How to Use This Tool
Scale a measured low-power mode across devices, hours, days and your own electricity price. Calculate annual and monthly standby energy, daily watt-hours and cost using measured watts and an editable electricity price.
The decision this tool supports
A few watts look negligible until multiplied across always-plugged devices and a full year. This page keeps the decision bounded to annual standby cost and the supporting outputs shown beside it. Standby Power Cost does not import an account, infer a market rate, or silently substitute an industry average.
Inputs and units
The Standby Power Cost calculation uses Measured standby power per device, Number of devices, Standby hours per day, Days per year, Electricity price. Keep all money values in one currency and all time, distance, mass, energy or volume entries in the unit printed beside the field. Mixing Standby Power Cost scopes can produce a plausible number with the wrong meaning.
- Measured standby power per device is entered in W.
- Number of devices is entered in devices.
- Standby hours per day is entered in hours.
- Days per year is entered in days.
- Electricity price is entered in currency/kWh.
Formula and worked check
Annual kWh = standby watts × device count × standby hours/day × days/year ÷ 1,000; cost multiplies by the entered price. Eight devices drawing 5 W for 24 hours across 365 days use 350.40 kWh and cost $63.07 at $0.18/kWh. The Standby Power Cost default is an executable known-answer case, not a benchmark or recommendation. Change one input and verify that the direction of annual standby cost still matches the stated relationship.
How to interpret the result
Compare annual cost with the convenience and safety of switching equipment off; do not disconnect devices that require standby for protection or service. The additional Standby Power Cost outputs expose the denominator, comparison, capacity or reverse value needed to audit the primary result instead of presenting one unexplained number.
Assumptions
- Standby watts are measured in the relevant low-power mode.
- Hours per day do not exceed 24.
- Electricity price is user entered and includes only intended charges.
Save the Standby Power Cost input values and date with any material decision. A later Standby Power Cost rerun is reproducible only when the same assumptions and units are available.
Limitations and safety boundary
Nameplate power may not equal measured standby power, and time-of-use prices, cycling states, power strips and seasonal use are excluded. Standby Power Cost is an estimate and cannot replace a contract, local code, licensed professional, calibrated measurement, lender statement or platform report where one governs the decision.
Source and privacy
The Standby Power Cost definition or rule was checked against U.S. Department of Energy — Measuring standby power on 2026-08-26. Recheck U.S. Department of Energy — Measuring standby power when a specification or policy behind Standby Power Cost can change. Standby Power Cost arithmetic runs in this browser tab; ecech does not receive the values through a calculation API.
Sources & assumptions
Tool Spec v2 · verified 2026-08-26. Platform rules and fees can change; the editable inputs remain authoritative for your account.
Official references
- U.S. Department of Energy — Measuring standby power (checked 2026-08-26)
Model assumptions
- Standby watts are measured in the relevant low-power mode.
- Hours per day do not exceed 24.
- Electricity price is user entered and includes only intended charges.
- Nameplate power may not equal measured standby power, and time-of-use prices, cycling states, power strips and seasonal use are excluded.
