Energy Efficient Computers

This desktop is Energy Star qualified and rated EPEAT Silver
This desktop is Energy Star qualified and rated EPEAT Silver

Computers are ubiquitous in modern life, with 72% of all employed adults using a computer at work, and Californians having an average of 0.9 desktops and 0.5 laptops per household. That adds up to over 29 million computers statewide. The average corporate desktop and laptop require about 700 and 87 kilowatt-hours to operate each year, respectively, and the average home desktop and laptop require about 284 and 48 kilowatt-hours to operate each year. Adding that up, total computer (including monitor) energy consumption is about 7 Terawatt-hours each year, equal to the annual energy output of 2 coal plants.

Fortunately, there are many ways to increase computer energy efficiency. Here are some of the biggest opportunities:

  • Implement power management systems to automatically turn off computers and monitors when they are not in use
  • Reduce "idle" power consumption - the power used when the computer is turned on, but is not actively processing new information
  • Increase power supply energy efficiency
  • Reduce component power consumption - efficient case fans, hybrid or flash hard drives, using one larger memory chip instead of multiple smaller ones, and other minor upgrades can improve efficiency yet have neutral or even positive impact on performance
  • Purchase laptops or laptop-style compact desktops - laptops are optimized for long battery life, which means they are also more energy efficient than desktops
  • Purchase a more efficient monitor - LCD monitors use much less energy than CRTs, and Energy Star qualified monitors can use 25-60% less energy than standard models.

There still remains an enormous potential to reduce computer energy consumption. If new software and upgraded computers are able to reduce computer energy use by 75% - a very achievable goal - Californians will save 5.2 Terawatt-hours of electricity per year, enough to power over 880,000 homes.

Photo Credit:  Courtesy of Sony Electronics; Sony JS Series

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This ultimate efficiency computer can save nearly 70% relative to the Energy Sta
This ultimate efficiency computer can save nearly 70% relative to the Energy Star standard
Ultra-Efficient Computing

In 2007, Ecos Consulting, the Electric Power Research Institute, and the California Energy Commission decided to test the limits of energy efficient desktop computers. Focusing on reducing power consumption during idle and active modes, their goal was to create both market-ready and ultimate-efficiency computers that would still have good performance.

The team started by selecting the most efficient available motherboard and chips - one of the most important steps in creating an efficient computer. They used processors that can dynamically scale performance to match program requirements, saving energy when processing demands are low, and selected components with low electrical losses.

Next, the team reduced idle power consumption by an additional 25-36% by selecting efficient components. 80 Plus certified power supplies and efficient case fans saved about 7 Watts. Using a single, larger memory chip instead of two smaller ones saved another 1 or 2 Watts, without impacting performance. The team also specified a hybrid hard drive, which supplements the traditional spinning disk with a flash buffer, saving 5 or 6 Watts. New, flash-only hard drives, which have emerged since this research was completed, can save even more energy by eliminating the spinning disk altogether. Plus, these hard drives are faster than traditional hard drives, improving performance.

Putting everything together, the team found that nearly all of their prototypes had sufficient performance to run typical office software under the Microsoft Vista operating system, while consuming 40 to 70% less energy than Energy Star qualified computers.

This translates into a huge savings potential: if all U.S. enterprises adopted the ultimate efficiency computer, corporations could eliminate 11.2 million tons of CO2 emissions, save 16.7 billion kilowatt-hours, and save $1.67 billion in electricity costs.


EEC chart

Computers spend most of their time in idle mode, and efficiency improvements in this mode do not impact processing performance, so idle mode savings are an easy way to make a big impact.


Photo and Chart Credit:  Courtesy of the California Energy Commission and Ecos Consulting

This notebook is rated EPEAT Gold, the highest possible sustainability ranking
This notebook is rated EPEAT Gold, the highest possible sustainability ranking
Sustainable Procurement


At the heart of Silicon Valley, the businesses and residents of San Jose are at the forefront of computing. And as one of the ten largest cities in the United States, the City of San Jose is itself a major user of computers. So it's not surprising that as part of its sustainability initiatives, the City of San Jose decided to push the envelope in sustainable computing, becoming the first city to require purchase of EPEAT qualified computers.

San Jose was drafting an RFP for computer purchases in early 2006, just as the EPEAT standards were finalized. Even though no products were yet officially certified, they knew that about 60 models would qualify, so they decided to insert the requirement into the RFP. The requirement was a great success, and has been standard practice in the city ever since.

The city likes the EPEAT system because there are many qualified models available, there are measurable benefits, the standard covers all aspects of sustainability, and the requirement is easy to specify & implement. Plus, the city has found no difference in performance between EPE