Any time you make a purchase, it’s always good to know what extra costs will come with it. After all, every purchase comes with its own little (and sometimes not so little) hidden extras. Stuff you’ll have to pay for to make the initial purchase worth it. Buying a car comes with a whole host of extra expenses: maintenance, gas (which is a big deal, what with gas being about a zillion dollars these days), pink fuzzy dice for the rear view mirror, that sort of thing. It’s the same with gadgets. If you buy an iPad, for example, you’ll probably want a case, then you’ll want a screen protector, then you’ll have to spring for some decent apps from the App Store (which can add up in a great big hurry). All in all, buying the cheapest new iPad available will run you $500 (plus tax and AppleCare, if you want it), but all the extras tack another $40-50 onto the price, at least.

But there’s another extra cost, one that people don’t usually think about: electricity. Any device you buy has to have electricity. Without it that iPad becomes an oddly shaped (and ridiculously overpriced) frisbee. Or a clipboard (without the clip), or a Clint Eastwood-style bulletproof plate under your tunic during a gunfight (I don’t recommend trying that one). What’s more, unless you’re using a really high-quality solar charger, that electricity costs money.

So that raises an interesting question: just how much money does it cost you to charge up that fancy new iPad? Well, according to data released by the Electric Power Research Institute, the answer is $1.36 per year. That’s right. If you’re diligent and attentive enough, you could conceivably pay for your iPad’s electricity needs with change you find on the ground. EPRI conducted the study at their labs in Knoxville, Tennessee. There they found that fully charging the iPad every other day will use a total of about 12 kilowatt hours of electricity in a year. To put that in perspective, that shiny 42-inch plasma TV hanging on your wall will burn through 358 kilowatt hours in the same amount of time.

Of course, the actual cost of the electricity used will vary depending on where you live. Those twelve kilowatt hours may cost you a few cents more here or a few cents less there. Whatever the actual number in your market, though, it’s not going to be high. In other words, while the cost of gas might make you think twice about buying that ginormous SUV, the cost of electricity shouldn’t give you any second thoughts about buying an iPad.