Sunday, June 28, 2015

One family's energy budget

Anne and I have been trying to live more sustainably for some years. We have a ground-source heat pump for heating and cooling which uses much less energy than our high-efficiency gas furnace, even if you count the inefficiency of power plants and transmission infrastructure. We also have a modern wood-burning stove in my office, so some of the "heat" comes from making firewood, especially since all the wood must be hauled uphill. We have some gasoline-powered tools, like a chain saw and lawn mower, but we are far behind our neighbors in that department.

We have almost entirely switched over to LED lighting. We have about 10 kW of solar panels installed. We grow quite a bit of our own food. We drive Diesel cars. So how well are we doing, really? Is it enough?


Here's a rough breakdown of our annual energy budget:

13 MWh of electricity, of which 4.5 MWh is heating and hot water.
2 MWh of gas, for supplemental heat in the coldest weather.
14 MWh of Diesel fuel for our cars.
11.3 MWh for air travel, one round trip to Europe (MSP-AMS).
0.2 MWh gasoline, for all the power tools.

That's about 40 MWh annually, or about 2.31 kW/person for the whole year. In addition, there's
-14 MWh of solar production.

That gets us down to 26 MWh annually, which is about what we consume for transportation. It's also about 1.51 kW/person, or about 2 horsepower per person continuously. If we had to do it with actual horses, how many would we need, and how much land to grow fodder?

Eliminating the air travel and switching to electric vehicles would cut out roughly 20 MWh, bringing our net to roughly 350 Watts/person, under 1 hp for the two of us. We could probably cut out another MWh/year by tightening up the house and replacing some of the older windows, but what's the rest of the electricity used for? Cooking, dishwashing, laundry, computers, television, and the rest of daily life. Moving to a condo in the city might save a fair amount, but we like it here.