With winter finally setting in, and being the first year in our new house I would like to put some sort of measurement on how often the furnace is working, before I get the bill. Are there any known methods of measuring how much fuel furnace is consuming, other than monitoring the gas meter outside the house? What is the best way?

  • What exactly do you mean by "how hard"? They are not humans - they are either on or off, for the most part. Are you asking about efficiency? – Steven Jan 12 '12 at 20:18
  • I have a programmable thermostat, and the temperature changes dramatically from day to night. Looking for insight into methods/tools to use to monitor the furnace and when its on. – Styler Jan 12 '12 at 20:30

Some of the more advanced thermostats will track how often they are running. I have a Filtrete Wifi-Enabled Progammable Thermostat. It gives you a per-day total of how often the heat and A/C are run. You can also download an hour-by-hour export of the usage in CSV format.

I am in no way affiliated with this company. It is simply a product I have installed at home

It also gives you an idea, for a given temperature change, what the % change in heating cost will be:

Web Portal

  • I really like this, and I'm debating just buying one given the price is right.. for now I might just take meter readings until I see other options as well. +1 nice tool – Styler Jan 12 '12 at 21:08
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    I love this thing! There is an android app, iphone app, ipad app, cloud management.. and for $100, how can you go wrong?! the only thing you need to verify is that you have a wire at your thermostat connected to your furnaces C terminal. If you do not you either need to run an new wire or use a transformer to power the thermostat. – Steven Jan 12 '12 at 21:10
  • Question, does this model have inputs for a humidifier as well? We have an old Aprilaire attached to our furnace with a control unit right next to our current humidifier. – Styler Jan 12 '12 at 21:10
  • It does not but the CT80 model does: radiothermostat.com/control.html – Steven Jan 12 '12 at 21:11
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    There is also a JSON API that you can use to get the runtime for the current and prior day directly from the thermostat if you like to write code. Here's the beginning of the current output from mine: {"today":{"heat_runtime":{"hour":1,"minute":1}, – TomG Jan 13 '12 at 0:21

Most furnaces have an AC component that is powered on when it is running. Put a ac clock in parallel with this. For up to 12 hr this will tell you the time the device is running. Other types of timers will go for longer. Most furnaces run at two speeds stop and full.

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