I owe my children and my as-yet unborn grandchildren and great-grandchildren a big fat apology. You see, I just put them on the hook for the new car I bought this weekend.

Allow me to explain.

Until last week, I was driving a 1999 Chrysler minivan with approximately 127,000 miles on it. The last time a mechanic looked at it, he told me it needed at least $3,000 worth of engine work, without which its days were limited. I decided to take my chances and just stay off the interstates. I didn’t want to be known all over the AM radio dial as the stall or engine fire on the top end of the Perimeter, backing up traffic all the way to Spaghetti Junction or the Cobb Cloverleaf.

Then we heard about the federal governments CARS—or “Cash for Clunkers” program. And lo and behold, my van qualified—barely—since it was rated by the EPA at 18 miles per gallon. To make a long story short, with dealer incentives and a generous government grant, I’m now driving what my wife calls a “mobile soda can.” And the old van—so full of memories, as when my son, then a toddler, threw up all over the brand new car on our way to Chicago, or when my daughter, then a toddler, shrieked all the way from Hilton Head to Beaufort—is on its way to the junk heap.

Was it worth it? To me, yes. I have reliable basic transportation at almost 50% off the sticker price. (And XM radio free for three months… just long enough to get addicted!)

But to the taxpayers, I’m not so sure. Let’s look at the numbers.

First, there’s the cost—$1 billion, to be precise. The CARS vouchers are for either $3,500 or $4,500. Let’s simplify and make the average voucher $4,000. Your children, grandchildren, and great-grandchildren will subsidize the purchase of—give or take—250,000 cars this year. Let’s assume that half those cars wouldn’t have been purchased without the subsidy. In 2007, slightly over 16 million light vehicles were sold in the U.S. I know numbers have declined since then, but we’re still talking about a bump of less than 2% (and probably more like 1%) in sales, thanks to those future taxpayers. That’s not a whole lot of stimulus bang for the buck.

But perhaps the program can be defended in terms of energy independence and carbon dioxide emissions. If my case is anything close to the norm, I’m not so sure.

The program, of course, is intended to replace less efficient with more efficient cars. The EPA tells me that my old van consumed 19 barrels of oil a year and that my new car consumes 11.8. Generously rounding up, that’s a savings of 8 barrels of oil a year. Multiplied by 250,000, that amounts to the non-negligible sum of 2 million barrels a year. The U.S Energy Information Administration tells me that U.S petroleum consumption is roughly 19.5 million barrels a day. So, taking my case as the norm (I know it isn’t, but humor me), the CARS program might save us about 10% of one day’s petroleum consumption. That’s less than 3 hours of fuel, or about 0.02% of our annual petroleum consumption. For a billion dollars. You can think of it another way, if you want: it’s about 40% of one day’s domestic production or 20% of one day’s imports. A billion dollars is real money, but, to my mind, we’re still pretty far from talking about real energy savings.

And then there are the greenhouse gases. The EPA tells me that my old van emitted about 10.2 tons of carbon dioxide a year (roughly comparable to what I emit when pontificating from the podium, I suspect). My new car emits 6.3 tons. That’s a savings of roughly 4 tons a year. Multiplied by 250,000, that’s a million tons of carbon dioxide less. Not bad.

According to the Energy Information Administration, in 2006 the U.S emitted approximately 5.9 billion metric tons of CO2. The CARS program reduces our annual emissions by less than 0.02%. For a billion dollars.

So there you have it. Not much stimulus, not much energy independence, and not much reduction in greenhouse gas emissions, all for only a billion dollars.

I like my new car, but I’m going to have a heck of a time explaining to my children, grandchildren, and great-grandchildren how I paid for it.

Joseph M. Knippenberg is an adjunct fellow of the Ashbrook Center. He is Professor of Politics at Oglethorpe University.