the smart plug)
  2. Navigate to ‘Device Settings’ via the gear icon in the top right hand corner
  3. Click on the ‘Manage’ tab
  4. Under ‘Smart Plug’, click “What’s plugged into this?”
  5. Select the Fridge device detected by Sense
  6. Click ‘Save’ in the top right-hand corner

You should see this issue resolved once you complete the steps above.

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#8

@drjb, You’re missing something here. The Other bubble adjusts up and down to fill the gap, so the bubbles always add up to the Total Consumption. Other is a computed bubble, not a measured bubble. It is computed as Total Consumption minus all the detected and measured bubbles. So even if some devices are double counted, Other just shrinks commensurately.

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#9

Bingo! Yes @kevin1 you’re right. The one thing I did not catch is that, whenever I see the dual bubbles, the ‘Other’ bubble is somehow missing. It’s as if Sense does not show it because it’s either zero (unlikely) or negative (more likely). Another puzzle demystified.

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#10

JustinAtSense. Yes, thank you Justin I did exactly what you recommended and now I have single bubbles, and the ‘Other’ bubble is back, and larger than anything else. That simply means Sense still has some work to do, to identify other hogs.

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#11

You’re right - Other is most likely negative. Sense should probably consider an indicator in the Bubble view that that’s what is happening. Having such an indicator might help users with power accounting.
BTW - the other situation where Other might go negative is when Sense detects an on-transition/signature of a device, but misses an off-transition, leaving the bubble on, well after the device has actually turned off. Once gain, the extra bubble/on-device, can take Other int to the negative domain.

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