With fluctuating energy costs, you need to evaluate which energy source gives you the best value for the money, notes Dennis Buffington, Penn State University agricultural engineer. But you can’t make that decision based on price alone.

For example, if propane sells for $2.50 per gallon and No. 2 fuel oil sells for $2.80 per gallon, don’t assume that propane is cheaper just because the cost is 30 cents less per gallon. The only way to determine which fuel is cheaper is to compare the cost on the basis of dollars per million BTUs (British thermal units).

An online calculator can help you compare the cost of many traditional and non-traditional fuels on this basis. The Energy Cost Calculator is at: http://Energy.cas.psu.edu