Last updated: 2026-07-02

What Phantom Load Costs You

Every device that stays plugged in keeps drawing a little power even when it is switched off. This standby draw — phantom load, vampire power, idle current — is invisible on any single device, but running 24 hours a day, 365 days a year, it quietly adds up on the bill. Across a typical home it commonly accounts for 5–10% of total electricity use. This calculator turns a standby wattage into the concrete annual energy, cost, and CO₂ it represents.

How It Works

Standby power runs continuously, so the energy is just power times the hours in a year. There are 8,760 hours in a year, so:

where $P$ is the total standby power in watts, $n$ is the number of devices, $r$ is the electricity rate per kilowatt-hour, and $M$ is the CO₂ in kilograms. Dividing by 1,000 converts watt-hours to kilowatt-hours. The factor 0.4 kg CO₂ per kWh is a round global grid-average carbon intensity.

Worked Example

Suppose an entertainment centre — TV, sound bar, game console, and streaming box — idles at a combined 50 W, entered as a single device, on a rate of 0.15 per kWh.

First the annual energy:

Then the cost, at 0.15 per kWh:

And the emissions:

So that one cluster of devices burns 438 kWh, costs about 65.70 a year, and emits roughly 175 kg of CO₂ — all for electricity that does no useful work. On a switchable smart strip, cutting them fully off overnight and while away can recover most of that.

Common Standby Offenders

Older equipment and always-listening or instant-on modes are the worst culprits. Devices meeting the international 1-watt standby standard are far kinder, so replacing an old set-top box or console often pays back on standby savings alone.

Cutting the Load

The simplest fix is a switchable or smart power strip: group the TV, console, and sound bar onto one strip and kill them all with a single switch. Unplug chargers when they are not charging, turn off "instant-on" or "quick start" settings, and favour ENERGY STAR or low-standby models when buying new. None of this costs anything to run, and it trims both the bill and the carbon at once.

Measuring Accurately

Nameplate ratings and rules of thumb are only estimates. A plug-in energy meter (a "kill-a-watt" style device) placed between the wall and a device shows its real standby draw in watts, which you can enter here directly. Measuring a whole power strip at once gives the combined standby figure for everything on it.