Earlier this year Google blogged about the amount of energy used in one Google search.
Their engineers crunched the numbers and found that an average query uses about 1 kJ of energy and emits about 0.2 grams of carbon dioxide. But those raw numbers don't really put the environmental impact of searching the Internet into perspective. To add some context, below is data about the C02 impact of some everyday activities and items compared to Google searching:
|CO2 emissions of an average daily newspaper (PDF) (100% recycled paper)||850|
|A glass of orange juice||1,050|
|One load of dishes in an EnergyStar dishwasher (PDF)||5,100|
|A five mile trip in the average U.S. automobile||10,000|
|Electricity consumed by the average U.S. household in one month||3,100,000|
Making one cheeseburger uses as much energy as 15 000 web searchers! But I have to say a cheeseburger tastes better. You can read Energy and the Internet on the Official Google Blog.