Standby Power Cost Calculator

See how much a device costs per year just by being plugged in — in watts, kWh and reais.

How to use

  1. Type the standby power in watts — check the device label or measure with a plug meter.
  2. Set the hours per day the device stays in standby (24 if it is never turned off at the wall).
  3. Enter your electricity rate in R$/kWh (from your utility bill) and click Calculate.

About this tool

Standby power — sometimes called phantom load or vampire draw — is the electricity a device consumes while plugged in but not actively in use. A TV on standby might draw 1-5 watts, a game console 10-15 watts, a charger without a phone 0.1-0.5 watts. Individually small, but a house with twenty devices adds up.

This calculator multiplies the standby wattage by the hours per day and the rate per kWh to give you the annual cost. A 5-watt device running 24/7 at R$ 0.85/kWh costs about R$ 37/year — not dramatic, but multiply that by every device in the house and the number gets attention.

The practical takeaway: unplug what you can, use a power strip with a switch for clusters of devices (TV + sound bar + streaming box), and do not bother with chargers that draw under half a watt — the savings do not justify the inconvenience.

The formula

Annual cost = watts × hours/day × 365 / 1000 × rate (R$/kWh).

Frequently asked questions

How do I find the standby wattage?

The most reliable way is a plug-in power meter. Failing that, the manufacturer spec sheet lists typical standby consumption.

Is it worth unplugging everything?

For devices above 5 watts in standby, yes. For phone chargers below 0.5 watts, the annual cost is under R$ 4 — not worth the daily hassle.

Does this include the device when it is in use?

No — this is only the standby consumption. Active use draws much more.

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