What You Can Plug Into a Smart Plug From a Mystery Box
A smart plug is the quiet workhorse of a mystery box: a block between your socket and a lamp that lets your phone switch it. It is also a relay in a plastic shell with a current limit printed on it that you have probably never read. On a lamp you never think about that number; on a heater it is the whole story. Here is what you can put on it, and what you must not.
The Number on the Back
Turn the plug over and you will find a rating in amps and sometimes in watts: 10A, 15A, 16A, or a wattage such as 1200W or 1800W. That is the most current the relay inside is built to switch and carry for you. On a 120-volt North American socket, 10 amps is about 1,200 watts and 15 amps about 1,800; on a 230-volt European or Australian socket the same amps carry roughly twice the watts. Some plugs print two figures, a peak and a continuous, and the continuous one is the one that matters for anything you run longer than an hour. A plug with no rating printed anywhere is a plug whose limit you do not know, which is a reason to keep it on a lamp.
Whether the plug fits your wall at all, and why a 220-volt plug that slides into a 120-volt socket is a problem rather than a convenience, is in voltage and plug compatibility in a mystery box. The rest of this page assumes your plug matches your wall.
What Draws What
- Read the amp rating on the plug and keep any load that runs for hours under about 80 per cent of it; a 10A plug is comfortable at 1,000 watts and a 15A plug at 1,400.
- Lamps, fans, chargers, small kitchen gadgets and Christmas lights are fine; space heaters, air conditioners, kettles, irons and anything with a motor that starts under load are the ones that overheat a cheap plug.
- Never plug a power strip or an extension lead into a smart plug, and never chain smart plugs; the plug's limit applies to everything downstream of it at once.
| What you want to switch | Typical draw | On a 10A plug | On a 15A plug |
|---|---|---|---|
| Lamp with an LED bulb | 5 to 15 W | Fine | Fine |
| String lights, a tree, a light strip | 10 to 100 W | Fine | Fine |
| Phone chargers, a speaker, a router | 5 to 60 W | Fine | Fine |
| Desk fan, humidifier, diffuser | 20 to 60 W | Fine | Fine |
| Television, games console | 50 to 250 W | Fine | Fine |
| Slow cooker, coffee maker | 200 to 1,000 W | Borderline for hours | Fine |
| Space heater | 750 to 1,500 W | No | Only a plug rated for heaters, and not from a box |
| Kettle, toaster, iron, hair dryer | 1,000 to 1,800 W | No | No |
| Window air conditioner, refrigerator, pump | 500 to 1,500 W plus a starting surge | No | No |
| A power strip with anything on it | Unknown | Never | Never |
Read the heater row as the one that matters to you. A 1,500-watt heater draws about 12.5 amps on a 120-volt wall, which is inside a 15A plug's peak rating and outside the continuous rating most cheap plugs can actually sustain; the relay runs warm, the plastic softens, and the connection at the pins is where a cheap plug fails. Plugs sold specifically for heaters exist, with heavier relays and a safety listing to match; a plug from your random box is not one of them, whatever its label says. Read the motor rows for a different reason: a fridge or an air conditioner draws several times its running current for a moment when it starts, and that surge is what welds a small relay shut, so the plug stops switching off. The power strip row is the rule with no exceptions, because a strip lets you exceed your plug's limit without your knowing it.
Note: The plug is a mains device, and it is the one item in your box whose safety mark matters most, because it sits in your wall carrying whatever you hang on it. Look for UL or ETL in North America, CE and the relevant national marks in Europe, printed on the body and not only on the box. What those marks mean and how to check one is in UL, ETL and the charger in your mystery box. A plug with no mark belongs on a lamp or in your bin, not on anything that heats.
Using It Well
- Pair it on the 2.4GHz band, which is the step that stalls most people; the fix is in smart home gadgets from a mystery box: the 2.4GHz problem.
- Feel it after an hour with your intended load running. Warm is normal; too hot to hold comfortably means the load is too much for it.
- Use the schedule for lights and the timer for anything you might forget, such as a diffuser or a heated blanket's low setting, and not as a substitute for a thermostat on anything that heats.
- Check it still switches off now and then with a load on. A relay that has welded stays on, and the app will say off while the lamp stays lit.
