Charging an iPad up to 100 percent every other day will consume less than 12 kilowatt-hours (kWh) of electricity in a year, according to an analysis by the Electric Power Research Institute (EPRI). Using the national average electricity rate, that adds up to $1.36.

A dollar and change might not sound like a lot, but it adds up. All 67 million iPads put together, from the first generation in 2010 to the newest edition introduced this year, consume as much power as 3,000 U.S. homes, thApple iPad newse executive summary of the full research report said. That’s 590 gigawatt-hours.

The newest iPad, at 11.9kWh per year, uses about 50 percent more power than the first generation’s 7.2kWh because of its faster dual-core processor. It also costs more power than an iPhone 4 ($0.38 per year) or iPhone 3G ($0.25 per year).

When viewed in comparison to other computing devices, however, the iPad looks like a straight-up bargain. The EPRI estimated a laptop computer to cost $8.31 per year and consume 72.3kWh of electricity per year, while a desktop would cost $28.21 and consume 245.5kWh.

They all beat out household appliances. The most costly item tested by the EPRI was a clothes dryer, which added up to $105.82 and 921kWh for a year of use; a refrigerator with 21 cubic feet of storage space would cost $65.72 (572kWh) and a dishwasher would cost $34.47 (300kWh).

One device that used about the same amount of energy as the iPad was a compact fluorescent light bulb, which would cost just $1.61 per year and use 14 kWh, compared to its 60-watt incandescent equivalent at $7.58 and 66kWh. It looks like you can save about the same amount of energy switching from a laptop to a tablet as you can by replacing your light bulbs.

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