Author Topic: Heat Pump energy use  (Read 488 times)

wjquigs

  • 5 O'Clock Shadow
  • *
  • Posts: 18
Heat Pump energy use
« on: January 11, 2022, 06:34:02 PM »
Hello Mustachians,
This past summer I installed a Mr Cool heat pump in my attic in Seattle. While I didn't get it done in time for the heat wave, it's been heating my second floor well since fall.
When I read about Mr Money's experience doing the same, and that he'd put in an Emporia energy monitor, I knew I had to get on that bus. Mine arrived a few days ago and I got it set up today. Emporia support chat was excellent, BTW. They had great advice for fixing what seemed weird.
Wondering if others see similar consumption to mine. The outside unit (inverter) seems to run at 3-4kw, while the inside unit runs at around 150 watts for 24k BTU. This seems within expectations. The first floor of my house has a high-efficiency natural gas heater, which draws around 300 watts for 60k BTU (obviously this is just the fan).
Previously the upstairs was heated with Cadet wall heaters, so now I'm using less electricity to keep the whole upstairs warm instead of basically running a hair dryer in each room.
William

uniwelder

  • Pencil Stache
  • ****
  • Posts: 931
  • Age: 42
  • Location: Appalachian Virginia
Re: Heat Pump energy use
« Reply #1 on: January 17, 2022, 05:17:51 PM »
Comparisons are impossible based on the numbers you're giving--- size of house, quality of insulation, area of country, inside and outside temperature, etc.  Your 24,000 but/hr mini-split was running at about half capacity for the time the compressor is operating from what I understand--- 3.5 kw is equal to 12,000 but/hr.  I have no idea how often its cycling on/off.  If its running 20 minutes out of 60 at half capacity, you're operating 1/6 capacity overall.  Hopefully you've been having mild winter weather, so when you really need it to be putting out heat, you have the proper amount of capacity, without it being oversized too much.

150 watts energy use of the inside unit makes sense--- its just a small blower and some electronics.

I don't have an Emporia energy monitor, but have been thinking about getting one.  I've had to replace my well pump twice in the last 4 months, and being able to track energy use could be a great diagnostic tool for such things.

I really like mini-splits.  Previously had a 1.5 ton Mitsubishi in our 750 sq ft house, 2 ton LG in our current house, and just recently put in a 3 ton LG air handler unit in a new rental.  In our house, we've been able to run it all summer long without guilt.  It doesn't get very hot here, but is quite humid, and running it in dehumidify mode keeps it very comfortable.  Cost is about $10-15 per month (100 kWh) extra electricity, which is well worth it to prevent mold and feel nice.  Great in the winter too.  As the primary heat source, it uses 400-700 kWh per month in our 1,700 sq ft ranch in Appalachian Virginia.  Previous house used about 300-400 kWh per month through the winter.