- Plug it straight into the wall, not into an extension lead and not with one hanging off it.
Fault or Limit?
- It clicks and switches a lamp but not a heater. Some plugs cut out on overload; that is the plug protecting itself, and the heater is over its limit.
- It gets warm with a fan on it. Slightly warm is normal. Hot with your 40-watt fan is a fault.
- The app says off but the device stays on. A welded relay, usually after a motor or a heater. The plug is finished; do not use it again, and report it if it happened on a light load.
- It will not pair. Almost always your Wi-Fi band, not the plug.
- It smells of hot plastic, or the pins are discoloured. You stop using it now.
A plug that fails on a lamp, will not pair on a correct 2.4GHz network, or heats up with a light load is a fault to photograph and report inside the seller's window; the routine is in how to document a mystery box on arrival. A plug that died under your heater did what the label said it would.
What This Means When You Order
You should expect a smart plug from a mystery box to be a 10A or 15A unit with a limit printed on the back and a safety mark you should look for, and to use it for lamps, lights, chargers and small appliances rather than anything that heats, pumps or starts under load. Keep it straight in the wall with nothing chained to it, and feel it after the first hour. Ask the seller whether devices in their boxes are powered on before dispatch; Mewoo tests devices before packing and states what its boxes are built around, and any seller should tell you the same.
FAQ
Can I plug a space heater into a smart plug?
Not one from a mystery box. Your typical heater draws 1,500 watts, about 12.5 amps on a 120-volt wall, which sits at or above the continuous rating of most cheap plugs even when the peak figure says 15A; the relay runs hot for hours and the pins are where it fails. Plugs built and listed for heaters exist and say so on the body. If yours does not say so, it stays on lamps.
What does 10A or 15A on the plug mean in watts?
Multiply the figure by your wall voltage. In North America, where the wall is 120 volts, a 10A plug carries roughly 1,200 watts and a 15A plug roughly 1,800; in 230-volt countries the same plugs carry about double. Those are ceilings, not targets: for anything running longer than an hour, keep the load under about 80 per cent, so around 1,000 watts on a 10A plug and 1,400 on a 15A one at 120 volts.
Why can I not plug a power strip into a smart plug?
Because the strip lets you hang more on the plug than its relay can carry without any way for you to see the total. Four small things on a strip can add up to a heater's draw, and the smart plug behind them sees all of it at once. The same goes for extension leads and for chaining one smart plug into another. One device per plug, straight into the wall, keeps the limit visible and the plug cool.
The app says the plug is off but the lamp is still on. What happened?
The relay inside has welded closed, which usually follows a motor's starting surge or a heater's steady heat on your plug, and occasionally happens on a light load when the relay was poor. The plug will never switch off again; unplug it and stop using it. If it welded on a lamp or a fan, that is a genuine fault worth reporting inside the seller's window with a short video of the app and the lamp.
Is a smart plug safe to leave on a lamp all the time?
Yes, if it carries a recognised safety mark on its body and the lamp is an LED or a small bulb; that is the use these plugs are designed for, and a lamp draws a tiny fraction of the rating. Feel the plug after the first hour; it should be no more than slightly warm. Give it a schedule so it is not switching a dozen times a day for no reason.
Can I use it to switch a fridge or a pump on and off?
No. Anything of yours with a compressor or a motor draws several times its running current for a moment as it starts, and that surge is exactly what welds a small relay shut. A fridge also should not be switched by anything that can lose its Wi-Fi. Leave compressors, pumps and air conditioners on their own switches, and use the smart plug for the things it is built for: lights, chargers, fans and small heaters of the mug-warmer kind.
Final Thoughts
A smart plug from a mystery box is a relay with a printed limit, and the limit decides what it can switch: lamps, lights, chargers and fans, with heaters, kettles, motors and power strips kept off it entirely. Read the amps on the back, look for the safety mark, keep long-running loads under 80 per cent, plug it straight into the wall, and feel it after the first hour. Used that way it switches your lights for years.
If you want a tier where smart-home accessories are possible and every device is powered on before dispatch, start with the Triple Reveal Electronics Mystery Box (3 items) or the Party Electronics Mystery Box (6 items). Compare every tier side by side on the electronics mystery box category page.
See whether the smart bulb from a box fits your socket →
