Google has denied claims that just two searches on its site uses the same amount of energy as boiling a kettle.

Recent research by Harvard University physicist Alex Wissner-Gross suggested that each Google search produces around seven grams of CO2, roughly half that produced by boiling a kettle.

"Google operates huge datacentres around the world that consume a great deal of power," said Wissner-Gross. "A Google search has a definite environmental impact."

However, Google rubbished the findings in a recent blog posting, providing its own substantially lower figures, and adding that during the time it takes to do a Google search "your own personal computer will use more energy than Google uses to answer your query".

"Google is fast - a typical search returns results in less than 0.2 seconds, " wrote Urs Hölzle, senior vice president for operations at the search firm.

"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 0.0003kWh of energy per search, or 1kJ."

According to Hölzle, this is roughly equivalent to the amount of energy the human body burns in 10 seconds. "In terms of greenhouse gases, one Google search is equivalent to about 0.2 grams of CO2," he wrote.

Hölzle also pointed out that Google is investing heavily in greater energy efficiency as well as cleaner energy sources.

"In 2008 our philanthropic arm, Google.org, invested $45m [£30m] in breakthrough clean energy technologies. And last summer, as part of our Renewable Energy Cheaper than Coal initiative, we created an internal engineering group dedicated to exploring clean energy," he added.

However, Wissner-Gross maintained that our increasingly connected lifestyles could begin to take their toll. Just viewing a web site generates between 0.02g and 0.2g of CO2 per second, depending on the amount of rich media embedded on the page, he claimed.

The environmental impact of the IT industry has been a matter of much debate in recent years, with analyst firm Gartner calculating that the industry accounts for around two per cent of the world's energy usage.

Several initiatives have been created to try to minimise the impact of IT on the environment, including the WEEE directive, which controls the disposal of electronic goods in Europe; CO2stats, which Wissner-Gross helped to create; and the Climate Savers Computing Initiative, which Google co-founded in 2007.