Every night, I sleep beside a mess of power cords and cables that I'm sure is some serious fire hazard. Beside my bed, I charge at least three phones and one tablet every night, and in my office, there might be a laptop, another tablet and possibly some other phones on charge.

With so many battery-powered devices that constantly need to be charged, it's a legitimate concern to worry about how much your mobile devices are costing you each month and year on your power bill. Could a single tablet cost your upwards of $100 every year to power? $200? More? What about your smartphone? Your spouse's? What of you have a family of iPads?

I have never put much thought into it, considering my gadget habits are a little excessive to begin with. I'm positive I spend more on just about every front (monthly wireless bills, devices, cases, etc.) when it comes to mobile tech than the average consumer. So what's a little more money spent to power my favorite gadgets?

But I do recall being a bit curious over how much it might cost to continuously power the new iPad. Mobile devices are constantly becoming more advanced and, in turn, more powerful. To keep the new iPad and its unbelievably crisp display powered for Apple's standard of 10 hours (of usage), it nearly doubled the battery capacity and wattage of the new iPad. The iPad 2 from last year housed a 6944mAh (25W) battery, while the new iPad is equipped with a 11,666mAh (42W) battery. Comparing that to the average smartphone battery, which is less than 2,000mAh, there is good reason to be concerned over its power consumption and just how much it's costing you each year to keep it powered.

According to research conducted by Electric Power Research Institute (EPRI), a non-profit research and development group, some gadgets are costing you far less to power than you might think. Various gadgets cost users less than a cup of coffee to fuel all year long, particularly those made by the Cupertino-based firm.

So how much does it cost to power an iPad for an entire year? Based on the U.S. average residential price of 11.49 cents per kilowatt-hour, EPRI estimates $1.36 is the magic number. That number is also based on a full charge (from 0 to 100 percent) and the assumption that the average user might only charge their iPad every other day. Perfectly plausible. I'm a heavy user and I don't always charge my iPad every day.

Comparing that number to the average power consumed by other common household gadgets, the iPad is very power efficient – much more so than I would have imagined. A 60-watt compact fluorescent bulb is estimated to cost $1.61 annually. A desktop PC? $28.21. And a refrigerator sets the average user back $65.72. "If the number of iPads triples from the current 67 million, they would need the electricity from one small power plant operating at full strength," says Jonathan Fahey of the Associated Press.

Apple's iPhone 4 is also pretty light on the power consumption, costing only $0.38 annually, on average.

Baskar Vairmohan, the researcher who performed the study on the iPad, explained that EPRI is now trying to determine if the sudden popularization of iPads and other tablets is adding to or reducing power consumption. Judging by how much more power efficient the iPad is than your average PC, I'm willing to bet overall power consumption is on its way down. Fahey agrees, saying:

"But if people are using iPads instead of televisions to play video games, or ditching their desktop computers for iPads, the shift to tablets could mean lower overall power consumption. A desktop computer uses 20 times more power than an iPad."

I am also willing to bet that I have cut my personal power consumption significantly over the last few years. People ask me why I prefer to use a tablet over a laptop to work if I still have to use a laptop for a portion of the work. My answer always varies as there is no one reason. But a but factor in that is battery life and power consumption. I can get through an entire day of work without having to charge anything if I use both my iPad and MacBook Air. If I used just the MacBook, it would have to be charged at least twice before the day is through. Granted, I have never done this with the cost of power in mind. But making it through an entire day without needing an outlet is irreplaceable.

EPRI's average cost of a year's worth of powering an iPad, $1.36, probably doesn't apply to me. (It likely costs me double that.) And it says nothing about non-Apple tech. But it's comforting to know I'm not paying oodles more each year just to keep my phones and tablets charged.

Tell me, folks. Does it surprise you that it costs so little to keep your iPad charged each year? Do you find the number to be improbable? How much would you have figured it costs you each year to keep all of your gadgets charged? I figured it was at least in the hundreds. Oh, how wrong I was …