Standby Power Calculator
Find the cost and CO₂ of devices left on standby.
Results update as you type.
How it works
Many electronic devices keep drawing power even when switched off or in standby, a hidden drain often called phantom load or vampire power, and this calculator reveals what it costs you in money, energy, and carbon over a year. You enter how many such devices you have, the standby wattage of each, how many hours a day they sit plugged in, and your electricity rate, and it returns the annual kilowatt-hours consumed, the yearly cost, and the estimated carbon dioxide emissions. Chargers left in sockets, televisions and consoles in standby, microwaves and coffee makers with clocks, set-top boxes, and computer peripherals all sip small amounts of power around the clock, and across a whole home these add up to a meaningful share of the electricity bill, commonly around five to ten percent. Seeing the yearly figure often motivates simple fixes: unplugging rarely used devices, grouping electronics on switchable power strips, and choosing energy-efficient models. The calculator uses 365 days and a typical grid emission factor to translate watts into real-world impact. It is a great tool for anyone trying to cut energy waste, lower bills, or reduce their carbon footprint. Enter your device count, standby watts, daily hours, and electricity rate to see the annual toll.
annual kWh = devices × watts × hours/day × 365 / 1000
Standby power draw is a wattage that runs continuously, so the yearly energy is the number of devices times the standby watts each, times the hours per day they stay plugged in, times 365 days, divided by 1000 to convert watt-hours to kilowatt-hours. Multiplying that energy by your electricity rate gives the annual cost, and multiplying by an average grid emission factor of about 0.4 kilograms of CO₂ per kilowatt-hour estimates the yearly carbon footprint.
Source:Standby power consumption and grid emission factor
We review all our tools from time to time to ensure accuracy.
Worked example
How to use this calculator
- 1
Enter your values
Enter number of devices, standby watts each and electricity rate.
- 2
Adjust the options
Adjust hours on standby/day if they apply — sensible defaults are already set.
- 3
Read your result
Annual energy updates instantly as you type — no button to press.
Frequently asked questions
What is standby or phantom power?
Standby power, also called phantom load or vampire power, is the electricity devices consume while switched off or in standby mode rather than actively in use. Clocks, remote-control receivers, indicator lights, and instant-on features all keep drawing small amounts of power continuously. Individually tiny, these draws run every hour of every day and add up to a surprising amount over a year across many devices.
How much does standby power cost?
Standby power commonly accounts for around five to ten percent of a household's electricity bill. The exact cost depends on how many devices you have, their standby wattage, and your electricity rate. Ten devices drawing five watts each around the clock use several hundred kilowatt-hours a year, which can be tens of dollars. The calculator gives your specific yearly figure from your inputs.
How can I reduce standby power?
Unplug devices you rarely use, and group electronics like TVs, consoles, and computer peripherals onto switchable power strips you can turn off with one click. Choose energy-efficient models with low standby draw, and enable power-saving settings. Smart plugs can cut power on a schedule. These simple steps eliminate much of the phantom load without affecting how you use the devices.
Which devices use the most standby power?
Older set-top boxes and cable or satellite receivers are notorious for high standby draw, sometimes over ten watts. Game consoles in instant-on mode, sound systems, older televisions, and always-connected smart devices also consume more than average. Simple chargers and small appliances draw less individually but are numerous. Measuring or estimating each device's standby watts helps you target the biggest offenders.
How is the CO₂ figure estimated?
The calculator multiplies the annual energy in kilowatt-hours by an average grid emission factor of about 0.4 kilograms of carbon dioxide per kilowatt-hour, a typical mix of generation sources. Your actual emissions depend on how your local electricity is produced; a grid rich in renewables emits less, while one reliant on coal emits more. The result is a reasonable estimate of the carbon impact of standby power.