Phantom Load Calculator

How to use the phantom load calculator

Enter how many always-plugged devices you have, the average standby watts each one draws while it is nominally off, and your electricity rate, and you get the dollars those devices cost you a year just sitting there, plus the kilowatt-hours behind that number and the monthly figure. The point of the calculation is that standby runs around the clock. A device left on standby is assumed to draw its trickle 24 hours a day, 365 days a year — 8,760 hours — so even a couple of watts turns into a real line on the bill. That around-the-clock assumption is why one watt of standby is worth roughly the same over a year as a 60 W bulb burning three hours a night.

Start by counting the devices that never truly switch off. Walk a room at a time and tally anything that stays plugged in and warm to the touch, shows a clock or a standby light, or wakes the instant you press a button — televisions, set-top and DVR boxes, game consoles, the microwave and the coffee maker with their glowing clocks, and chargers left in the wall with nothing attached. The default of 10 devices is a fair count for one household, but most homes have more than people expect once they actually look. Lawrence Berkeley National Laboratory measured whole-house standby loads spanning 14 to 169 watts with an average of 67 watts, and named televisions, set-top boxes and printers as the largest single contributors.

Then estimate the average standby draw per device, and be aware how wide the spread is. Modern equipment designed to a modern standard sips a fraction of a watt: since 6 January 2013 the European Union has capped off-mode and standby at 0.5 watts, or 1 watt where a display is showing, under Regulation 1275/2008, which itself grew out of the International Energy Agency One Watt Initiative. Older and always-listening gear sits far higher. LBNL measured cable boxes, internet terminals and satellite receivers at 10 to 15 watts whether on or off, and set-top boxes generally at 20 to 25 watts in both active and standby mode. The default of 3 watts is a reasonable middle for a mixed bag, but a house full of set-top boxes deserves a much higher figure.

The rate is the input that varies most, so use your own. This tool defaults to 17.5 cents per kWh; the Energy Information Administration reported a US residential average of 18.11 cents per kWh year to date for 2026 and 18.44 cents in May 2026, with state figures scattered well above and below. Add the per-kWh supply and delivery line items together, or divide a full month total by the kilowatt-hours used, and enter that. Then read the result three ways: the annual cost is the headline, the kWh figure is the same thing free of any rate assumption, and the monthly figure scales it to bill-sized terms. Because standby is continuous, this is a steady every-year cost rather than a one-off.

The formula

Standby power is just watts that never turn off, turned into energy and then into money. Take the watts each device draws, turn them into kilowatts by dividing by 1,000, multiply by the number of devices and by every hour of the year — 24 hours across 365 days, which is 8,760 hours — to get the energy, then multiply by your rate to get the cost. There is no duty cycle and no runtime input, because the whole premise of standby is that there is no off.

That 8,760 is what separates this calculation from every other appliance sum on the site. Anywhere else, a small wattage is forgiven by short runtime; here nothing is forgiven. One watt held continuously for a year is 8.76 kWh, so at the US residential average of 18.11 cents per kWh that the Energy Information Administration published for 2026 year to date, a single watt of permanent standby costs about $1.59 a year. Multiply by the number of watts and the number of devices and the total follows.

hours in a year = 24 × 365 = 8,760
kWh per year = devices × (standby watts ÷ 1000) × 8760
annual cost = kWh per year × rate
cost of one permanent watt = 8.76 kWh × rate

Worked example with the defaults: 10 devices × (3 ÷ 1000 = 0.003 kW) × 8,760 hours = 262.8 kWh a year. At the default rate of $0.175 per kWh that is $45.99 a year, and dividing by twelve gives the $3.83 a month the tool shows. Scale it to a heavier setup and it bites harder — 20 devices at 5 W each is 876 kWh a year, about $153.30 at the same rate — and scale it down to modern gear meeting the 0.5 W European ceiling and 20 such devices come to 87.6 kWh, about $15.33. The spread between those two houses is a factor of ten.

The measured evidence is worth knowing, because it stops this being a rule of thumb. Lawrence Berkeley National Laboratory whole-house measurements found total standby loads ranging from 14 to 169 watts with an average of 67 watts, and identified televisions, set-top boxes and printers as the largest contributors. LBNL work on set-top boxes recorded 20 to 25 watts drawn in both active and standby mode, and 10 to 15 watts for typical cable boxes, internet terminals and satellite receivers whether switched on or off. A 67 watt house average works out to 587 kWh a year, which at 18.11 cents per kWh is about $106.29.

How large a share of the bill that represents depends entirely on what you own. Research by Alan Meier and colleagues at LBNL put leaking electricity at roughly 5 to 10 percent of residential electricity use in the United States, with bottom-up estimates spanning about 3 to 12 percent across countries. Treat that as a range rather than a figure, and let the calculator give you a number for your own house instead. The two practical levers are unplugging what you rarely use and putting clusters of electronics on a switched or smart power strip, so the gear that gains nothing from staying half-awake stops drawing at all while anything that genuinely needs standby keeps it.

Frequently asked questions