Purchasing guidelines for external power supplies and battery chargers
Most offices have many small appliances with separate power supplies. Taken individually these devices do not consume much power, but if there are many the amount of wasted power can be significant.
Purchasing requirements for external power supplies and battery chargers
Conform to Energy Star specifications effective from 1 January 2005 as amended per note 3 below.
| Equipment type. Maximum. Power output, watt | Active mode (1) Efficiency % | No-load (2) watt |
| 0 < power ≤ 1 | 49 x power | 0.50 |
| 1 < power < 10 | 9 x Ln(power) + 49 | 0.50 |
| 10 ≤ power ≤ 49 | 9 x Ln(power) + 49 | 0.75 |
| 49 < power ≤ 75 | 84 | 0.75 |
| 75 < power ≤ 250 (3) | 80 | 0.75 |
The requirements apply to external power supplies and battery chargers (supplied with appliance or separately) for normal use in offices and homes. Power consumption is the maximum permitted for energy efficient equipment, but efficiency is the minimum allowed.
Notes and additional definitions
(1) Average efficiency, which is the minimum allowed for energy efficient equipment. ‘Ln(Power)’ is the natural logarithm of efficiency, which is the maximum power output in watts.
(2) No device connected.
(3) Conforms to power factor correction per EN61000-3-2 standard. Adapted per Energy Star which does not have an equivalent correction, and where the requirement is therefore 84%.
Changes in relation to the 2007 specifications
There are no changes in relation to the 2007 specifications.
Good advice on purchasing and operating equipment
- Use an AutoPowerOff plug banks to automatically switch off cordless and mobile telephone chargers when the computer is switched off. Read more about AutoPowerOff plug banks.
- New Energy Star specifications are pending for external power supplies and battery chargers. Consider basing your purchases on the new requirements once they come into force. The new requirements will be available at www.savingtrust.dk
- Follow new Energy Star guidelines for power supplies and battery chargers published in 2008.
Page last updated 06.10.2008