We have now been living in our home for over one year. Our home is completely run by electricity provided by WMECO, so this report is pretty easy.
Total energy usage from 2-10-2012 through 2-12-2013: 4197 kWh
Total cost: $701.96
Average temperature as reported by WMECO: 50 dgr F
Heating Degree Days base 63F: 5564
Notes:
2012 was a leap year.
For whatever reason WMECO is not consistent with when they bill out, causing the annual usage to be represented by 368 days.
Three occupants for the entire period.
Due to line loss, for every one watt consumed three watts need to be generated
Other data points and related anecdotes:
- For the winter, we have been happy with the heat pump set to 63 during the day and 59 at night.
- For some reason the heat pump will heat the house past what it is set to. So, assuming no solar gain, the house is usually a couple of degrees warmer than the heat pump setting–and the heat pump will come on before the temperature has fallen. The only explanation I have for this is either the heat pump infrared thermometer is reading window temperatures, or it is inaccurate. The HRV thermometer appears to be accurate.
- The house uses the first floor slab as a heat sink. During summer it keeps the home cool. Only after the heat wave, where the temperature was in the 90’s for 3 days straight, did I notice that the slab was warm.
- A couple of readings from the HRV (heat recovery ventilator) (dgrs F)
- 1/7/13 was sunny and in the low 40’s; the indoor temperature rose to 71. The night was in the upper teens, the heat was off, and we only dropped to 64 by 7:00am
- 1/3/13 Overnight was in the lower single digits, the heat pump was set to 63 and the indoor temperature was 62.
- The average humidity in the home so far this winter is around 40%
For comparison:
“In 2010, the average annual electricity consumption for a U.S. residential utility customer was 11,496 kWh […]. Tennessee had the highest annual consumption at 16,716 kWh and Maine the lowest at 6,252 kWh.” Source: http://www.eia.gov
Only 26% of US homes use electricity for heat. Source: http://visualeconomics.creditloan.com
My goal for next year is to be able to break down the usage into heating, cooling, cooking, refrigeration, ventilation, and hot water. This will require the installation of kilowatt meters by an electrician. The plug-in kind can only monitor the refrigeration and ventilation.
Design & Construction of Spartan & Hannah's Home 
Did the minisplit systems perform well this winter? My wife and I are looking at the new H2i technology from Mitsubishi, “effective” to -13F. We would need to do an energy retrofit on an older home to make it work though. I was wondering if you had to kick in any additional heating over the coldest winter days this year?
Hi Allan, The minisplit performed fantastically for us this winter. We used no additional mechanical heat source. Don’t forget though, we do benefit greatly from passive solar heat gain. The wonderful thing about passive solar is that it gives when you need it most: the coldest days are most often are sunny and crystal clear. Cloud cover tends to trap heat from the earth, much like insulation. Don’t forget to consider your local heating degree day analysis. If our home was in northern Canada our one 12,000kbtu heat pump wouldn’t cut it.