Are Large Heaters More Powerful Than Small Ones?

Nope! It may seem counterintuitive, but large heaters don’t necessarily heat any better than small ones.

Whatever their physical size, most space heaters in the US and Canada deliver about the same amount of heat. Space heaters top out at 1,500 watts, which is the highest safe operating load for a 15-amp household circuit. And aside from some low-power personal heaters here and there, most space heaters you’ll find on the market are 1,500-watt heaters.

What’s more, electric space heaters are all pretty much 100 percent efficient in converting that electricity to heat. Whether directly or indirectly, nearly all of that energy will eventually become heat.

So if space heaters are the same power and the same efficiency, why are some 1,500-watt heaters advertised for small rooms and some for large rooms? This likely has as much to do with marketing as science. Pretty much every ceramic, electric-coil, or PTC heater has about the same amount of juice and thus the same ability to heat a room … at least eventually.

What differs among heaters is how and where the heat gets distributed and how fast. All other things being equal, the efficacy of a heater is mostly about whether it puts the heat where you want it to go.

What Are the Different Types of Space Heaters?

Basically all electric space heaters do the same thing: They take electricity off the grid, usually 1,500 watts of it if you’re in the United States, and turn that power into heat.

The vast majority of space heaters, including ceramic heaters and PTC heaters, are electric resistance heaters. This means they run an electrical current through something that creates resistance: maybe an electric coil or maybe a specially designed ceramic. This quickly turns electricity into heat.

Most space heaters use a fan to disperse this heat out into the world, where we all live. These forced-air convection heaters tend to be the fastest at quickly raising the temperature of the surrounding air. The air then heats you. And so while this variety heats quickly, it can take quite a bit of electricity to heat up a whole room.

Oil-filled radiators, in contrast, heat up oil that circulates inside the device, which then emits heat to the surrounding room. These tend to heat up slower but offer even and lasting heat and are very quiet. These radiators operate on the same principle as steam radiators in buildings with a boiler room. And just like steam radiators, they can get really, really hot to the touch.

Radiant heaters, such as infrared heaters, operate much like the sun or a campfire: Rather than heat the air, they heat objects or people directly by radiating energy toward them. Infrared devices heat the air only indirectly, via the objects it heats— much the same way the sun’s heat radiates off baking city streets. The glow is immediately palpable as warmth, but you’ll need to be in the path of the radiation to feel it, and the thermometer might not immediately register the warmth you perceive. Infrared heaters tend to be best at making an individual in front of the heater feel a little warmer without using a lot of energy, making them a more common decision in large and lofty spaces or outside on a patio.

Though they deliver heat differently, both infrared and oil-filled heaters are subject to the same wattage limitations, and have about the same efficiency, as electrical resistance heaters.

The same cannot be said for heat pumps, a newer technology that’s expected to provide the next generation of household heat. Heat pumps don’t use energy to create heat. Instead, they move heat energy from one place to another. Accordingly, they require far less energy than other forms of heater. But household systems cost thousands to install. And while more affordable window and portable heat pumps are ramping up, they’re not yet broadly available.

How We Tested and What We Tested

When it comes to testing space heaters, there are a few main questions: How safe is it? How loud is it? How quickly and evenly can it heat a room?

During intensive testing of dozens of space heaters, I lived for weeks in a home with the thermostat set to a chilly 65 degrees Fahrenheit.

I tested how well and quickly each device heated a medium-size room (14 by 14 feet), and also how well it heated a small seating area in a larger, open-format space. To test each heater’s thermostat and also measure the evenness of heating, I placed thermometers at three or more locations in each room, including behind the heater.

I tested the loudness of each device with a decibel meter at 3 feet away and verified power usage with a wattmeter. To see whether the heater’s exhaust put out painful levels of heat, I used an infrared thermometer to gauge precise surface temperatures. When in doubt, I put my own fingers on the line.

Finally, I tested safety features and basic durability. I looked at independent safety certifications, of course. But I also rudely knocked over each device to verify how the device’s tip-over protections functioned, if at all, and verified that the device started working again when set back on its feet.

To test overheat protection, I smothered each device with an old sheet to see whether the device shut itself off or whether it adjusted its power output to keep internal temperature low. After the device shut itseld off, I then checked how soon it could turn back on, if it ever did. (Some heaters gave up, in permanent complaint!)

If any device fails the tip-over or overheat tests, we don’t recommend it. If it’s significantly louder than 50 decibels at 3 feet, we don’t recommend it. If the heater breaks during routine operation, we don’t recommend it. Maddening rattles and squeaks are also disqualifying.

We keep on testing our favorites through the cold season and beyond, to see how they hold up over time. And, of course, we continually subject more heaters to our testing regimen to see if other devices can oust our current faves.