Today I turned off the heat pump. Not permanently, but it doesn’t look like it will get much use this week, and the prospects for significant electricity use from here on out are slim, both because the weather is getting warmer, and because the heat pump efficiency goes up as outdoor temperatures increase.
So far this winter we have used 2,005 Kwh (about $310) to run the heat pump and 632 Kwh ($98) for hot water. We also burned 1.2 cords of wood and 71 gallons of oil. The total cost at today’s prices is $839. By comparison, last year we burned 491 gallons of oil and about 1.6 cords of wood. At today’s prices that’s about $2,000.
Here’s our oil use over the past five years:
Here’s our total heating energy consumption over the past five years:
You can see that we used around 100 million Btus pretty consistently over the first four years. Our house is about 3,000 sq ft so that works out to about 33 thousand(K) Btu per square foot. So you may be wondering how we got through the winter with 55% less heat. The answer is that we transferred that heat from the outside air to inside the house, much the same way your refrigerator removes heat from the freezer and blows it into your kitchen.
It was a very mild winter and maybe we used 10%-15% less energy. So we may have only cut our heating bill in half. Not too bad. With another heat pump, we could just about eliminate the use of oil and wood completely. I think it would be cost competitive with store-bought wood and certainly a whole lot easier.
A key attribute of these changes is that comfort has increased. We used to keep it at about 68 with oil only. When we started burning wood, the big room became very comfortable because it was always 70-71 and of course real toasty sitting near the stove. This year, the central part of the house has been 70 most of the time as well.
I didn’t mention that the oil use in past years included hot water, which we have switched to solar with electric backup. Over the past 7 months we have used 632 Kwh ($98) for HW. The sun has provided about half of the energy during that period. Over the remaining 5 months I expect the solar percentage to average 90% or more. Ill post details of that system another day.