Consumers who fully charge their iPad tablet every other day can expect to pay $1.36 for the electricity needed annually to power the device, according to an assessment by the Electric Power Research Institute (EPRI).

The analysis shows that each model of the iPad consumes less than 12 kWh of elelctricity over the course of a year, based on a full charge every other day. By comparison, a plasma 42” television consumes 358 kWh of electricity a year. EPRI conducted the analysis in Knoxville, Tenn., at its power utilization laboratory. Costs may vary depending on what region that a consumer resides and the price of electricity in a particular location.

The assessment was conducted to determine the load requirements – the amount of power needed to operate the devices -- of the increasingly popular iPad. According to Apple, 67 million of the devices have been purchased worldwide.

EPRI calculations show that the average energy used by all iPads in the market is approximately 590 gigawatt hours (GWh). In a scenario where the number of iPads tripled over the next two years, the energy required would be nearly equivalent to two 250-megawatt (MW) power plants operating at a 50 percent utilization rate. A quadrupling of sales in two years would require energy generated by three 250-MW power plants.

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The EPRI analysis shows that the Apple iPhone 3G consumes 2.2 kWh of electricity each year, which results in a power cost of $.25 annually.

Other products that were included in the analysis were laptop PCs, which consume 72.3 kWh of electricity each year and cost consumers $8.31 and 60W CFL light bulbs which consume approximately 14 kWh of electricity and cost consumers $1.61 a year.

For the sake of comparison: A 60-watt compact fluorescent bulb will set you back $1.61, a desktop PC will cost you $28.21, a laptop PC is $8.31—and you’ll fork over $65.72 to power the office refrigerator.