250W Doorbell transformer?

I’ve been puzzled by my large “Always On” load of almost 500W since I got my Sense, and yesterday I finally had a chance to investigate it circuit-by-circuit. Looks like I’ve got about 250W of hard-wired load on my circuit labeled “Basement” on the breaker panel. The only device I can think of that was still powered on in that circuit is the transformer that powers our (Nest) doorbell. Is it even possible for that thing to draw 250W continuously? Maybe due to some sort of short-circuit or design flaw?

Proving that it’s the transformer is going to be a PITA because the thing is hard-wired and then foamed to seal around the drywall.

Is there a more modern way to power my Nest? It’s not like the little bugger needs amps of 24VAC to power its WiFi.

How did you investigate Always On usage, circuit-by-circuit ? I ask, because the Always On number and bubble won’t change immediately in response to breaker switch flips.

I’m fairly certain that a Nest or Ring door bell uses 10W or less. Most often, Always On comes from an accumulation of many devices. My Always On is around 495W but I can account for all but about 50W using this methodology:

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This seems doubtful, because devices like the nest doorbell typically draw around 10-15 watts. I think that you got misleading data from your experiments. I did try to find power specs for it, with no luck, so that is a guess based on other such devices I do have data for.

Sense’s “Always On” is tricky to sort out because of the way it calculates that.

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@kevin1 yep, that’s the process I followed. You guys are right that about half of my Always On is nickel-and-dime small devices, but I have concrete evidence here that the other half isn’t a plugged-in device and isn’t many.

When i was down to just the Basement circuit on, the live meter was reading 297W solid. Flip it off, and I’m down to 22W (Internet gear on a different circuit). So something on that circuit is pulling around 250W. I totally agree the Nest itself couldn’t possibly be drawing more than 50W, but I wonder if the transformer itself could be flawed. This is a new home from a national builder that was in a bit of a rush, so I wouldn’t be surprised if they messed it up somehow.

What else could be hard-wired on that circuit that I’m not thinking of?

Good question. Other things in some basements are radon mitigation systems, pumps of various kinds (though those don’t usually run full time), blowers (some ERV’s run full time, or pretty much so), and HVAC controllers (my complex system draws about 50 watts full time all year long, for my geothermal).

That said, almost 300 watts does seem like a lot for anything I can think of.

Ah HA! There’s a 200W thermostatically controlled heater in the plumbing closet in the garage. That was the mystery load. I suspect the builder set a very conservative temperature to prevent pipes freezing, and it’s just running full-blast all winter. Thanks for your help, Andy!


Clearly, you live in a very different part of the country than we do. Builders around here even avoid putting pipes in exterior walls, and never in a place like a garage. Was -3 degrees this morning and a high of 18.

Really glad you solved your mystery. Sense is actually much like a puzzle, and solving it can be challenging…and frustrating.

Haha yeah! We live outside of Seattle, where it rarely freezes outside, much less in the garage. So now I’m wondering…that thermostat was set for well above 61°F (running constantly), and the temperature in the closet was at 61°F when I checked just now, so…how low can I take it? Is it doing anything besides keeping the pipes from freezing?

I also have about 500W of always on, and the Radon system typically draws about 80W (per the inscriptions on the unit) and is running ALL the time, not intermittently. Do not forget if you have smart plugs, smart switches, cameras, … as those could quickly make up some of the missing Watts. For example, I have the following:

16× Feit smart switches
10× Lighted GFCI outlets
14× Smart Plugs (TP-Link)
10× Night Lights

Assuming each consumes a mere 2W, the above quickly add-up to 100W. Need also to add the following if you have them:

  • Cable/Modem
  • Router
  • Network Drive
  • Stand-by power drawn by the furnace’s electronics (+ smart thermostats)
  • Wired security system DVR/NVR
  • UPS that are constantly running
  • Media Servers (Roku, Amazon Fire, Raspberry PI)
  • Smart Speakers (Amazon/Google) …
  • Microwave/dishwasher/oven/WeatherStation - they draw little, even when not running
  • Battery chargers for cordless tools in the garage
  • Aquarium pump + heater + light

When I started with Sense and saw the ~500W, I was surprised. But then, after careful inventory, it quickly adds-up.

My 0.02


Good points, and thanks for sharing.

I have an always on of 368 watts, and 167 devices in our home (actually, more than that, but some are un-plugged most of the time) at last count, only a handful have been individually detected by Sense. Some of those are devices on your list, and some not (Keurig coffee maker, for example, and the instant pot) which also draw power when turned off.

We’ve had several Keurig’s over the years, and one of them drew about 60 watts even when turned off, although our most recent one draws only 7 watts in the off mode. Another relatively big one are the TV’s which draw stand by power too. So many modern appliances draw power all the time, whether running or not.

Actually pipes near a running water heater are unlikely to freeze in any case (plenty of loss from the tank…unless it’s a tank-less of course) even in colder climates than yours, so it’s not clear what this is protecting. I’ve lived in more than a dozen places around the country, and have never seen such a rig.