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. ... 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.
I hadn't thought of it much before, but one of the benefits of consumers' massive shift toward mobile computing is the decreased power consumption of battery powered devices that are energy efficient by necessity. Laptop PCs are more efficient than desktops, and as this EPRI study shows, tablet devices like the iPad use one sixth of the energy of your average laptop, while smartphones burn even a fraction of that.
Individually the power/money saved doesn't look like all that much compared to the hardware and network costs of the devices, but collectively even a modest shift of usage from traditional PCs to low-power mobile devices can add up to a substantial reduction in global energy consumption.