Measuring idle-reduction payback

Max Heine

For the business-minded or the math-impaired, online calculators are a godsend, and there is no shortage of them when you’re considering idling-alternative equipment.

Whether you’re looking at $1,200 for a cab heater or $10,000 for a nice auxiliary power unit, you’d be a fool not to get some idea of the return on investment (ROI) period. Even if you decide against the purchase, you might be surprised by what you’ll learn about the cost of your idling habits.

Here are some of the calculators available:

ARGONNE NATIONAL LABORATORIES. This is one of the most thorough calculators, and presumably unbiased since it’s coming from the U.S. Department of Energy. For example, it addresses the cost of fuel and maintenance for any idling-reduction device. Visit Under “Research,” choose “Technology Analysis.” On the left, click “Idling,” then on right, click “Excel format.”

EPA SMARTWAY. The calculator offered by the U.S. Environmental Protection Agency’s program to encourage environmentally wise business practices has the distinction of allowing you to combine more than one idle-reduction component in the same calculation. Six technologies are listed, with default prices ranging from $900 for an automatic tire inflation system to $8,500 for an APU. Click “Basic Information” at

KOHLER. Fill in five blanks, and you get fuel savings per year and ROI for the APU. Search for “calculator” at

THERMO KING. This thorough vendor calculator shows your savings from fewer oil changes, thanks to less wear on the engine, when using the company’s Tripac APU. Visit

WEBASTO. This sophisticated calculator at breaks out idling hours to cool and to heat. Fill in a few basic fields, and the auto calculation gives you an array of idling costs and annual savings. Also, a one-click change of product revises the entire range of calculations.

ESPAR. This calculates savings over two, three, four and five years for using the company’s Airtronic D2 heater. It’s straightforward and on one page, with a note that savings from extended oil changes and prolonged engine life are not computed. Go to the “Special Programs” menu at

CARRIER TRANSICOLD. This simple one produces yearly total fuel costs saved using the Proheat Air. Go to “Performance Accessories” at

Got numbers?
Using an online calculator is a bit like figuring your income taxes: The most difficult part is getting all those numbers together.

Some default values appearing on calculators, as you might suspect, are skewed toward producing a rapid return on investment. And the same default can vary among calculators. For example, you can find the fuel cost of idling as high as 1.2 gallons per hour, and as low as 0.8 gph. If the first produces a return in two years, the second bumps it to three years – no small difference.

Before you start, determine these:

FUEL PRICE. Use today’s price or speculate on tomorrow’s. Watch for outdated default prices.

IDLE FUEL CONSUMPTION. The industry benchmark is a gallon per hour, but you should check your own rate.

IDLE HOURS. This one varies the most by operation. Figure how many idling hours will be replaced by the equipment you’re looking at, whether heating, cooling or both. Change any default that assumes you idle at the same rate 52 weeks a year.

EQUIPMENT COST. Some calculators provide a default here, but get the straight scoop, including installation costs, from the vendor.

OTHER. You won’t need these for all calculators because some don’t go into such detail; others provide their own values. But to be totally prepared, know your typical oil change cost and miles between changes, and your typical engine overhaul cost and miles between overhauls. And from the vendor, find out the rate of fuel use by the equipment and the annual maintenance cost. If those costs aren’t reflected in the calculator, crunch your own numbers to add a dose of reality to the return on investment.

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