How to track the cost to use a natural gas appliance

I’m building a new home and plan to put radiant heat in the basement and garage floors. I’ll use a natural gas powered boiler to heat the water for the system. Does anyone know of a sensor that I can use to track the cost to run this boiler? I assume the sensor would need to monitor the natural gas use in order to tell me this, correct? Does such a sensor exist?

Or, could I use a water flow meter on the heated water pipes to somehow calculate it? Maybe tracking the flow rate plus the delta of the supply and return water temp? If I can do it that way I’d prefer to because I could break it up by zone.

The safest and most accurate way to do this would be with an ultrasonic flow meter on the gas line. However… they aren’t cheap

There are many types of flow meters you can use but I don’t think you will find anything that I would consider ‘affordable’. This is due to them having to be rated for use with a flammable gas (Ex rated). Odd’s are that ultrasonic will be the cheapest.

Note for the above: Not sure where you are in the world but be aware that the inferior ATEX standard used in the USA is not legally accepted pretty much anywhere else in the world. The ATEX standard allows manufactures to ‘self certify’ rather than using a third party. Australia for example only allows equpment certified with AusEx or IECEx.

Depends upon the type of meter. Some have rf modules that broadcast every x seconds. Those can usually be captured with rtlamr. From there, you can pipe the data into home assistant. I use for getting water usage into HA. Others wait for a wake-up signal before broadcasting so there require a physical device attached to the meter. Others are just mechanical dials, etc, etc. Mine is mechanical with an add-on transmitter that only broadcasts when it receives the wake-up call, thus, I would need to read using sensor attached to the meter.

I ended up writing some python code that I ran from an esp8266 running micropython. It had a sensor that attacked to the quicker moving dial so I could get more detailed measurements. The sensor detected the color change of the dial. Esphome can now easily do this using the pulse counter. The problem was, ambient sunlight would cause there to be no measurements from 11 AM until 4 PM. Aside from completely covering the sensor and meter, I had no way around this other than to install my own sensing device inside. I opted to just remove the device and no longer monitor gas.

Your other option is an addon ultrasonic device like mentioned above.

I’m guessing you are referring to the main meter supplying the house…? Brad is asking about monitoring a specific appliance.

You are correct. There’s nothing affordable to do such a thing for gas. Smappee has an addon gas module but the cost is still high. You can get gas meters with pulse outputs on ebay but they’ll set you back $120+ Monitoring the main meter and comparing to previous years is the only affordable way I know of.

Monitoring water usage might be the cheapest way to do it. From there, you can deduce gas consumption. You can get water meters with wired pulse outputs on ebay for under $50.

Is this a variable firing rate boiler - or does it just have an on/off setting ?

If it is an on/off then there is no need to monitor the gas flow - you will know what it is rated to use, you can run an empirical experiment to monitor it over an hour at the meter and confirn it is using what is should.

From there it should be easy to deduce when it is running - monitor current flow on the circulating pump for instance, monitor input and output temps on the heating lines from the unit to confirm it is running etc

If you call for heat for 2 hours a day you can then do the maths to work out what it has cost you.

I do something similar with our boiler - it is a single speed single firing unit - so i control it through a relay to actually switch it on when i want and then note those times down - from there i can calculate the approx running cost each day.


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