The number on the label decides everything: most smart plugs document 15A/1800W maximum resistive load — the ceiling of a standard US outlet circuit. Under it: lamps, fans, chargers, TVs, humidifiers, Christmas lights. Over or wrong-type: space heaters (a documented fire pattern when plugged through anything), hair dryers, and — different problem — refrigerators and air conditioners, whose compressors demand relay ratings most plugs don't document. The catch: exceeding the rating doesn't trip an alarm; it heats the relay silently, the documented failure mode behind smart-plug melt photos.
Blog Daily publishes information, not electrical advice — ratings below come from manufacturer documentation and UL listing requirements; anything beyond a lamp-class device on a smart plug deserves an electrician's opinion.
The documented categories
| Appliance | Typical draw | Smart plug verdict |
|---|---|---|
| Lamps, fans, chargers | <150W | Perfect — the designed use |
| TV, router, humidifier | 30–300W | Fine; consider energy-monitoring plugs |
| Coffee maker (resistive) | 600–1200W | Usually within rating; check the plate |
| Space heater | 1500W+ | Never — continuous max load through a relay; documented fire pattern |
| Hair dryer / kettle | 1200–1875W | No — brief but at/over the ceiling |
| Refrigerator / AC compressor | Surge 3–10x running amps | Only heavy-duty plugs documenting motor/inductive ratings (20A class, e.g. purpose-built heavy-duty models) |
| Washer / EV charger | Circuit-dependent | No — dedicated circuits, not smart plugs |
What does "inductive load" mean here?
Resistive loads (heating elements, lights) draw steady current. Motors and compressors draw a documented startup surge several times their running draw, and their coils produce kickback when switching off — both stress the plug's relay beyond its resistive rating. Plugs that document "motor load" or "TUV/UL rated for HP" listings exist specifically for this; a generic 15A plug on a garage-door opener or fridge is a documented gamble even when the running watts seem to fit.
What are the safer alternatives for heavy appliances?
- Heavy-duty smart plugs (documented 20A / 240V / motor ratings) for specific qualified loads.
- Smart relays wired by an electrician — the Shelly/Matter relay class documents direct-wire control for water heaters and AC, installed inside the appliance's circuit.
- Energy-monitoring plugs for insight instead of control: measuring a fridge's draw documents whether it's the lamp or a dying compressor — useful even when you don't switch it.
What else belongs in the safe-use list?
- Indoor plugs stay indoors — outdoor smart plugs document weather-resistant enclosures; indoor units corrode and short.
- One plug, one appliance — power strips through smart plugs multiply loads and violate the documented single-device intent.
- UL/ETL listing check — unlisted plugs document nothing; the certification mark is the floor.
The verdict
Lamp-class loads: any reputable smart plug. Heating and motors: check the plate, then the plug's documented ratings, and when the numbers are close — don't. What the sources did not establish: any safe way to run a space heater through a relay; that category documents its own answer.
FAQ
For more context, read How to Fix a Smart Home Device That Keeps Going Offline.
For more context, read What Matter Actually Does for Your Smart Home, Explained.
For more context, read How to Set Up Matter and Thread in Your Home, Step by Step.