The biggest energy and environmental impact of using Google and other internet services may not be where you think it is. The rapid spread of large data centers that power the internet is responsible for a growing energy use and share of carbon emissions. It is tempting to jump to the conclusion that the internet and all its services stand in the way of energy and environmental sustainability. Not necessarily so!
Google recently released the environmental footprint of several of its data centers and “cloud” services. First, let’s give Google kudos for its transparency: disclosing the energy footprint of web services is critical to enable users to hold their service providers accountable for minimizing their environmental impact, as well as to manage their own footprint. Google’s energy use and carbon emissions numbers seem huge in aggregate, but much more modest when considered from the perspective of individual users.
Adding up Google Search, Gmail and YouTube, a simple calculation shows that the “cloud” footprint of Google services would be approximately 7.4 kWh annually. This is less electricity than a typical DVR consumes in just 9 days! The reason is that each search uses a tiny fraction of a data center’s capacity for a very short period of time.
On the other hand, the biggest share of your internet energy use may lie right in your home: all the resources and energy use of the device you are using to access the internet are fully dedicated to you. Some of the “client” devices, such as smart phones and tablets, are very energy efficient and use very little energy. However others such as typical desktop PCs and their displays, and even notebook PCs use much more energy than your share of Google’s data centers.
The annual energy footprint of a typical desktop and its display, and even that of a notebook, may be 10 to over 40 times larger than your Google footprint! 
To be fair, tablets and computers are used for many other things than Google searches, email and videos. Typical users also use web services from other internet companies, watch movies, play games, edit documents etc. However even if you multiply the typical Google footprint by a factor of 5 to account for all internet activities, the cloud part of your computing energy use remains much lower than that of your desktop and associated display, or your notebook.
Not all PCs are energy hogs: the most efficient desktops and notebooks can use as little as 1/5th of the average PC. You can reduce your energy use and save money by choosing Energy Star computers, displays and other equipment. And if you want to buy the best of the best devices on the market from an energy efficiency perspective, check out Top Ten USA (http://www.toptenusa.org/) which tracks the top ten most efficient products in the US in each product category.
On the other hand, beware of some of the cheapest equipment, and ask for their energy use. Some entry-level computers use cheap and inefficient components to save a few cents on the purchase price, but they will end up costing you $50-$100 or more in extra electricity costs over their lifetime. As mobility-optimized tablets and to some extent notebooks demonstrate, there are many opportunities to make computers more energy efficient, such as graphics cards that don’t guzzle power in idle mode when there are no graphics to process, more efficient power supplies, processors, memory, disks etc. The technologies exist and save users money from reduced electricity bills.
Lastly, check that your power management settings are enabled (Windows: Power Options in Control Panel, Mac: Energy Saver in System Preferences). Ensuring the computer automatically goes to sleep when not in use is the single biggest energy saving opportunity on most computers, and it won’t cost you a dime.
Happy internet use!
 Annual energy use for a hypothetical Google user who performs an average of 10 searches per day and watches 1 hour of YouTube videos per day, in addition to a typical use of Gmail:
Note that although this does not include other Google services such as Maps, Picasa, Google+ etc, this number may be higher than the energy use of an average Googe user: Google estimated 2.26 kWh annual energy use per user for all its services in 2010.
 Tablet is an iPad. Notebook and desktops are based on representative mid-range configurations and typical usage patterns.