Home energy · Everyday energy
What does standby power cost a year?
Add the standby watts of the devices that stay plugged in and get the yearly kWh and cost of vampire loads.
Inputs
Starting values are illustrative, not current prices or specifications. Replace each with your own.
Result
Answer
Standby cost per year is watts × quantity × standby hours per day × 365 ÷ 1,000 × your price per kWh, added up across devices. The example devices total 153.3 kWh and $23.00 a year at 20 standby hours a day and $0.15 per kWh.
Worked example
Device 1: 5 W × 1 × 20 h × 365 ÷ 1,000 = 36.5 kWh. Device 2: 10 W × 1 = 73.0 kWh. Device 3: 3 W × 2 = 43.8 kWh. Total 153.3 kWh × $0.15 = $23.00 a year, $1.92 a month.
Formulas and notes
- Per device kWh a year = watts × quantity × hours on standby per day × 365 ÷ 1,000. Cost = kWh × price per kWh (DOE).
- DOE describes vampire loads as electricity wasted when electronics are not in use, and says an advanced power strip can reduce them. It also says a usage monitor measures any device that runs on 120 volts; monitors cost around $25 to $50 at most hardware stores.
- The starting watts are illustrations, not typical figures: measure your own devices.
Planning estimate only, not professional advice. Sources, checked 2026-10-08: U.S. Department of Energy, Estimating Appliance and Home Electronic Energy Use (archived copy, 2024-12-31) · U.S. Department of Energy, Reducing Electricity Use and Costs (archived copy, 2024-12-31)
FAQ
What is vampire power?
DOE describes vampire loads as electricity that is wasted when electronics are not in use.
How do I find a device's standby watts?
Plug it into a usage monitor. DOE says a monitor works on any 120 volt device and costs around $25 to $50 at most hardware stores.
How can I cut standby use?
DOE suggests an advanced power strip to reduce vampire loads. Unplugging devices you do not use also stops them.
How many hours should I enter?
The hours each day the devices are plugged in but not in use. Twenty is a starting guess.
Does this include devices that are always on, like a router?
You can enter them with 24 hours, since they draw power all day.