Energy-saving Features and Standby Power
Some power strips have energy-saving features, which switch off the strip if appliances go into standby mode. Using a sensor circuit, they detect if the level of current flowing through the socket is in standby mode (less than 30 watts), and if so they will turn off that socket. This reduces the consumption of standby power used by computer peripherals and other equipment when not in use, saving money and energy. Some more-sophisticated power strips have a master and slave socket arrangement, and when the "master" socket detects standby mode in the attached appliance's current it turns off the whole strip.
However, there can be problems detecting standby power in appliances that use more power in standby mode (such as plasma televisions) as they will always appear to be switched on to the power strip. When using a master–slave power strip, one way to avoid such problems is to plug an appliance with a lower standby wattage (such as a DVD player) into the master socket, using it as the master control instead.
A different power strip design intended to save energy uses a passive infrared (PIR) or ultrasonic sound detector to determine if a person is nearby. If the sensors don't detect any motion for a preset period of time, it shuts off several outlets, while leaving one outlet on for devices that should not be powered off. These so-called "smart power strips" are intended to be installed in offices, to shut down equipment when the office is unoccupied.
It is recommended that appliances that need a controlled shutdown sequence (such as many ink-jet printers) not be plugged into a slave socket on such a strip as it can damage them if they are switched off incorrectly (for example the inkjet printer may not have capped the print head in time, and consequently the ink will dry and clog the print head.)
Within Europe, power strips with energy-saving features are within the scope of the Low Voltage Directive 2006/95/EC and the EMC Directive 2004/108/EC and require a CE mark.
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