Before you buy that air conditioner

So, it’s summer. It’s hot and it’s going to get hotter. You may be thinking of buying an air conditioner.

Before you do, though, why not buy new lightbulbs–those swirly compact fluorescents–instead?

Sure, you answer. Or hey, why not a new camera lens? Or a hundred pounds of bacon? Or a pony?

Bear with me. This actually makes sense.

If you’ve ever considered replacing your incandescent lightbulbs with CFLs, your thought process probably went something like this: “CFLs are more expensive, but they save on electricity and they last longer. Is the up-front cost worth the long-term savings?”

Whether your answer was yes or no, though, that was the wrong way to think about it.

See, a 60-watt incandescent lightbulb that puts out no more light than a 15-watt compact fluorescent isn’t just costing you 45 watts. That wasted energy becomes heat. Heat that goes into your home. Heat that you then take out with an air conditioner.

Now: According to this, those 45 watts will add 153 British thermal units (BTU) of heat in an hour. Conveniently, air conditioners are rated in BTU per hour. So let’s say you change five bulbs. That’s around 750 BTU that you don’t have to remove.

And remember, ACs don’t usually run continuously; a 6,000 BTU unit that runs a third of the time is only removing 2,000 BTUs per hour.

So if you switch your bulbs, you may find that you can get a smaller (and cheaper) air conditioner. You may not even need one at all.

And if the savings on the air conditioner is more than the cost of the bulbs, there’s no up-front cost at all. Going green means savings now *and* lower electric bills (much lower, thanks to the lower AC costs) later.

Note that the waste heat isn’t an argument for using incandescents in the winter; they’re not efficient heaters.

Now: This all depends on a million factors: when you light your home, where your bulbs are, how insulated your home is, and so on. But electrical bulbs certainly can make a difference. I know because they did for me; I got an air conditioner a decade or so ago, used it for two summers, and then stopped even bothering to take it out of the closet. Eventually I gave it away. I never understood why I’d stopped using it–the summers were no cooler, and I was no more tolerant of heat–until I remembered that that was when I’d switched to compact fluorescents.

So before you buy an air conditioner, switch your bulbs. You may save on both ends.

By the way: this phenomenon, where taking a larger view gets us out of the mindset of tradeoffs between up-front costs and long-term savings, is actually pretty common when you’re dealing with environmental issues. Lovins, Lovins, and Hawken’s Natural Capitalism is full of examples. For instance, if you’re building an office building and deciding whether to pay extra for well-insulated windows, that’s a tradeoff if you just compare the cost of the windows to your future heating and cooling bills. But less heating and cooling means that you can install smaller equipment and smaller ductwork, thus making a smaller building overall with the same useable floor space (and the smaller building means even less heating and cooling). If you save more making a smaller building than you spend on the windows, there’s no tradeoff.

So why don’t we think that way more often? I think that one reason is that economists *always* think in terms of tradeoffs, because in economic theory if there’s a win-win move to be made, we’ve already made it. As economists say, people don’t leave hundred-dollar bills lying on the street. Which isn’t wrong as a rule of thumb, but economists like to make rules of thumb into eternal principles. So if we assume that the savings aren’t there, we don’t look for them, and we wind up living in a world of $100 bills, only slightly hidden, that we don’t pick up.