Do Smart Plugs Use Electricity When Not in Use? (Standby Cost)
By Marlo Strydom · Updated
Yes. A smart plug sips a little power all day, even when the outlet it controls is off. The draw is tiny, but it never stops.
So the real question is whether the plug saves more than it uses. That depends on what you plug into it.
What Standby Use Means for Your Bill
- The plug has to stay awake to listen for commands, even when its outlet is off.
- ENERGY STAR limits qualifying smart plugs in home energy systems to 1 watt of standby power.
- Use your utility rate and the plug's measured watts to find the real yearly cost.
- Schedule a device only if its own standby draw is bigger than the plug's.
Why a Smart Plug Uses Power While Off
When you turn a smart plug "off," only its outlet turns off. A small switch inside, called a relay, cuts power to your device, but the plug's radio and control chip stay on to hear the next command. Some models also run a status light or energy meter.
Power used by a device that seems off is called standby power. It adds up across a home: Berkeley Lab's standby research puts it at 5 to 10 percent of home electricity use.
How to Calculate the Yearly Cost
Find the plug's standby watts in its specs, or measure it with a plug-in power meter. Multiply the watts by 8.76 to get kilowatt-hours (kWh) per year.
The 8.76 comes from the 8,760 hours in a year, divided by 1,000 because a kilowatt is 1,000 watts. Then multiply the kWh by the price your utility charges per kWh.
| Standby draw | Energy per year | Cost at $0.15 per kWh |
|---|---|---|
| 0.3 watts | 2.63 kWh | $0.39 |
| 0.5 watts | 4.38 kWh | $0.66 |
| 1.0 watt | 8.76 kWh | $1.31 |
| 1.5 watts | 13.14 kWh | $1.97 |
The table uses an example rate, not a national average. Swap in the rate from your own bill.
When a Smart Plug Saves More Than It Uses
Compare the plug's all-day draw with the power it cuts from your device. For example, a 1-watt plug uses 8.76 kWh per year.
Say it cuts off a device that draws 5 watts in standby for 12 hours a day. That avoids 21.9 kWh a year, so after the plug's own use, you save about 13.14 kWh.
Savings aren't automatic. A lamp that uses zero watts when switched off costs more with a smart plug, not less. A game console, TV, or sound system may save energy, but only a meter or the product specs can tell you how much.
Devices That Should Stay Powered
Never cut power to a refrigerator, medical device, security system, router, recorder, or anything that must stay online. Experts warn that a smart plug could switch off medical equipment by accident. A fridge needs steady power too, since the USDA says it keeps food safe for up to 4 hours once the power goes out.
Some electronics also need standby power for updates, recordings, clocks, or safe shutdowns. Check the manual before putting any device on a schedule. A smart fridge keeps cooling without Wi-Fi, but it still needs electricity.
Three Ways to Get a Useful Result
- Measure first: Record the device's off-state draw and the plug's own draw.
- Use a real schedule: Count only the hours when the device can safely be unplugged.
- Check the load rating: Keep the connected device within the smart plug's volt, amp, watt, and load-type limits.
