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Measured Electric Usage - Quadrafire Mt Vernon AE. Less than I thought!

Post in 'The Pellet Mill - Pellet and Multifuel Stoves' started by mcmanus, Nov 11, 2008.

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  1. mcmanus

    mcmanus New Member

    Joined:
    Jun 5, 2008
    Messages:
    28
    Loc:
    Midcoast Maine
    Back in September I suggested to another forum member that they could measure the electrical usage of their pellet stove with a Kill A Watt meter.

    At the time my stove was not yet installed so I couldn't do so myself. It came in very soon after and I have been using it very happily for the last 6 weeks or so. It was time to do that measurement.

    [​IMG]

    I've got the Mt Vernon AE, which is a beast in many ways. It is has a high BTU rating of 60K, it has that auto-clean cycle it does every so often, and of course a built in ignitor. I think we're all especially interested in how much energy that ignitor uses.

    Here is what happened, when I plugged it in set to 'off'. (T is elapsed time, in minutes):

    T=0: Auto Clean session that happens at every startup draws 15 watts
    T=2: clean finishes, a fan runs. Uses 13 watts.
    T=3: fan shuts down. Stove is idle. Still draws 8 watts to the electronics.
    T=4: I turn it onto Medium-Low, the ignitor goes on. This draws 382 watts (3.2 amps)
    T=14: The ignitor goes off. Draw is reduced to 25 watts and ramps up to 34 in a minute or two and then holds steady.
    T=28: I turn it up to High. The load goes up to 47 watts and holds steady there.
    T=40: I'm sweating too much and turn it back to low.

    All of the stages were fairly stable regarding how much energy they used within the stage. The ignitor stage was very stable, the run stages varied about 20% as fans picked up and slowed down. I used their top values to get a worst case scenario.

    I only include the Amp rating on the ignitor as useful for figuring out what circuit to plug the stove into and not pop a breaker - a 3+ amp load for the ignitor could certainly put a heavily loaded circuit over the top. Normal running conditions only use a fraction of an amp.

    The first thing that strikes me is how long that ignitor stayed on - 10 minutes. The fire started after maybe 2 or 3. But even at 10 minutes, the energy it uses is really very reasonable. 10 minutes at 382 watts is .063 KWH

    My cost of electricty right now in mid coast maine is $0.153 per KWH. That means lighting a fire, comprised of an ignitor session and an auto clean, uses .064KWH which in turn costs a little less than a penny ($.009) in electricity. That's good news!

    Assuming the stove runs 18 hours a day (typical for me) it probably goes through a clean cycle every 4 hours.. let's call that 5 cycles a day and round up to a nickel in total startup costs.

    Running the fans and auger on med-low for 18 hrs would use .612KWH of energy, or a little over 9 cents worth at my rate.

    Add the two together and we're looking at 15 cents a day ($4.50 a month) even when rounding everything up and ignoring the fact that I'm double counting the ignition periods as ignitor + burn time.

    Worst case with the stove set at high it would use .846KWH over the 18 hours (exclusive of startup costs). At my rate that's about 13 cents. Include the starting costs and, even running the sucker on high, you're looking at 19 cents a day or about $5.70 a month. Pellet costs runinng this beast on high all the time are another thing all together ;)

    I really expected it to be more than this. I am interested in comparing it to the savings of not running the circulation pumps on my FHW oil furnace.

    Final fun fact: leaving it plugged in, but off, for the 8 warmer months of the year costs about $7 at my electric rate. The cost of doing nothing in this age.

    Hope this is useful to other folks.

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  2. eric_s

    eric_s Member

    Joined:
    Jul 22, 2008
    Messages:
    87
    Loc:
    Rhode Island
    Thanks for the info. I have the same stove and was told by the dealer it draws very little power relative to a lot of other stoves. Never would have thought it was that low. When you ran it on high, did you give it long enough for the convection fan to really start blowing?
  3. mcmanus

    mcmanus New Member

    Joined:
    Jun 5, 2008
    Messages:
    28
    Loc:
    Midcoast Maine
    I think so - it was cranking as much as I've seen it.

    The stove does have "quiet" and "normal" settings which I had forgotten about when I made the original post. This was all on quiet, which is probably a little less power than normal. (oddly, I believe the default is quiet which really makes you wonder what the meaning of normal is :))

    I'll leave the meter on for a few days and check back on the aggregate usage then. It won't give the fun breakdown between stages, but it ought to be enough to see if 1KWH/day is in the ballpark. My guess based on the trial, is it is actually significantly high. That would be really impressive.

    The next week is supposed to be in the 30's and 40's here. (28 tonight). So that's a decent test, but obviously it will run harder in January.
  4. eric_s

    eric_s Member

    Joined:
    Jul 22, 2008
    Messages:
    87
    Loc:
    Rhode Island
    Yea...I missed the 12 minutes of operating on high in your original post. Mine usually ramps up the fan quicker than that.
    Please keep us posted.

    As for the fan, I noticed when I got the unit that the fan was set to quiet. I switched it to normal on day one and have not changed it since. Figure the more air movement through the heat exchanger the better. Plus I really don't find "normal" to be loud.
  5. mcmanus

    mcmanus New Member

    Joined:
    Jun 5, 2008
    Messages:
    28
    Loc:
    Midcoast Maine
    48 hours after starting the meter the total usage is 2.01KWH. So 1KWH per day.

    The two days have been similar. Highs of about 45, lows of about 25. Mostly cloudy. Stove runs on auto shifiting between low, medium low, and medium as needed except when bringing the house up to temp in the morning as it is setback to effectively off for 6 hours overnight. Used about 80 lbs of pellets over that interval.

    For some reason when I talk to folks about the stove they fixate on "but you have to plug it in" as a big detractor. hopefully that shows with, at least this stove, that is not a significant factor in terms of energy consumption. Its true that it isn't a great emergency heat source, but we bought it to supplement the furnace not to make the house disaster proof. I've got a small generator to hedge against that.
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