Operating cost
Standby Power Cost Calculator
Always-on boxes, clocks, and idle chargers draw a few watts all day. This page prices that idle draw. It is not a general appliance scheduler.
Numbers stay in this browser. EnergyToolMage does not upload your inputs or require an account.
Formula
kWh/year = standby_W × hours/day × 365.25 ÷ 1000; cost = kWh × USD/kWh
Assumptions
- Default hours/day is 24.
- Standby watts are constant.
- Example rate is illustrative.
How it works
Daily energy is standby watts × hours/day ÷ 1000. Yearly energy multiplies by 365.25.
Inputs and results
Inputs: standby W, optional hours/day, USD/kWh. Outputs: daily and yearly kWh and USD.
Worked examples
5 W idle, 24 hours, $0.16/kWh
0.12 kWh/day. 43.83 kWh/year. $7.01/year at the example rate.
How to use this calculator
- Enter standby watts (idle, not running).
- Keep 24 hours/day unless the device is unplugged part of the day.
- Enter your electricity rate.
- Read daily and yearly kWh and dollars.
Limitations
- Does not inventory every outlet in a house.
- Not a professional energy audit.
Sources and freshness
- Every rate, wattage, hour, and loss percentage is a user input or a labeled example. Nothing here is a live utility tariff.
- The $0.16/kWh figure that appears in examples is an illustrative default, not a U.S. average and not current.
- Annualization uses 365.25 days per year and 365.25 ÷ 12 days per month. Your billing cycle will differ.
Questions
How do I measure standby watts?
A plug-in power meter is the honest method. Nameplate watts are usually the running load, not standby.
Why default to 24 hours?
Vampire load is defined as the draw while the device is waiting. If it is unplugged part of the day, lower the hours.
Is this the same as the appliance calculator?
The math is the same identity. This page stays on idle watts and yearly vampire cost so the query family stays distinct.
Related energy tools
- Appliance costUse this when you know an appliance’s watts and how often you run it. The page annualizes with a disclosed calendar convention and your bill rate.
- Electricity costMultiply energy you already know in kilowatt-hours by the dollars-per-kWh on your bill. Use this when a meter, EnergyGuide label, or another calculator already gave you kWh.
- LED savingsEnter the existing wattage, the replacement wattage, hours per day, and your bill rate. The page prices the yearly energy difference. It is not a second appliance scheduler.