Smart plugs are probably the best smart home upgrade of them all, turning dumb old devices like lamps and fans into modern connected ones that you can automate. But they also have one dangerous limitation, which is why some devices should never be used with them.
Most smart plugs are rated for 10A loads
The vast majority of smart plugs top out at a 10 Amp load. Amps are a measure of current, while Voltage (V) refers to electrical “pressure.” By multiplying Volts by Amps, you’ll get the total power draw of a device in Watts (W).
So on the standard North American power grid, a smart plug that can handle 10A of current on a 120V supply can safely handle a power draw of 1200W at any given moment. In other regions, where the power supply can be as much as 240V, this can double to 2400W.
These limits will be printed on a smart plug. Some plugs may handle loads of up to 15A, but you should always check the plug to be sure. I have a home full of IKEA’s Zigbee smart plugs, and they’re designed for relatively low-power devices, which cap out at 10A.
Exceeding this power rating can be dangerous. Since the plugs are only designed to handle so much power, exceeding these limits can cause them to overheat and potentially catch fire over prolonged periods of use. They can melt and become stuck to the wall socket, or even cause damage to whatever appliance they are connected to.
For most devices, this isn’t a problem. Lamps, fans, power tool batteries, network equipment, and even appliances like dishwashers and washing machines all typically remain within the safe operating range of this 10A limit. But some pose a real risk.
How to figure out which devices are safe
Generally speaking, appliances that heat, cool, and are associated with large power spikes should not be connected to a regular smart plug. This typically includes clothes dryers, air conditioning units (including many portable ones), electric vehicle chargers, cooktops, ovens, water heaters, radiators, and pumps.
Though some of these devices may remain within safe limits under normal operation, some are associated with surges in power on startup, which could still be dangerous.
To find out what sort of power usage is associated with a device, consult any documents you got with the device, the box, or the manufacturer’s website. Many devices will also have their power requirements written on them, so check around the back of the machine.
If in doubt, avoid using a standard household smart plug with these devices. At the same time, be mindful of the combined load for any extension cord or power strips you have connected to a smart plug. A few lamps connected to a bank isn’t a concern, but a whole entertainment unit’s worth of devices that are used simultaneously could push you over the safe operating limit.
This advice applies to extension cords and power banks, which often double as surge protectors.
What to use instead of a standard smart plug
Thankfully, there are solutions for the automation of high-power devices. You can go two routes: use a heavy-duty plug or switch that is designed to handle increased loads, or use a hard-wired relay. Neither route is particularly expensive, though you should be mindful of the legal requirements for electrical work where you live before you start pulling wires out of the wall and installing relays.
Companies like Shelly offer a standard smart plug that can handle 15A or 1800W for $20 and communicates over Zigbee, Wi-Fi, and Bluetooth with support for Matter, HomeKit, and Home Assistant. Zooz offers an alternative in the form of a heavy-duty energy monitoring smart switch ($49) that uses Z-Wave to communicate with Home Assistant and other smart home servers.
Relays do away with plugs completely and do their job while being completely hidden from view, though you can use them in conjunction with standard switches to maintain standard local control. A relay like the Shelly 1 Gen4 can handle power loads of 240V at 16A for $22.
If you need something seriously heavy-duty and weather-proof, give the Aeotec Heavy Duty Switch ($106) a look. Capable of handling currents of up to 40A, this is perfect for charging an electric vehicle on your terms (like when the sun is shining and your solar panels are powering your home).
There are many more smart plugs, relays, and switches on the market that can be used with your smart home system of choice to intelligently control high-power-draw devices.
If you think you’ve had a device connected to a regular smart plug for a while with no ill effects, now is the time to rectify the problem.
Stephan is the sports journalist for the Maple Grove Report.
