Rough Natural Gas Estimation

Here’s an idea for a future update.

While my Sense is new and hasn’t detected them yet, I know both my gas furnace and gas water heater have electric components powered through the home.

Presuming the Sense knows when our water heater or furnace turns on, it would be really neat to pair that with the BTU rating of the appliance to get at least a rough estimate of gas usage. This is obviously presuming that these devices burn gas at a constant rate when the electricity is on, but that does fit my (entirely amateur) understanding of how these devices work.

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Hey @brian.chatagnier - at my old apartment, Sense discovered our electric igniter for our gas furnace in about 6 months. Your mileage may vary - I know it was detected once winter came around.

My natural gas-powered water heater is on an HS110, which allowed me to create the graph below. You can see it working less in summer, probably because the tank looses less heat when the basement is warm instead of cold. I know the water heater comes on several hundred times a month, so if there was going to be a native Sense detection, it would have happened by now. The electrical components inside use 108W while running, and only half of that is the powered exhaust fan, which explains why Sense doesn’t find this water heater.
Hot Water
The pump on my hydronic, gas-powered boiler was natively detected. With this and the water heater via HS110, I have enough information to do the calculation described above. My kitchen range is natural gas powered, too, but I believe its usage is negligible compared to the other two.

I’m adding my vote to this wish item!

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Correct me if I’m wrong, but I think the OP is asking for gas consumption rather than electricity consumption.

Some units especially tankless water heaters have a variable BTU based on ground water temperature, environmental air intake temperature and demand. For those devices it would be near impossible.

For fixed BTU units, like most traditional tank water heaters and also most furnaces/heat packs I could see this being possible. I have a strong feeling the Sense people will probably say that if you have a smart outlet on the device, or if it’s discovered, you could use Home Assistant etc to easily calculate the total BTU’s

I wasn’t aware there were variable BTU units out there. Good to know!

You are correct that I am looking for an estimate of how much natural gas I’m using in the app. I would be great to see a bubble for gas usage of my water heater and furnace.

I’m not aware of any other product on the market that can do this. I think it would be a great differentiator for Sense in this market. From the outside, it seems this would be a relatively easy addition to the app, as the Sense is already collecting the relevant data points.

I have to eat my words! After saying that Sense would never find my water heater, it did so this morning. The new device averages 106W while running, which is very close to the 108W measured by Kasa. The new detection came with 2 months of historic data on the native detection, so I exported that to Excel and compared it to what the HS110 had measured. The new device is picking up 3/4 of usage!


I’ll keep an eye on the new device for a while until I gain confidence in it. Then I will move the HS110 to something else. I share this so the rest of you have hope for native detection of gas-powered water heaters. Sense must be improving their algorithms behind the scenes. Thanks, guys!

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What water heater do you have? My nat has Rheem has zero electricity run to it, not even for the pilot. I take it yours is a power vent? Is that where the 106 watts is going entirely?

Yes, it is a power vent. The model is Rheem PROG40S-36N RU67 PV. There is no pilot light, as it requires electricity to run. The always on is 1W as measured by HS110, which I assume powers standby logic circuits.

Models with a power vent have a slightly higher efficiency rating since the exhaust can be cooler, as the air does not need to be hot enough to initiate convection inside the chimney. Yet because of the electricity needed to run the power vent, the costs of heating water will be higher over the power vent’s life span. These differences are small, and most people decide based on the availability of an appropriate chimney.

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So I ended up plugging everything in my utility room in a smart power strip, including my hot water heater.

My hot water heater also has a power vent. There’s an “always on” draw of 1W, and the power vent draws a full ~170W while on. I was surprised at how much electricity the gas water heater draws.

Sense ended up discovering the power vent about a week after I plugged it into the smart strip.

I would still love a bubble to show up showing my natural gas usage while it’s turned on.

I know I originally mentioned how there’s variable BTU units, but since we moved on a bit into fans, let me throw another wrench into your idea for the sake of being difficult :joy:

Most modern high efficiency water heaters reclaim the heat in the venting system and reuse it to heat the water. This is done in concentric venting systems. The fan actually stays on after the unit stops using gas in order to reclaim that heat. Additionally, most also have built in recirculating pumps which actually kick on after the gas turns off.

The reason I mention this is because it’s not so easy to tell when a water heater is using gas anymore. The water heater you have is a traditional unit, which is easy to correlate the two consumption units. This however wouldn’t be true in modern HE units.

If you have something like home Assistant installed you could easily create a custom chart that would show gas consumption based on Sense. But it would be based on your parameters.

Good to know. I had no idea these things had gotten this complex. I guess this is a trickier problem than I had assumed.

Manufacturers are getting creative due to energy regulations. It’s expensive and a water heater that once was $600 can now be over 3k for the highest efficiency, but they work well. I spend about $15-20 a year in propane to heat my hot water for the family which equates to about 5-7 gallons a year.

As promised, I kept an eye on the native detection. I now have three months of data to compare. Using hourly export, I compared native to integration. Here is the result, plotted as events per week.


If the two measurments were within 50% of each other, either over or under, I called it a Good measurement. If the native measured less than 50%, I called it a Missed On. If native was more than 50% over, I called that a Missed Off. I manually removed duplicate events caused by the device running across the top of the hour. Those duplicate events showed up in the data export as a small usage in an hour either directly before or after a larger usage. Finally, there was one case of the HS110 being offline for the afternoon and the native device picking up usage, so I called that special case Better.

Slightly more than half of measurements are Good. Unfortunately, that means that the native detection is missing nearly half the usage, so I don’t get to move my HS110 to another location. The bottom line is that this device of 108 Watts is right on the edge of what Sense can reliably distinguish. One good trend in the graph is that Missed Offs seem to have improved with time, which surprises me because of the way this physical device turns off in stages. Those stages are explained in this post:

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This would be neat to figure up using sense. I have a 2 stage heatpump / dual fuel I would like to figure out what temp to do the change over. My 3ton heatpump on stage one (70%) with the fan in the furnace running (low) is consistently at 1707watts, which I though would fluctuate a lot more. My NG furnace 75K btu is 96% afue … . Sense hasn’t found the 2nd stage of my heatpump yet. But at 100%, its 36,000 BTU… Im guessing stage one is 25K BTU / 1700 watts. Making 25K BTU for 1 hour = 1.7 kWh which cost ~24.1 cents an hour to run.

Is there a way to find how much gas roughly using with my furnace?