Google fires back on energy use claims

The news was all over the blogosphere this weekend: Doing two web searches on Google creates enough carbon dioxide to boil a kettle.

It was based on an article in the Times of London (and so now the kettle of tea comparison make sense), which reported on a Harvard researcher's study of the environmental impact of computing.

The energy used to complete a search was explained thusly:

... its search engine generates high levels of CO2 because of the way it operates. When you type in a Google search for, say, “energy saving tips”, your request doesn’t go to just one server. It goes to several competing against each other. It may even be sent to servers thousands of miles apart. Google’s infrastructure sends you data from whichever produces the answer fastest. The system minimises delays but raises energy consumption. Google has servers in the US, Europe, Japan and China.

On Google's official blog, the senior VP of operations, wrote that 7 grams per search is way too high, because Google is so fast. The actual figure, he said, is about 0.2 grams per search.

Queries vary in degree of difficulty, but for the average query, the servers it touches each work on it for just a few thousandths of a second. Together with other work performed before your search even starts (such as building the search index) this amounts to 0.0003 kWh of energy per search, or 1 kJ. For comparison, the average adult needs about 8000 kJ a day of energy from food, so a Google search uses just about the same amount of energy that your body burns in ten seconds.

Your own computer, Google says, will use more energy than Google uses to answer your query in the time it takes you to do the search. And, the company says its datacenters are among the most energy efficient in the world.

Alex Wissner-Gross, the Harvard physicist responsible for the study that rattled all those kettles, has set up a site to help companies make their own websites as carbon-neutral as possible.

But according to the Times' article, Google's still pretty mild, whether it's causing 0.2g or 7g of CO2 to be released per search. Running the average PC is 40-80g per hour. And an avatar in Second Life? A whopping 1,752kwH of electricity a year — almost as much as the average Brazilian uses.