Cutting standby power
with a smart plug
can cost you more.
The short version…
- The plug itself uses power. About 1 W = about ¥272 a year
- Switching off a device on 1 W or less of standby won't pay for itself
- The real value is measuring. Never plug in a heater
Save or lose? Standby power calculator
Choose your device's standby power (待機時消費電力 in the spec section of the manual) and how long the smart plug keeps it switched off. We subtract the power the plug itself uses.
365 days a year at ¥31/kWh. The plug uses its "OFF" power while the device is switched off and its "ON" power the rest of the time. For SwitchBot we used "about 1 W" (official support page) for both.
Turn your readings into yen
Enter the daily energy (kWh) shown in your smart plug's app to get the cost per month and per year — the cost of how you actually use it at home, not a catalog figure.
If the app shows Wh, divide by 1,000 (300 Wh = 0.3 kWh). At ¥31/kWh — your rate depends on your contract.
Our picks by type
- Exports power-use records
- Bluetooth and Wi-Fi
- Rated 1,500 W with overload protection
- Enter your electricity rate for a monthly estimate
- Works with Matter (Alexa, Google, Apple)
- Turns off when power goes over a limit you set
* Products and prices load from Rakuten Ichiba when you open the page.
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What to plug in — and what not to
All a smart plug does is plug and unplug the device for you. So it suits devices that start working as soon as they get power and don't mind being cut off suddenly.
○ Good to plug in
- Floor lamps and accent lights
- Circulators and fans (push-button types that run when plugged in)
- Phone chargers (some plugs can cut power when the draw drops below a level)
- Anything you just want to measure
× Never plug in
- Heaters: electric stoves, kotatsu, electric blankets, heated carpets (see "Why heaters must not be plugged in")
- Kettles, coffee makers, hair irons — anything that makes heat
- Air conditioners and other devices that must not be unplugged while running
- PCs and other devices that need a shut-down process
Why heaters must not be plugged in
It's tempting to warm up the kotatsu before you get home, but smart plug manuals forbid connecting heaters. Meross's MSS110 manual, for example, says Japan's Electrical Appliances and Materials Safety Act prohibits remotely operating electric heaters and electric stoves through the plug. LinkJapan's ePlug3 also says electric stoves, heaters, kotatsu and electric blankets can't be connected.
Electric stove fires start when laundry or bedding touches the heater (NITE). If it turns on in an empty room, nobody notices something has fallen near it.
NITE confirmed cases of electric heaters switched on by other appliances' remote controls, such as a TV's, and the technical standard for electric heaters was revised as a result (NITE Alert No.83). A mistake in an app or schedule can do the same.
How much is standby power?
A survey by Japan's Agency for Natural Resources and Energy (FY2012) found standby power was 228 kWh a year per household, about 5.1% of home electricity use — about ¥7,068 at ¥31/kWh. That's down from 285 kWh in the FY2008 survey.
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The biggest standby users are gas water heaters (19%), TVs (10%), heat-pump air conditioners (8%), phones (8%) and video recorders (6%). The survey also notes that unplugging can be inconvenient and, for some devices, a safety or durability issue. Phones and routers are a pain to unplug.
5 things to check when buying
-
It measures power
Measuring is what helps you save. The SwitchBot Plug Mini records and exports power use; the Tapo P110M shows a monthly cost estimate once you enter your rate. Some cheap smart plugs can't measure, so look for 電力モニター (power monitor) in the listing. -
Rated 1,500 W / 15 A, with overload protection
Both the SwitchBot Plug Mini and the Tapo P110M handle up to 1,500 W / 15 A. Don't let devices on a power strip add up to more. SwitchBot cuts power before your breaker trips if the load passes 15 A. -
It fits your outlet
The SwitchBot Plug Mini has a polarized plug (one blade wider). It needs an outlet with one longer slot (N-pole type) or a polarized extension cord. -
2.4 GHz Wi-Fi
Both work only with 2.4 GHz Wi-Fi, not your router's 5 GHz band. -
The smart speaker or apps you use
The Tapo P110M supports Matter, so you can control it from Alexa, Google Assistant or Apple Home (Matter needs each platform's hub). SwitchBot pairs easily with its own sensors and curtain robots.
Good to know if you live in Japan
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Search in Japanese
Smart plug is スマートプラグ. Power monitoring is 電力モニター or 消費電力モニタリング. Standby power is 待機電力; a switched power strip is 節電タップ. -
Buy a model made for Japan
Household power here is 100V, and outlets take two flat blades. A model sold in Japan lists Japanese certifications — LinkJapan's ePlug3, for example, shows the PSE mark (electrical safety) and Japan's radio technical conformity mark (技適, the "R" mark). -
Your electricity rate
This page uses ¥31/kWh. Your real rate is on your bill (電気料金のお知らせ) — enter it in the plug's app for a closer estimate.
Preventing outlet fires
Do: keep the total within what the strip or smart plug says (e.g. "up to 1500W"). Bundled cords trap heat and can catch fire (NITE)
Do: dust and moisture between the blades can spark a fire ("tracking"). Unplug off-season devices and wipe dust off with a dry cloth (NITE)
FAQ
Can a smart plug save standby power?
Can I turn on a kotatsu or electric blanket with a smart plug?
How much does the smart plug itself cost to run?
Smart plug or switched power strip?
How do I measure a heater's running cost?
Which heater is right for you?
Answer 6 questions and find the heater that's just right for you.