Standby Power Cost: Is Switching a Device Off Worth It?
Small standby loads add up over time, but the savings depend on the measured watts and the hours you can actually avoid. Calculate the possible saving before buying equipment to control it.
Calculate only the hours you can avoid
Annual saving = avoided watts ÷ 1,000 × avoided hours per day × 365 × price per kWh
For a 5 W standby load over 20 hours, daily avoidable energy is 0.1 kWh. At 18¢/kWh, that is $0.018 a day and $6.57 a year. Using 24 hours instead would overstate this particular opportunity because the device is needed for the other 4 hours.
The 5 W is an example, not a claim about your equipment. Measure the device in its actual standby state, with a meter suited to small loads.
A group can matter more than one device
Five devices each drawing 5 W in standby total 25 W. If all five can genuinely avoid those 20 hours, the group saves 0.5 kWh a day, or $32.85 a year at the example rate.
Record each device’s watts and unused hours separately when their schedules differ. Do not assume every device on a strip is available to turn off just because one is unused.
Account for the controller itself
Suppose a smart plug costs $20 and adds an average 1 W of continuous consumption. That hypothetical controller uses 8.76 kWh, costing $1.58 a year at 18¢/kWh.
If it eliminates only the single 5 W standby load above, the net saving is about $4.99 a year. The simple purchase payback is about 4 years, before other costs. These are illustrative inputs, not tested smart-plug specifications.
A manual control has a different trade-off: it may avoid a purchase and controller load, but savings depend on actually using it. Compare the complete arrangement that you would live with.
Confirm what must stay powered
Standby can support useful functions such as remote access, recording, updates, or wake-up features. Decide which functions you need before changing a schedule. Equipment that provides essential monitoring or protection is not a candidate merely because its energy use looks small.
Use switching equipment within its manufacturer’s voltage and load limits. Follow the device’s shutdown instructions; do not treat disconnecting power as a substitute for a required shutdown process.
Make a useful before-and-after comparison
Measure a normal period before the change and a comparable period after it. Record any different usage. The difference in kWh, multiplied by your variable rate, is the energy-cost change for those periods.
For a quick estimate in the calculator, use the avoided watts as the active watts, set active and total hours to the hours avoided, and set idle watts to zero. Label the entry “potential standby saving” so it is not confused with your current total.
Sources and calculation notes
Worked examples are Always On Cost calculations using the stated assumptions, not product tests or utility quotes. Unless noted otherwise, estimates use a fixed rate and repeating daily schedule, with 365 days per year. USD amounts are rounded for display.