Standby power

Standby power, also called vampire power, phantom load, or leaking electricity, refers to the electric power consumed by electronic appliances while they are switched off or in a standby mode. A very common "electricity vampire" is a power adapter which has no power-off switch. While this consumption of power may be used to provide useful functions for appliances such as remote controls and digital clocks to the user, most power consumed by non-operational devices is considered wasted. Advocates of energy conservation sometimes use the term "wall warts" to describe devices that stay plugged in and using power without performing a useful purpose.

Definition

Standby power is power that is consumed by electronic equipment while in a power-off state.

Some devices continue to consume power while in a power-off state for legitimate purposes, such as a clock or infra-red receiver required to reactivate the device. Other devices consume power for no useful purpose, such as a plugged-in laptop power adapter which is not connected to the laptop.

Devices and functions that consume standby power

• Power supplies, transformers and ineffective electronic devices, for example battery chargers. Those constantly generate heat that can't be further used.
• "Instant on" functions, like remote control receivers, waiting for the user to interact.
• Displays and condition indicators, such as clocks, temperature gages and status indicators, for instance the standby LEDs on electronic devices, although the power used by such indicators is very small (milliwatt range).

Although the power needed for functions like displays, indicators, and remote control receivers is only in the milliwatt range, power supplies that are used to convert the AC line voltage to the low voltage needed to perform the functions typically operate at very low efficiency when they are operating at low power. As a result, the power consumed from the mains is often in the range of 1 W to 10 W or more, even when only a few tens of mW or less are needed.

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  Standby Indicator
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  Power supply
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  Temperature display

Although not considered a true phantom load, desktop computers left on will draw around 150W continuously. A laptop generally uses less than 50W, usually around 20W average.

Consequences of standby power

The ever increasing awareness of global warming has thrust energy efficiency to the forefront of public opinion. The wasted standby power of household electronic devices is typically very small, but the sum of all such devices within the household becomes significant. Standby power makes up a portion of homes' steadily rising miscellaneous electric load, which also includes small appliances, security systems, and other small power draws.

Standby power is typically 10 to 15 watts per device, and occasionally more.

For any single appliance the load is never very large (the most inefficient designs draw 15-20 watts), however when factored over all of the appliances in a country like the U.S. the load can come to billions of watts. Some studies have suggested that the total phantom load caused by the United States alone would provide enough power to handle the electric needs of Vietnam, Peru, and Greece.

Alan Meier, a staff scientist at the Lawrence Berkeley National Laboratory (LBNL) in Berkeley, noted that many household appliances are never fully switched off, but spend most of the time in a standby mode. His 1998 study estimated that standby power consumption accounted for approximately 5% of total residential electricity consumption in America, “adding up to more than $3 billion in annual energy costs”. According to America's Department of Energy, national residential electricity consumption in 2004 was 1.29 billion megawatt hours (MWh)—5% of which is 64m MWh. The wasted energy, in other words, is equivalent to the output of 18 typical power stations. His 2000 study showed that standby power accounted for around 10% of household power-consumption.

A similar study in France in 2000 found that standby power accounted for 7% of total residential consumption. Further studies have since come to similar conclusions in other developed countries, including the Netherlands, Australia and Japan. Some estimates put the proportion of consumption due to standby power as high as 13%.

From the US department of Energy:

"Many appliances continue to draw a small amount of power when they are switched off. These "phantom" loads occur in most appliances that use electricity, such as VCRs, televisions, stereos, computers, and kitchen appliances. In the average home, 75% of the electricity used to power home electronics is consumed while the products are turned off. This can be avoided by unplugging the appliance or using a power strip and using the switch on the power strip to cut all power to the appliance."

A careful analysis of the energy cost would also account for the effects of standby power on heating and cooling. During warm periods, more energy will be consumed for cooling. During cool periods, the heat generated by devices on standby may slightly reduce the need to heat a building by other methods. But electric heat is generally less energy efficient than other forms of heating. The net effect on energy efficiency however depends on the climate and heating and cooling methods used.

Fire risks

The subject of fire risk due to leaving a device in standby mode is a popular debate. There are reported cases where televisions have caught on fire in stand-by mode. The contributing factors for such fires include:

• Humid environments
• Lightning storms
• Age of the appliance

Modern televisions use only a small fraction of the power in standby mode (typically less than 10W). A modern HD LCD television will use only 1W or less when in standby mode (compared to 80-125W during standard operation). However, the risks of serious fire damage are increased since many people leave them in standby mode continuously when not in use, and when they are not at home. The risk of major fire damage originating from televisions left in standby mode is probably far below that for fires caused by other household appliances in regular use, such as ovens and refrigerators.

