Measuring Power Consumption

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There are a few different ways to discover the power consumption of ICT products being considered for off-grid use. Manufacturers’ specifications are the first place to look. New equipment should come with information about the equipment’s power rating, the highest wattage that the device can safely tolerate. This information provides an upper bound to potential power consumption. Specifications, user’s guides and other documentation may provide more useful data on peak, average or normal power consumption in various states of operation. In the case of second-hand ICT equipment that lacks documentation, you may be able to contact the manufacturer or check the manufacturer’s web site for archived information on older products.

If there is an electricity meter installed on the premises, you may be able to determine the power consumption from the change in kWh recorded by the meter. This approach was used successfully by Winrock as part of the USAID-sponsored dot-ORG program in Rwanda to determine the power consumption of a grid-connected telecenter that needed a backup power system. In this case, the telecenter’s electricity was on a separate circuit and was metered independently, so that the power draw of individual devices could be determined by shutting off all devices but one, in turn. The power readings captured using this method were reasonably consistent with professional readings taken at a later date.

Measurement Tools

Another option is to measure the power draw of the equipment using a Watt meter or an ammeter. If you want to do it yourself and feel that your needs are significant enough to warrant purchasing a portable meter, this type of equipment typically costs from US$100 for a small Watt meter to several hundred dollars for more accurate and sophisticated devices.

The Watt meter should display the instantaneous power (Watts) consumed by the load as well as the total energy consumed over a period of time (kilowatt hours). When selecting a Watt meter, make sure that the device displays a sufficient number of decimal places to get a useful reading for your ICT device. If you will be measuring one device at a time, it is more convenient to have instantaneous readings delivered in Watts rather than kilowatts. For cumulative readings, kilowatt hours and hours should be reported with at least one decimal place (increments of 100 Watts hours and tenths of an hour, respectively).

If you don’t have a metering device and don’t wish to purchase one, a local electrician, technician, renewable energy installer or a local telecommunications company that already owns the necessary equipment may be able to take the measurements.

Taking Measurements

For devices with varying power consumption, it is best to calculate the average power consumption rate under actual usage conditions. For computers, the average power consumption under actual usage conditions will be greatly affected by the percentage of time that the computer is active, idle and in sleep mode.

If it is not possible to measure the average power consumption during actual usage, one alternative is to measure the power consumption of the ICT device in each operating state or mode and multiply by the expected number of hours of usage in each mode. For example, television sets will typically have an active mode and a standby mode, in which the set appears to be “off” but can be turned on by remote control. Power consumption may differ significantly in each mode. The table below lists operating modes that may be important to measure for certain ICT devices.

ICT Operating States to Measure

Operating States to Measure


  • Initial start-up power.
  • Active (displaying picture and sound).
  • Standby/Off (TV screen is off/blank but can be turned on by remote control).
Personal computer
  • Active power consumption. A quick way to produce active power consumption is to drag an open window on the screen in circles for a few seconds.
  • Idle power consumption. The computer is booted and active, but not running any programs or receiving user input through the keyboard or mouse.
  • Standby/sleep mode(s).
  • Off.
CRT monitor
  • Initial start-up power (typically 2-3 times higher than average power).
  • Active (displaying output from booted computer). The monitor should be tested while operating at the desired resolution level (i.e., 800x600 , 1024x768). As with CRT television sets, the power consumption can vary slightly with adjustments to brightness/contrast and sound volume.
  • Sleep/deep sleep modes.