The metric, put out this week by energy analytics company Opower, is based on the assumption that iPhone owners will recharge their device once a day for the entire year:
Phone 5: consumed 9.5 watt-hours to charge, taking 1 hour and 50 minutes. Maximum wattage was 6.3 watts, with an average of approximately 5.0 W. Multiplying 0.0095 kWh/day by 365 days = 3.47 kWh per year. Annual charging cost is projected to be $0.41/year.
To recap: the iPhone 5 is rated for 8 hours of talktime over 3G, up to 8 hours of Internet use over 3G and LTE/10 hours by Wi-Fi, and up to 10 hours of video playback. All these numbers come from Apple's own specs. In , we got anywhere from 7.25 to 8.48 hours of talk time, depending on the carrier.
The estimate follows one from The Electric Power Research Institute published in June, which pegged the annual energy cost of a third-generation iPad at $1.36. That same study estimated the cost of the iPhone 4 (the iPhone 5's predecessor) to run a slightly lower 38 cents.
In all cases, that annual cost of charging is dwarfed by the up-front cost of the device, which for the latest iPad is $499, and on $199 for the iPhone. In the iPhone's case there's also service, which can be thousands of dollars over what is typically a 24 month contract.
In a post on the findings, Opower says the iPhone beat out its main competition, Samsung's Galaxy S3, which is estimated to cost 53 cents a year worth to keep charged due to its larger battery.
"The paramount point here though is not the difference between the two phones, but rather their striking similarity: the energy consumption of a modern smartphone is minuscule," Opower's Barry Fischer wrote.