Policy

Further information: One Watt Initiative

In July 2001, U.S. President George W. Bush signed an Executive Order directing federal agencies to "purchase products that use no more than one watt in their standby power consuming mode".

In July 2006 The British Government announced it would outlaw televisions and video players that exceed the maximum standby-mode power consumption standard (1 watt). It was found that standby modes on electronic devices account for 8% of all British domestic power consumption.

Methods of reducing standby power consumption

To find out how much energy is used by standby power, a power meter can often be borrowed from the local power authorities[1] or a local public library[2][3].

There are a few simple methods to reduce standby power. The easiest way to do that is to simply unplug the unused devices. To switch off several devices that are often used together such as a PC, a monitor and a printer it is advisable to use a switchable power bar or surge protector with multiple sockets. Another alternative is to consider buying energy saving devices or devices that offer a real off switch. Replacing battery powered devices, such as cordless phones or rechargeable razors with corded alternatives not only cuts down on the standby power required to charge the battery, but also reduces energy lost in battery charging and discharging inefficiencies.

Switching devices on or off can be automated. Timers can be used to turn off standby power to devices that are unused on a regular schedule. Switches can turn the power off when the connected device goes into standby (e.g. Standby Plug[4]), or that turn on/off other outlets when a device is turned on or off are also available (e.g. USB Eco Powerstrip[5], Mini Power Minder[6], SmartStrip[7], IntelliPanel[8]). Switches can turn on/off based on activity sensors (e.g., Wattstopper[9]). Home automation sensors, switches and controllers can be used to handle more complex sensing and switching. However, many of these devices in their turn require standby power, as well as requiring energy and resources to make and recycle the device, so care should be taken to assure reduction in power use.

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  switchable multiple socket
• a socket which automatically switches off when it detects a device has gone into standby
  a socket which automatically switches off when it detects a device has gone into standby
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Some devices that use standby power may not turn on when power is removed and then reapplied by means of an external switch. A capacitor connected in parallel with the power switch can act as a momentary contact switch to turn on such devices when power is applied.

Some computers allow reducing of standby power by turning off components that use power when in standby mode. For instance, disabling Wake on LAN, wake on modem, wake on keyboard or USB may reduce power when in standby. It may be possible to disable such features that you do not use in the computer's BIOS setup.

Phantom load

The earliest known use of the term Phantom load was in "It's Gotta Be Spring" by Brian Green (N6HWY)on page 25 of Home Power magazine[10] #11, the June/July 1989 issue.

Many domestic appliances consume power when they are nominally off. Stereos, VCRs and television sets are examples. The phantom load can be caused by miniature transformers (such as wall warts) that convert AC electricity into DC electricity. The conversion is most efficient with large power draws, such as refrigerators, and least efficient with device that require little power, such as digital clocks. Phantom load is also caused by devices which feature small LEDs or other indicators that they still have power; these indicators obviously use power themselves.

Chasing phantoms

Finding phantom loads is not always easy. "Gas" stoves that use an electric clock constitute a phantom load. Recommended methods for finding phantom loads include turning off all lights at night and looking for any LEDs or other glows in the house. Any device that requires resetting after a blackout or power surge is a cause of phantom load. "Instant on" features are often an indicator of phantom load.

A simple test using a 'true power meter' or energy meter found that an all-in-one hi-fi unit (CD, tuner, tape deck) consumed 20W when 'off' and 60W when on but silent. Similarly, a recent microwave oven with a clock used 15W when not cooking (A similar model with a mechanical timer used no measurable power when not in use). It was found that recent models generally used more power in standby than devices from 5 years ago! A well designed study done by the American magazine Home Power magazine [11] found the average American household supports 1.45 kilowatt hours of phantom loads per day.[12]

References

• Pulling the plug on standby power, Mar 9th 2006, The Economist
• Executive Order - Energy Efficient Standby Power Devices, July 2001, The White House
• “Phantom Loads”
• “Is a Phantom Stealing Your Electricity?”

See also

• Green computing
• Low-power electronics
• Miscellaneous electric load

External links

• Standby Power Home Page, Lawrence Berkeley National Laboratory
• Official Energy Star Website, Energy Star
• International Conference on Standby Power, New Delhi INDIA