Q: How much energy does a typical laptop and desktop use in standby mode? How has this been reduced over time by changes in technology?
Asked by Shiva Swaminathan, Fremont, Calif.
More powerful computers use more energy, because of their faster processors and graphics cards. Standby mode helps reduce this energy consumption greatly. However, even in standby mode, computers still consume 1-60 watts of energy. This is because most modern devices use AC/DC adapters with transformers that consume power even when the device they are attached to is not drawing any current. Also, many devices draw a little bit of power during standby to enable them to switch back on quickly when you need to use them. This is especially true for devices such as laser printers that would otherwise take quite a while to warm up.
Different computers consume different amounts of power during standby, based on how many of their components they can switch off. In older computers, only the hard disks were turned off during standby, whereas in newer computers almost every hardware component switches off. Also, laptops are designed to be more efficient than desktops, to boost battery life.
However, peripherals such as monitors and printers continue to draw power even when the computer is on standby or switched off. Larger and higher-resolution monitors use more energy than smaller and lower-resolution ones. Older cathode ray tube (CRT) monitors consume more power than flat-screen liquid crystal displays (LCDs), particularly those powered by highly efficient light-emitting diodes (LEDs). Printers are another source of energy drain. In general, the faster and higher-quality a printer, the more energy it uses. Thus laser printers use a lot more energy than inkjets, both when actively used or during standby.
Practical concerns of standby power consumption
A good reason to switch off computers and their peripherals is to increase their life span. This wasn’t true of most computers before the ’90s. The power surge caused by turning those systems on and off would damage internal components. Modern computers automatically protect their components from abrupt loss of power. In fact, switching off current computers can actually prevent some of their components, like their fans and hard disks, from wearing out quickly.
Then again, constantly switching off one’s computer means waiting several minutes for it to turn back on again. This is certainly not as convenient as standby mode, especially given that most people’s workdays are busy enough as it is. Also, many computer systems these days automatically download security updates and are backed up to a central server. Shutting them down even after office hours or on weekends may interfere with these processes. Printers, too, are hard to switch off in a networked office where many people use the same machine. At least monitors restart quickly and can be conveniently turned off to save power. This is a much better idea than using screensavers, which were developed for older monitors where an image would burn into the screen if it remained still for too long. These days, using a screensaver just keeps the monitor on and drawing full power even when it’s not in use.
Other useful information
Energy Star and Climate Savers Computing both provide websites to find efficient computer products. You can also look for the Energy Star logo, or its equivalent in the United Kingdom, the “energy saving recommended” logo. The Energy Star website also provides help with adjusting your computer’s power management settings.
A watt meter provides a simple way to test how much power your computer is using. Some easy-to-use ones are the “Kill A Watt” and “Watts up” brands. These can help analyze the energy usage of different computers and peripherals during standby mode, and determine which ones should be switched off or be replaced with more energy-efficient models.
I used a Kill A Watt meter to test the power usage of several Stanford computer configurations both when they were on and during standby. The results are summarized below:
Stanford on standby
Stanford is attempting to reduce even the little energy used during standby mode. According to Fahmida Ahmed, Manager of Sustainability Programs, Stanford is looking into encouraging users to turn off machines not in use. Since this gets into influencing individual behavior, Stanford is currently piloting the process in a few places to determining the best practices.
Stanford is also trying to increase the number of computers actually using the BigFix Power Management Tool. “Out of 25,000 BigFix installations, only about 7,500 have turned on BigFix Power Management,” says Joyce Dickerson, director of Sustainable IT at Stanford. “Different schools and departments have chosen different methods, and that has shown very different results.” Currently departments that enable power management centrally have about 80 percent deployment. Unfortunately, those that allow users to self-select whether to enable it or not have very low numbers. There hasn’t yet been much marketing to the self-selecting group, so this is looked up as an opportunity to greatly increase the use of power management.
Effect on carbon emissions
The energy savings resulting from having a computer on standby versus being left on all the time can result in approximately 449 pounds less CO2 entering the atmosphere every year. This is equivalent to preventing the burning of 23 gallons of gasoline a year. This is just for a single computer, and clearly this can make huge impacts for institutions like Stanford that use thousands of computers. Imagine the impact on all of Silicon Valley! (Calculation based on PG&E Carbon Footprint calculator, and computers using ~98 more watts of power when not on standby.)
Cost issues
Newer computers, peripherals and power strips can be expensive. However, there is a saving of about 40 cents for every day that a computer is on standby (~3 watts) instead of being left on (~101 watts). This can quickly add up over time to a savings of about $147 a year for a single computer, based on PG&E’s current average total rate of ~$0.171 per KWh used.
Rules and regulations
There are no laws regulating standby power usage for private citizens and companies in the United States. However, in July 2001 President Bush signed Executive Order 13221 on “Energy Efficient Standby Power Devices,” stating that all government agencies should purchase products that consume no more than 1 watt in standby mode.
In 2005 the European Union implemented the “Framework Directive on the Eco Design of Energy-Using Products (EuP),” intended to increase energy savings from all consumer appliances. The EU has announced plans to bring in legislation that would limit computer standby power use to 1 watt by 2010. The United Kingdom is considering similar laws.
Sandeep Ravindran is a PhD candidate in microbiology and immunology.
