Some tweets last night written by Danny Bradbury asking about the energy consumption of mobile phones alerted me to GreenYourPhone, a scheme cooked up by Boulder, Colorado-based Renewable Choice and the electronics chain Best Buy. For $10, you can salve your conscience over the amount of CO2 your talk and text habit produces.
The FAQ on the GreenYourPhone site claims a pair of mobile phones chews through 500kWh (kilowatt-hours) of electricity over a period of two years but is sketchy on where the figure comes from. The page cites Ericsson and Nokia studies but without links. Until Colorado wakes up, it's hard to check. But, looking at the last known studies from Ericsson, I reckon they are using this summary, which claims the amount of CO2 thrown out by the entire mobile network per subscriber per year was 54kg in 2002, falling to 38kg in 2005.
To get to how many kilowatt-hours you need to produce that CO2 you need to divide by around 0.4 if you use the older 54kg figure, which is what I think GreenYourPhone did. This approximates roughly to the mix of coal- and gas-fired power plants found in a country like the US. For every kilowatt-hour of electricity, you produce 0.4kg of CO2. If you use the more up-to-date figure – and efficiency in the network keeps improving, although 3G will never be as power-efficient as GSM – you get to 95kWh.
If you think 125kWh per phone per year sounds a bit steep when the battery stores less than 4Wh – a full charge every day for a year is still only 1.5kWh – the amount does not just over the phones or the energy needed to make them, it accounts for all the equipment that connects them together when you make each and every call.
Even so, GreenYourPhone does fairly well out of the deal. Taking a look at carbon-offset costs, you could cheerfully buy credits for up to five years' worth of calls by shopping around. Offset costs run to between $5 and $30 for a whole metric tonne of CO2. Compare that to $10 for a fifth of that amount. You get a sticker though and "your purchase helps schools" on account of some of them having wind turbines installed.