... Worked perfectly. We had a high of 19F yesterday and a low of -10F (technically, -9.6F) overnight.
It's nice and toasty inside, and yes, we left all the settings where we always leave them, meaning that we did a slight setback in the setpoint temp at 9 PM (temp goes down to 64-65 with a setpoint of 62) because we like it cooler for sleeping, and then an increase in setpoint temp at 6 AM (setpoint of 65 keeps indoors at about 68). In fact, the setpoints being off by about 3F is the only annoying thing about these Mitsubishis (this one is a 12K).
The mini-split did use electricity from midnight to 6AM, and yes, it used more to get the temperature back up. How much more? See the graph below. That spike will come back down in the next hour or so, and given that it's spiking to only 367 WH, that's a very manageable spike (update: down to just 234 watts at 7:30 per the live data from the Emporia Vue). As shown, the peak 15-minute demand in the past month has been only 538 watts, and we've used just over 3 KWH for the past 24 hours. Our peak 24-hour use in the past month has been 4.127 KWH (that's a period with three decimal places). I think my wife had the deck door open as she fiddled with some holiday lights. If we were on grid, that's about 95 cents US for 24 hours, to heat 910 SF of living space (plus two long knee wall areas of storage), in Maine, in late Dec and January.
My point here isn't to brag, although I am proud of the building's performance given that I designed it. Rather, my point is that in a building designed for energy conservation, an air-air heat pump designed for the temperature/climate where it is installed can perform very well in a very cold climate. And with a bit more use of electricity, they can heat a building with somewhat less insulation and air sealing. Those who say heat pumps can't perform well in a cold climate are simply using a heat pump not designed for the cold. When I see words like "heat strip" I think, "Not a cold climate unit." Some will likely chime in with arguments. Have at it. This is real-world data, written in a warm and toasty room at below 0F outside temps, in a totally off grid building. Just insulate and air seal, and buy the right unit for your local climate. They're not cheap, but this is how they perform.
It's nice and toasty inside, and yes, we left all the settings where we always leave them, meaning that we did a slight setback in the setpoint temp at 9 PM (temp goes down to 64-65 with a setpoint of 62) because we like it cooler for sleeping, and then an increase in setpoint temp at 6 AM (setpoint of 65 keeps indoors at about 68). In fact, the setpoints being off by about 3F is the only annoying thing about these Mitsubishis (this one is a 12K).
The mini-split did use electricity from midnight to 6AM, and yes, it used more to get the temperature back up. How much more? See the graph below. That spike will come back down in the next hour or so, and given that it's spiking to only 367 WH, that's a very manageable spike (update: down to just 234 watts at 7:30 per the live data from the Emporia Vue). As shown, the peak 15-minute demand in the past month has been only 538 watts, and we've used just over 3 KWH for the past 24 hours. Our peak 24-hour use in the past month has been 4.127 KWH (that's a period with three decimal places). I think my wife had the deck door open as she fiddled with some holiday lights. If we were on grid, that's about 95 cents US for 24 hours, to heat 910 SF of living space (plus two long knee wall areas of storage), in Maine, in late Dec and January.
My point here isn't to brag, although I am proud of the building's performance given that I designed it. Rather, my point is that in a building designed for energy conservation, an air-air heat pump designed for the temperature/climate where it is installed can perform very well in a very cold climate. And with a bit more use of electricity, they can heat a building with somewhat less insulation and air sealing. Those who say heat pumps can't perform well in a cold climate are simply using a heat pump not designed for the cold. When I see words like "heat strip" I think, "Not a cold climate unit." Some will likely chime in with arguments. Have at it. This is real-world data, written in a warm and toasty room at below 0F outside temps, in a totally off grid building. Just insulate and air seal, and buy the right unit for your local climate. They're not cheap, but this is how they perform.
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