A heater can use radiation, convection, or both, depending on the type. Radiant heaters emit infrared radiation that warms people and objects directly, while convection heaters warm the air in a room and let it circulate. Most household heaters lean primarily on one method, though nearly all involve some degree of both.
How Radiant Heaters Work
Radiant heaters produce infrared radiation, the same type of energy you feel standing near a hot stovetop from across the room. This radiation travels in straight lines and heats whatever it lands on: your skin, clothing, furniture, floors. The air between you and the heater stays mostly unheated. It’s the same principle as feeling the sun’s warmth on a cold day. The moment you step into shade, the warmth disappears.
Because radiant heaters work on a line-of-sight basis, you’ll feel the most warmth when you’re close to the panel and directly facing it. This makes them excellent for spot heating, like warming yourself at a desk or on a patio. They deliver warmth almost instantly since they don’t need to raise the temperature of an entire room’s air first. The tradeoff is that they won’t evenly heat a large enclosed space the way a convection heater can.
Common radiant heaters include quartz heaters, infrared panel heaters, and the glowing bar-style heaters you’ve probably seen mounted on restaurant patios. The infrared wavelengths they emit range from near-infrared (shorter wavelengths, higher intensity) to far-infrared (longer wavelengths, gentler warmth). Far-infrared models typically raise skin temperature to a comfortable 32 to 35°C, which feels pleasant without being intense.
How Convection Heaters Work
Convection heaters warm the air itself. A heating element (ceramic, metal coil, or oil-filled fins) heats air in contact with it. That warm air rises because it’s less dense, cooler air flows in to replace it, and a natural circulation loop forms throughout the room. Some convection heaters add a fan to speed this process up, which is called forced convection.
The result is a gradual, even rise in room temperature. Unlike a radiant heater that warms only what’s in front of it, a convection heater raises the ambient air temperature everywhere in an enclosed space. The downside: it takes longer. You might wait several minutes before a convection heater makes a noticeable difference, especially in a larger room. Oil-filled radiators, ceramic fan heaters, and baseboard heaters all fall into this category.
Some Heaters Use Both
The line between radiant and convection isn’t always clean. A traditional hot water radiator, despite its name, actually delivers a mix of both: it radiates heat from its hot surface and warms the air around it, creating convection currents. Radiant floor heating systems are another good example. According to the U.S. Department of Energy, radiant floor heating depends heavily on convection, because the warm air generated at floor level naturally rises and circulates through the room.
Even a purely radiant heater will warm the air to some extent, since the objects it heats eventually release that warmth into surrounding air. And convection heaters radiate a small amount of heat from their hot surfaces. The question is always which mechanism dominates.
Choosing the Right Type for Your Space
Your best choice depends on what you’re trying to heat and how quickly you need it.
- Small or open spaces: Radiant heaters shine in garages, patios, workshops, or rooms with high ceilings where warm air would just rise and escape. They’re also ideal when you only need to warm one or two people rather than an entire room.
- Enclosed rooms: Convection heaters work better for bedrooms, living rooms, and offices where you want consistent temperature throughout. They keep the air stable once they’ve had time to warm it up.
- Quick warmth: If you want to feel heat the moment you turn the heater on, radiant is the clear winner. Convection heaters need time to build up room temperature.
- Air quality: Radiant heaters don’t circulate air, which means they don’t stir up dust. If you’re sensitive to airborne particles, this can matter.
Energy Use and Efficiency
Most portable electric heaters, whether radiant or convective, draw about 1,500 watts at full power. At the average U.S. electricity rate of 16 cents per kilowatt-hour, that works out to roughly 24 cents per hour. Running one for five hours a day costs about $36 per month.
The efficiency differences between radiant and convective systems are more about how they deliver heat than how much electricity they consume. Radiant heaters waste less energy in short-use situations because they warm you directly without needing to heat an entire air volume first. Convection heaters can use more energy in drafty or poorly insulated spaces because warm air escapes easily. In a well-insulated room where you want all-day warmth, convection performs well because the heated air stays put. Research from the European HVAC engineering body REHVA found that convection-dominant emitters in buildings required several percentage points more energy than radiator-style emitters, with the gap being larger in older, less insulated buildings.
Safety and Placement
Radiant heaters get hot on their front-facing surfaces, which means placement matters more. Keep at least 3 feet of clearance in front of any heater and 6 inches of clearance on each side and above it. This applies to both types, but it’s especially important with radiant models since they concentrate intense heat in one direction. Keep them away from curtains, furniture, and anything flammable.
Convection heaters, particularly oil-filled models, tend to have lower surface temperatures spread over a larger area. They’re generally considered safer around children and pets for this reason, though they still need adequate clearance from combustible materials. Regardless of type, look for models with tip-over shutoff and overheat protection.