How much does standby power cost?
A small load can accumulate energy when it remains connected for long periods. Measure the actual low-power mode and count only the hours spent in that mode before estimating a yearly cost.
By HomeCost Radar · Reviewed 2026-09-27 · Editorial policy
Illustrative loads in standby for 20 hours a day
The 1 W, 5 W and 10 W values below are hypothetical measured averages, not typical ratings for any named product. Annual cost uses 365 days and an illustrative $0.20/kWh.
| Average standby power | Annual energy | Annual cost |
|---|---|---|
| 1 W | 1 / 1,000 × 20 × 365 = 7.3 kWh | $1.46 |
| 5 W | 5 / 1,000 × 20 × 365 = 36.5 kWh | $7.30 |
| 10 W | 10 / 1,000 × 20 × 365 = 73 kWh | $14.60 |
What the example shows: Reducing the assumed standby draw from 10 W to 1 W saves 65.7 kWh, worth $13.14 per year at the example price. A household total needs a separate measurement or assumption for each device.
Identify off, sleep and network-ready states
An appliance can appear off while using energy for controls or other functions. DOE's standby guidance distinguishes low-power modes and describes measuring a stable draw or averaging energy over time when it fluctuates.
Write down the selected mode alongside the reading. A device that is updating, charging a battery or recording content may not represent the quiet low-power state you intended to measure. Do not generalize a brief active reading to the whole night.
Make the time budget add up
If active use occupies four hours and standby occupies twenty, the total is twenty-four hours. Do not price twenty-four standby hours and then add four active hours for the same device; that counts four hours twice.
For a hypothetical device drawing 60 W during four active hours and 5 W for twenty standby hours, daily energy is 0.240 + 0.100 = 0.340 kWh. Standby accounts for 0.100 kWh of that modeled total, not an additional full day of consumption.
Evaluate changes against the measured saving
At $0.20/kWh, eliminating a continuous 1 W load for a 365-day year saves $1.75 before rounding differences. Compare that scale with the cost and power consumption of any additional switching device.
Preserve functions you need, such as networking, scheduled tasks or appliance controls. Do not disconnect equipment whose instructions require continuous power. This budget helps identify loads to investigate; it does not prescribe disconnecting every plugged-in device.
Frequently asked questions
Does a zero reading prove there is no standby energy?
Can I add all power-adapter ratings for a household total?
Sources and assumptions
The worked examples are HomeCost Radar calculations from the stated inputs. Sources below support the concepts identified beside each link; they do not certify our assumed wattages or product savings.
- DOE: measuring standby power — Low-power modes and averaging energy measurements when draw fluctuates.