An interview with Bill Weihl, Google's director of Energy Strategy, reveals much about Google's thinking on energy matters and re-iterates the firm's desire not to compromise its competitive position by revealing carbon emissions information that could reveal sensitive aspects of its IT infrastructure to competitors.

TW: What is Google's carbon footprint? Is it the largest IT emitter of carbon save for chip foundry concerns such as Intel?

Bill Weihl:

Google has partnered with the Environmental Resources Trust to have the company's carbon footprint independently certified, and will continue to do so yearly. As a result of our efforts to account for our carbon footprint and certification by the Environmental Resources Trust, we do not believe that we are the largest IT emitter of greenhouse gases. However, we do not disclose our carbon footprint or our energy consumption. These are key competitive elements of our operational infrastructure.

TW: What proportion of Google's energy requirements come from renewable energy resources? What proportion comes from oil, gas or coal-fired power stations?

Bill Weihl:

We strive to find and use renewable energy where we can. In addition, we are working to develop and encouraging our energy providers to develop additional renewable energy resources and have committed to creating an additional 50MW of renewable energy generating capacity by 2012. Finally, we have installed corporate America's largest solar panel in our Mountain View, CA headquarters. Again, for competitive reasons, we do not disclose the specific details of our energy portfolio.

TW: Is Google on track to being carbon neutral by the end of the year?

Bill Weihl:

We will be carbon neutral for 2007, and will achieve this through a combination of energy efficiency investments - many of which we have already made - renewable energy, and high quality offset projects. We have already invested in some offset projects, including the destruction of agricultural methane, and will invest in more over the course of 2007 to offset our entire greenhouse gas footprint for 2007.

TW: What sum will be spent by Google on carbon offsets?

Bill Weihl:

We cannot disclose this information.

TW: Approximately how many servers does Google have. My own estimate is of the order of half a million?

Bill Weihl:

Fast, innovative products are crucial for our users and require significant computing power. As a result, Google invests heavily in technical facilities and has dozens of facilities around the world with many computers. However, for competitive reasons, we don't disclose exact numbers of facilities or computers.

TW: What power-efficiency measures do Google data centres apply: hot aisle/cold aisle design; high-efficiency UPS', etc.?

Bill Weihl:

Our servers are among the most efficient in the industry, using high-efficiency power supplies, high-efficiency DC-DC converters, and numerous other technologies to reduce power consumption. Because of this focus on efficiency, Google's servers have been more than 90 percent efficient since 2003. Most computers waste a third to one half of the power they consume.

Our data centres incorporate a number of innovations in cooling and backup power to eliminate much of the overhead normally associated with those and, as a result, Google's data centres use half as much power as the industry average.

We may discuss additional details of these innovations in the coming months, but do not have anything to announce at this time.

TW: Do you use the Green Grid measures of PUE and DCE? If you do what are the numbers?

Bill Weihl:

We do use these measures internally, but are not disclosing these details at this time. We may discuss this publicly in the coming months, but do not have anything to announce at this time.

TW: Will the Mountain View solar power scheme be extended to other Google datacentres?

Bill Weihl:

Our 1.6 MW solar installation in Mountain View -- the largest single corporate installation in America -- is just a first step in our use of renewable energy. We have committed to developing at least 50 MW of new renewable generation by 2012.

TW: The Carbon Disclosure Project has made various suppliers' carbon footprint numbers available for CY 05: Dell; Cisco; HP, IBM; Intel; and Microsoft. How does Google measure up against these suppliers in absolute carbon footprint terms?

Bill Weihl:

Please see the answer to no. 1. For the same reason, we cannot discuss where we rank against each of these companies, since that would likely be tantamount to disclosing our actual footprint.

TW: Does Google agree that comparing IT suppliers on absolute carbon emissions ratings is inappropriate and due account has to be taken of different business models, such as computer-intensive, people-intensive, manufacturing-intensive, etc. What thoughts do have about trying to calculate a method of carbon emission comparison that reflects these differences?

Bill Weihl:

Simply comparing the absolute carbon emissions is like comparing apples and oranges. If a company does twice as much business as another, one might expect it to have higher emissions. So absolute emissions numbers on their own are not very useful.

Some have proposed measuring "emissions intensity", perhaps as a function of revenue or net profit, and measures like that might prove to be a reasonable approach over time. In the end, though, what matters is that we as a society reduce our emissions.

This will require us all to become more efficient in how we use energy -- something that we at Google believe we have done better than anyone, and something that we are working with our partners in the industry (for example, through the Climate Savers Computing Initiative) to enable everyone to do. It will also require much more extensive use of renewable energy -- something that we have already taken major steps toward, and have committed to even more extensive use of in the future.


Google is clearly extremely serious about reducing its greenhouse gas emissions and about being a sensitive friend to the environment. It is also competing in a strongly fought-over market where IT infrastructure size, power and distribution are closely-guarded secrets. One has to respect that.

A benefit of the Green Grid's PUE and DCE measures will be that it will be possible to compare suppliers' datacentre infrastructure on these metrics without disclosing indications of the datacentre numbers, size or contents.