How's Your Unit?

April 23, 2008 – 2:00 am

Even though it snowed less than a week ago here in Seattle ("I'm dreaming of a white... Passover?"), we're barely a month away from Memorial Day weekend, the official kick off of Summer. To me, Summer means two things: barbecues and air conditioners. And the cool/hot thing is that they're both rated with a similar unit of energy.

The humble BTU, or British Thermal Unit is another of those holdovers from the imperial system of measurement that refuses to give way to the metric system: the BTU is the amount of energy needed to raise the temperature of one pound of water by one degree Fahrenheit.

Gas grills and air conditioning units are both rated in BTUs, grills by how many BTUs they can add to the environment and air conditioners by how many BTUs they can remove from it.

For example, this portable gas grill has an output of 8,500 BTUs per hour. That's roughly equal to this portable air conditioner. Technically, you could light the grill, crank up the AC, put them both in a room together, and achieve some sort of thermal balance.

But the cool thing is that BTUs per hour can also be converted into horsepower. According to Wikipedia, one horsepower is approximately 2,544 BTU per hour. So that little gas grill has 3.34 horsepower. Put, put, put, put.

Another put-put would be the new Smart car that's coming to America.

These gas-sipping little two-seaters deliver 33 miles per gallon city, and 41 miles per gallon highway on a 70 horsepower inline three. Still, while this put-put-puppy only puts out 21.54% the horsepower you'd get from a Porsche 911 Carrera (the cheap one, MSRP $73,500), it would blow the doors off an $9540 top of the line Viking gas grill, which puts out the heat equivalent of around 47.17 horsepower, or 14.51% of the Porsche's horsepower.

But how would the horses play out in a dollar for dollar comparison?

• Porsche - 325 horsepower - $73,500 MSRP - $226.15 per horsepower
• Viking VGIQ530-4RT grill - 47.17 horsepower (120,000 BTUs per hour) - $9,540 MSRP - $202.25 per horsepower
• Smart ForTwo "Pure" Coupe - 70 horsepower - $11,590 MSRP - $165.57 per horsepower

So come barbecue season, if you've got a new 50,000 BTU grill, you can gloat that it blows the doors off your neighbor's new 15.5 horsepower riding mower. But whatever you do, don't try to ride the barbecue. It hurts. Don't ask how I know.

On Friday, we'll be calculating how many Twinkie snack cakes it would take do 0-60 in under 6 seconds.