Apples, Oranges, and BTU's
We can't compare a kilowatt-hour of electricity to a gallon of fuel oil unless we convert the energy content to common units. We use the British Thermal Unit (BTU) to compare energy sources. One BTU is a very small amount of energy...about what you get from burning one wooden kitchen match. We measure UNH energy quantities in terms of millions of BTU's (mmbtu).
To be fair, we have to adjust energy sources for "end use
efficiency." For example, almost all of the electric energy used to power an
electric heater actually goes toward warming the room. On the other hand, when we
burn oil some of the energy goes up the chimney and more energy is lost as the hot water
travels through the pipes to the radiator. The figures used in this section were
adjusted for end use efficiency by the following factors:
Electricity: 95% efficiency Natural gas:
70% efficiency Number 6 oil: 70%
efficiency Number 2 oil: 80% efficiency
Propane: 85% efficiency
BTU content for electricity is based on energy content at the UNH connection to the transmission line (3410 btu's per killowatt-hour). Much more energy is used to produce that electricity at the utility company generating station. About 70 percent of the "primary" energy (fuel oil, natural gas, uranium concentrate, coal, etc.) consumed at the generating plant is lost to waste heat during the generation and distribution process.
Here's the picture when we convert out energy sources to
common units and relative efficiency.
