I was pondering my recent electric bill again, still trying to think what electrical appliances I could possibly be using less when the house is cold. Then I realized that the most obvious one of all had escaped my attention: the furnace.
The furnace burns oil, but the oil burner and pump run on electricity. The contraption makes a considerable whooshing racket when it’s running, so it occurred to me that it might use a non-trivial amount of electricity. I went down cellar to read the labels.
And it’s true. The various electrical parts of the oil furnace together draw 7.5 amps, or 900 watts. The burner says it will burn 1.05 gallons of oil per hour, if running non-stop. Some quick math reveals that for every 100 kWh of heat the furnace extracts from oil, it also uses 2.7 kWh of electric. In other words, the oil furnace is roughly 2.5% electric. Of course, that electricity does get turned into heat, too, but most of it stays in the cellar where I don’t really want it anyway.
In dollars and cents, it’s also non-trivial. If we burn 100 gallons of oil in a month (which I quite easily did, midwinter, in the old days) that requires 86 kWh of electricity, which adds about $13 to the month’s electric bill. It’s about equivalent to 15 loads of laundry in the electric dryer. I think this clears up some of the mystery of why my bill last month was less than I expected.