Most energy-monitoring smart plugs are rated for 15 amps and 1,800 watts at 120 volts. That sounds like plenty, and for most devices it is. The trouble starts with appliances that run near that limit for hours at a time.
Easy yes: everyday loads
Lamps, TVs, streaming boxes, computers, routers, fans, chargers and most dehumidifiers are comfortably inside a 15A rating. These are also the devices where energy data is most useful, because they’re the ones that quietly stay on.
Space heaters: the big one to avoid
A typical 1,500-watt space heater draws about 12.5 amps at 120 volts, and it can run for hours. The U.S. Consumer Product Safety Commission advises plugging space heaters directly into a wall outlet, never into an extension cord or power strip, to prevent overloading and fire. A plug-in smart plug adds one more connection between the heater and the wall, so the conservative choice is to keep heaters off smart plugs. Check the heater’s manual too. Some plugs are rated lower as well: the Emporia Smart Plug is rated for 10 amps continuous, below what a 1,500-watt heater draws.
Why 15 amps isn’t a free pass
On the multiple-outlet circuits found in most rooms, the National Electrical Code limits any single cord-and-plug appliance that isn’t fastened in place to 80% of the circuit’s rating, which works out to 12 amps on a 15-amp circuit. That’s a good rule of thumb for smart plugs too: keep long-running loads well under the label, and don’t stack a smart plug on a circuit that already feeds a microwave or hair dryer.
Motors and compressors
Read the fine print. Kasa and Tapo list a 1/6 HP motor rating, while Emporia, Eve and THIRDREALITY don’t publish a motor rating on their spec pages. Window air conditioners, freezers and pumps pull a surge when they start, so check the appliance label against the plug’s motor rating before you rely on it.
Quick checklist
Look for a UL or ETL listing, read the plug’s continuous and motor ratings, compare them to the appliance label, and when in doubt, plug the high-draw appliance straight into the wall.
Want to see how a few smart plugs fit with the rest of your setup? Our Whole-Home Energy Calculator adds up what plugs, a thermostat, an energy monitor, an EV charger and a backup battery would mean for your monthly bill.