Energy sources are purchased in unique units: wood by the cord, coal by the ton, etc. Yet all can be stated in equivalent energy units. For example: a gallon of fuel oil is the energy equivalent of 40 kilowatt-hours of electric energy. The rate of energy use (in all forms) worldwide is 15 trillion watts. On the average, each of the 6 billion people on Earth use energy at the rate of 2.5 kilowatts. In the U.S. energy is consumed at a rate four times greater. A kilowatt is the energy of one large electric stove-top unit on “high.” If we focus on just petroleum use per Maine resident (33 barrels per year), the rate of energy use is about six kilowatts. If we include other energy use in Maine – natural gas and hydroelectric – the per-person rate of energy use is about 10 kilowatts. Twenty-four hours per day, 365 days per year, each of us in Maine, all 1.3 million of us, is consuming, on the average, the energy equivalent of a very large electric stove with all burners, broiler and oven on “high.”

Richard Hill is a retired emeritus professor of engineering at the University of Maine.