Phantom Load Cost Calculator
Devices left plugged in keep drawing a trickle of power even when switched off or in standby. Because that draw runs every hour of the year, a few watts can quietly add real cost to your bill. This calculator turns a device's standby wattage into yearly energy use and running cost, using your electricity rate, and lets you scale it by the number of similar devices. Measure standby wattage with a plug-in meter for the most accurate result; every value here is a user-editable input.
Phantom load formula
kWh/year per device = watts * 24 * 365 / 1,000
Cost/year per device = kWh/year * rate
Total kWh/year = kWh/year per device * devices
Total cost/year = cost/year per device * devices
The 24 times 365 factor assumes the device is plugged in and drawing standby power all year. If you unplug it part of the year, scale the hours accordingly.
Cutting standby power
- Switchable power strips let you cut several devices with one switch.
- Network-connected and instant-on devices often draw the most standby power.
- Chargers left plugged in with nothing attached still draw a small load.
- Measure with a plug-in meter rather than guessing the standby wattage.
Phantom load: frequently asked questions
What is phantom load?
Phantom load, also called standby or vampire power, is the electricity devices draw while switched off or in standby but still plugged in: chargers, TVs, set-top boxes, game consoles and the like. It runs 24 hours a day, so even a few watts adds up over a year. This calculator turns standby wattage into yearly energy and cost.
How do I find a device's standby wattage?
Use a plug-in power meter to measure idle draw, or check the device's specifications. The US Department of Energy notes that standby power across a home's devices can add a meaningful share to the electricity bill. Standby wattage is a user-editable input here.
How is the yearly cost calculated?
Standby watts times 24 hours times 365 days gives watt-hours per year; divide by 1,000 for kilowatt-hours, then multiply by your electricity rate. This calculator does that for a single device's wattage and lets you scale it by the number of similar devices.
How can I cut phantom load?
Unplug devices not in use, use switchable power strips to cut several at once, and choose equipment with low standby draw. Devices with clocks, network connections or instant-on features tend to draw the most.
Official sources
- U.S. Department of Energy: Reducing standby power loads.
- U.S. Energy Information Administration: Electricity prices.
Reviewed by the CalculatorHub team, edited by James Graham, 19 June 2026. See our methodology.