Energy Selector Slide Rule

The Energy Selector slide rule is a convenient tool for making "apples-to-apples" comparisons of various heating fuels on the basis of cost per BTU.
Energy Selector Slide Rule - Articles


The Energy Selector contains the data for the following eight fuels:

  • #2 Fuel oil (heating oil)
  • Propane
  • Natural gas
  • Electricity
  • Coal
  • Shelled corn
  • Wood pellets
  • Firewood

Using the Energy Selector

To find the equivalent costs of these eight fuels for the same BTU heating value, simply align the slide to the current price for one of the fuels and then read straight across (on both sides).

For example, if the quoted price for #2 fuel oil (often simply referred to as heating oil) is $4.50 per gallon, move the slide so that the arrows point to $4.50 for fuel oil. Then read straight across for equivalent prices of $3.15 per gallon for propane, $3.40 per therm for natural gas, and 13.75 cents per kWh for electricity.

On the other side of the Energy Selector, read equivalent prices of $790 per ton for coal, $10.50 per 50 pounds for shelled corn, $530 per ton for wood pellets, and $580 per cord for firewood.

The equivalent prices of the various fuels have the same cost per BTU. If any fuel can be purchased for less than its equivalent price, a savings is involved.

For example, when the price of propane is $3.30 per gallon, then the equivalent price for electricity is 14.25 cents per kWh. If electricity can be purchased for less than its equivalent price when propane is $3.30 per gallon, then using electric resistance heat will yield a savings compared to propane.

Continuing with this example, if the price of electricity is 9.5 cents per kWh, then the most that you should pay for propane to get the equivalent amount of heat is $2.20 per gallon.

The price for natural gas is listed on the Energy Selector as dollars per therm. One therm is the same as 100,000 BTU. One dekatherm, which is 1,000,000 BTUs, is equal to 10 therms. Since one cubic foot of natural gas is equal to approximately 1,000 BTUs (within 2-3 percent), then one therm of natural gas is approximately equal to 100 cubic feet. Likewise, one dekatherm of natural gas is approximately equal to 1,000 cubic feet.

Shelled corn is usually sold in either 40- or 50-pound bags for consumer use in corn-burning stoves and furnaces. While corn is priced on the commodity markets based on dollars per bushel, it is usually sold to consumers in terms of either dollars per 40- or 50-pound bag or dollars per ton.

An effective strategy for coping with the high costs of energy is to establish dual- or triple-fuel flexibility so that you can switch easily from one fuel to another.

Energy Selector tool

The energy selector  can be purchased online for $1.30 plus shipping.