Measuring Standby Power

Standby Power Measurement Firms

Test labs that currently provide standby power measurement include:

FEMP encourages independent testing labs that provide standby measuring services to submit their information.

The International Electrotechnical Commission (IEC) 62301 test procedure describes a method for testing standby power use in appliances. The summary below introduces the general approach. However, consult the official document before undertaking the test.


The IEC 62301 test applies to all devices plugged into the electric mains by the end user. It is designed to measure the energy consumption of devices while in standby and other low-power modes.


Standby power consumption is defined as the lowest power consumption while plugged into the mains power supply. Other defined terms include standby mode, rated power, voltage, and frequency.

Testing Conditions

IEC 62301 defines testing conditions. The ambient temperature should be 23°C (+/- 5) with still air. The harmonic content of the supplied power should not exceed 2% up to and including the 13th harmonic and the ratio of peak value to r.m.s. value of the test voltage (sometimes called the crest factor) should be between 1.34 and 1.49.

The accuracy of the measuring equipment is also defined, but depends on the amount of power being measured. Measurements above 0.5 watts must be made with an uncertainty of less than to 2% at the 95% confidence level.

The power measurement instrument must be able to resolve:

  • 0.01 watts or less for power measurements below 10 watts
  • 0.1 watts or less for power measurements above 10 watts (up to 100 watts)

Portable Appliances

IEC 62301 defines a portable appliance as intended to operate on rechargeable batteries when not connected to a power source. For portable devices, the standby mode is measured on the charger or docking/base station with the appliance detached.

Measurement Procedure

If power consumption is stable (defined as less than 5% variation from the mean over an interval of 5 minutes), then the power consumption can be read directly from the meter. If power consumption fluctuates, then energy consumption should be measured over a period of time and then divided by the measurement period to determine average power.

IEC 62301 also lists information to be reported when making a measurement.