Space heaters: which type for which room, and the rules that keep them safe

A space heater is for one room, not the house. Every plug-in heater sold in the US tops out at 1,500 watts, because that is what a standard outlet will give it, and 1,500 watts is about 5,100 BTU an hour: a tenth of a small furnace. So every heater on this site makes the same amount of heat. What you are choosing is how that heat is delivered, how quiet the delivery is, how well the thermostat holds a temperature, and how the thing behaves when it falls over or gets covered.

Four designs cover the market. Ceramic fan heaters, the Lasko 754201 and the Dreo Atom One, push hot air at you within a minute and are the loudest of the group; they are the heater for a desk or a chair, not a bed. A vortex heater like the Vornado VH10 is a ceramic heater with a fan built to stir the whole room, so the far corner warms too instead of the six feet in front of the grille. An oil-filled radiator, the De'Longhi TRD40615T here, has no fan at all: it takes twenty minutes to feel like anything, then holds a room in silence. Oscillating towers like the Lasko 5586 sweep a sofa. Propane heaters are a separate category with their own rules further down.

Match the design to the room. Bedroom: the oil-filled radiator, because it is silent and has nothing that glows; the Dreo is the alternative if you want a thermostat you can set in degrees and can live with its button beeps. Office or desk: the small Lasko, which is the cheapest heater here and loud enough that you will not forget it is on. Living room: the Vornado for even heat, or the Lasko tower if you want a remote and oscillation. Nursery or a room with a toddler: the oil-filled radiator again, for the same reasons, kept behind furniture. Bathroom: none of these; a bathroom heater needs a shock-protection plug and a rating for wet rooms, which none of the heaters on this page carry.

The fire-safety bodies publish the same five rules every winter, and the home-fire data behind them does not change: space heaters cause fewer than half of home heating fires and the large majority of the deaths. One, three feet of clear space in every direction, which rules out the spot beside the bed and the corner by the curtains. Two, straight into the wall outlet. Never a power strip, never an extension cord, never the same outlet as anything else. Three, on the floor, on a hard, level surface; the tip-over switch only works if the heater can tip, and a heater wedged on a rug or a nightstand can fall without triggering it. Four, off when you leave the room and off when you sleep. Five, nothing on top of it, ever, including the glove you are drying.

Rule four is the one people break, so break it carefully. If a heater runs while you sleep, make it the oil-filled radiator: no fan to fail, no element glowing at a thousand degrees, a sealed body, and a thermostat that cycles instead of running flat out. Its fins get hot enough to hurt a hand, so it still gets the three feet. Set the thermostat low and set the timer to shut it down an hour before you wake; the room holds the heat. A heated mattress pad or an electric blanket draws about a tenth of the power and warms the only thing that matters, which is the bed; it is the better bedroom answer for most people.

The circuit is the part nobody thinks about. A 1,500-watt heater draws 12.5 amps, and a bedroom circuit is usually rated for 15. That is the whole circuit: add a hair dryer, a second heater or a microwave on the same run of outlets and the breaker trips, and if it does not trip you have a problem worth an electrician. Feel the plug after an hour. Warm is normal; hot means a worn outlet, and the fix is a new outlet, not a different heater. The extension-cord rule exists because a cord sized for a lamp, carrying 12 amps for eight hours, heats like an element.

Set a temperature, not a power level. Running on high with no thermostat does not warm the room faster once it is at temperature; it just keeps buying heat the room then loses. The Dreo and the Lasko tower give you degrees; the Vornado, the De'Longhi and the small Lasko give you a dial with no numbers, which the owners of all three complain about. Find the mark once and put a pencil tick on it. On running cost: a heater on high uses one and a half kilowatt-hours every hour, and your bill shows what your utility charges for one. A heater that runs all winter to make up for a cold house is a sign the house, not the room, needs the fix: a draft under the door, a register closed in the basement, or a duct that needs balancing.

Propane heaters are not room heaters. The Mr. Heater Portable Buddy and the Big Buddy are for the garage, the ice shanty, the deer blind and the night the power goes out. Both have an oxygen sensor that cuts the gas when the air gets thin and a tip-over shut-off, and both burn clean enough to be rated for indoor use in most states; Massachusetts bans unvented propane heaters indoors outright. Indoor use still means a window cracked, a carbon monoxide alarm in the same room, nobody asleep, and the 1-pound cylinders only. The 20-pound tank and hose kit are for the shanty and the open garage; fire code keeps bulk cylinders out of living spaces. The Buddy's pilot stops holding once dust reaches the sensor, so blow it out with canned air before the season. Above about 7,000 feet the oxygen sensor shuts either heater off and keeps doing it.

The Portable Buddy covers a one-car garage or a shanty on a 1-pound cylinder for three hours on high. The Big Buddy doubles the output for a two-car garage and takes two cylinders; note that the maker dropped the built-in fan from current production without changing the price, so older reviews describe a feature the heater on the shelf no longer has. Neither is for a bedroom, a tent you are sleeping in, or a car.

Skip the heaters sold on output claims above 1,500 watts; a plug-in heater cannot make more. Skip the wooden infrared cabinets sold as furnace replacements for the same reason. Skip anything without a tip-over switch and an overheat cut-off, which excludes most of the no-name imports. Buy one heater for the room that needs it, keep it three feet from everything, and put the rest of the money into the draft strip for the door.