Answer by
DrHarris (508)

Most DSL modems use between 6-9 Watts, which is between 4-6 Kilowatt Hours per month. To calculate your actual power usage, look for Amps and Voltage on your modem's power supply, and multiply them. This is the wattage per hour. Multiply Watts per Hour by 24 Hours and 30 Days, and this is your estimated kWh per month.