What is the energy of gasoline compared to the same cost of other fuels in BTUs per dollar?

Of natural gas, fuel oil, and electricity, natural gas takes the prize right now as cheapest energy source…

By Deborah Halber

First, a quick lesson in terminology: A BTU (or British thermal unit) is the amount of heat required to raise the temperature of a pint of water one degree Fahrenheit. As such it is often used to compare the energy content of different in fuels. A wooden kitchen match generates approximately one BTU — a gallon of gasoline contains about 138,500 BTUs.

MBTU (or mmBTU for a thousand BTUs) stands for 1 million BTUs — a convenient way to compare the energy content of different grades and types of fuels.

Of natural gas, fuel oil, and electricity, natural gas takes the prize right now as cheapest energy source. While the wholesale price for natural gas is around $8 mmBTU, retail is closer to $10 or $12 (and it varies a quite lot across the country), said John M. Reilly, senior lecturer at the Sloan School of Management. Fuel oil, sold right now for around $4 a gallon, generates around 138,500 BTUs per gallon. That works out to about $28.80 per mmBTU.

And electricity — at 3,412 BTUs per kwh and assuming an average price of 11 cents per kwh — comes to around $32.25 per mmBTU.

That gives electricity a bit of a bum rap, according to Reilly. While comparing fuel oil and gas is more or less apples to apples, the comparison of electricity on a BTU basis is not really fair. The heat produced by a heat pump (in which electricity is used to compress a gas that collects heat and then move it into a building), for instance, doesn’t have anything directly to do with the BTUs of electricity used. A BTU of electricity used in a heat pump can produce more than a BTU of heating. Similarly, using electricity for lighting and running motors are quite efficient ways to produce light or mechanical energy compared with gas lamps or steam engines — so even though gas is cheaper per BTU than electricity that doesn’t mean its more economical to light our homes with gas lamps.

Researchers in the School of Engineering are working on ways to increase the efficiency of conventional and alternative energy sources.

Posted: December 16, 2008

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