Measuring the CO2 of a Google search: Half a cup of tea, or 10 seconds of existence?
There was an article in the London Times this weekend on the energy footprint of various forms of Web activity. For example, according to the website CO2Stats, a single Google search generates 7g of CO2, compared to about 15g to boil water to brew a cup of tea.
Google, which is very proud of its relatively energy-efficient data centers, was obviously stung to the quick, and fired back in its corporate blog:
"[The Times article claimed] that a typical search uses "half the energy as boiling a kettle of water" and produces 7 grams of CO2. We thought it would be helpful to explain why this number is *many* times too high. Google is fast — a typical search returns results in less than 0.2 seconds. 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.”
The two sides have a significant difference of opinion about how to measure power consumption. Google’s analysis emphasizes the speed of its search, while the number referred to in the Times article apparently factors in the additional power needed to deliver a search result from a server located on the other side of the world.
There is little consensus on how to measure data center power efficiency, at least in part because it’s hard to define the amount of “work” accomplished per unit of power. The Data Center Efficiency Program, part of the Energy Bill (H.R. 6) creates an IT industry-led program to develop metrics and best practices for data center energy efficiency. Energy Star also is working on developing metrics for data center efficiency.
UPDATE: According to Harvard University physicist Alex Wissner-Gross, the creator of the CO2Stats website, the Times came up with the 7g figure all on their own. The only quotes they correctly attributed to him were, "A Google search has a definite environmental impact" and "Google operates huge data centers around the world that consume a great deal of power."
I doubt if it’s all a plot on the part of the Times to focus attention on the need for a methodology to measure the power efficiency of an industry that’s a significant consumer of electricity, but that could be an unintended consequence of this tempest in a teapot.