How the cost of a device is worked out
Every device has two numbers that matter: the power it draws while it works, in watts, and how many hours it works. Watts times hours, divided by 1,000, gives kilowatt-hours (kWh) — the unit on your bill. Multiply by your price per kWh and you have the cost.
Most calculators stop there. We also count the hours a device is not in use but still plugged in. A TV, a games console or a set-top box draws a few watts in standby, 24 hours a day, every day of the year. On some devices that quiet draw is a large part of the yearly cost.
Standby: the bill for doing nothing
Lawrence Berkeley National Laboratory measured standby power in homes and found it is typically 5–10% of a household’s electricity. The usual culprits are set-top boxes and receivers, games consoles left in “instant-on” or rest mode, computers that sleep instead of switching off, and the small chargers and clocks that are always plugged in.
Switch to the “Standby audit of the home” tab, add what stays plugged in, and the calculator adds up what all of it costs you a year.
How to cut it
Measure first: a smart plug with energy metering shows what a device really draws, in standby too. Then let it switch the standby off — on a schedule, at night, or when you leave home. On the biggest standby sources it pays for itself within months; on a phone charger it never will, and the calculator says so.
Other cheap fixes: turn off “instant-on” or “quick start” in TV and console settings, set computers to sleep sooner, and put the TV, soundbar and console on one switched strip.
Questions
How do I calculate the electricity cost of an appliance?
Multiply its power in watts by the hours it runs a day, divide by 1,000 to get kWh a day, and multiply by your price per kWh. For a year, multiply by 365. Add the standby watts for the hours it is plugged in but off.
Does a device use electricity when it is switched off?
Many do, when “off” means standby: they keep a clock, a network connection or a fast start ready. Usually 0.5 to 5 W, more for set-top boxes and consoles in rest mode. Only unplugging or a switched socket brings it to zero.
What is phantom load?
Another name for standby power: electricity drawn by devices that are not in use. Berkeley Lab puts it at 5–10% of a typical home’s use.
Where do your power numbers come from?
From ENERGY STAR and US Department of Energy tables, Lawrence Berkeley National Laboratory standby measurements and EU energy-label data, all listed under Sources at the end of this page. Your own device may differ: the label on its back or a metering plug gives the exact figure, and you can type it in.
Which electricity price do you use?
The average household price, taxes included, in each edition’s market, from the national statistics office or regulator named in the sources. Change it to your own tariff in the calculator.
Other devices
Sources: US EIA, Electric Power Monthly: average residential price, August 2026 · Lawrence Berkeley National Laboratory: standby power · ENERGY STAR product specifications · US Department of Energy: estimating appliance energy use · EU product database for energy labels (EPREL) · EU Regulation 2023/826: standby and off-mode power · Our World in Data / Ember: carbon intensity of electricity, 2025 · Updated 2026-11