- ``US physicist Alex Wissner-Gross claims that a typical Google search on a desktop computer produces about 7g CO2.
- ``However, these figures were disputed by Google, who say a typical search produced only 0.2g of carbon dioxide.''
My own rough back of envelope guess came out in between Wissner-Gross's assertion and Google's...
Here's how I worked it out:
- according to a google search(!), google has about 700,000 servers.
- let's guesstimate the power to run a server and all its plumbing: 250 W.
- google received 90 million searches per day in 2006
and 1200 million per day in 2007...
- Hmm, this growth rate is big enough that it is going to be hard to get a trustworthy answer!
- Well, let's multiply 700,000 servers * 0.250 kW * 24 hours per day / 1200 M searches per day -
that is 0.0035 kWh per search; 0.007 kWh for a pair of searches; and 3.5g of CO2 for a pair of searches. (Assuming that electricity has a footprint of 500 g per kWh.) [In fact I think I heard that google has lots of servers in Iceland, where the electricity footprint is much smaller.] Meanwhile, boiling a 250 ml cup of water uses about 0.028 kWh. So my estimate is that the energy cost of two google searches (measured at the googleplex alone) is about one quarter of the energy cost of boiling a cup.
This calculation has not included the energy cost of running your own desktop computer, wireless, and modem for the duration of the search too; nor the cost of running the internet twixt you and google. If it takes you one minute of computer time to do the search, and if your computer and peripherals use 120 W, then the cost of your computer's power in that duration is 0.120 kW * (1/60) hour, which is an extra 0.002 kWh.
Here's the bottom line from my rough guesses: the total energy cost of the pair of searches seems to be about 0.01 kWh. That's exactly the same as the energy used by leaving a phone charger plugged in for one day. Which is also the same as the energy used by driving an average car for one second.