Convection heaters and radiant heaters are both very popular options for spot-heaters. These small, portable heaters are used to add heat to a cool space in a room or office where the heating system is not providing enough heat. Oil-based versions use a combination of electricity and burning oil to create heat, while electric versions use a ceramic element, but the real difference is between convection and radiant versions.
Convection heaters use the air to move heat throughout a room. This is why many convection heaters have fans: they take in air, circulate it around the inside of the heater and allow it to absorb the heat that the heating element is producing. The air then passes out into the room and raises the air temperature. The air can pass into other rooms and heat a large area, but this will also dissipate its effects.
Oil-based Radiant Heaters
Radiant heaters heat with infrared light produced by combustion and other processes. Oil versions use electricity to heat the oil until it burns, and the heat is channelled into panels or tubes that radiate it outward. This system tends to only heat the areas that are exposed to the radiating heatwaves, allowing the heater to be more focused on a single room or space. The temperature of the air does not effect the operation of a radiant heater.
Convection heaters can do a very good job of heating an entire room, but only if the heated air stays within that room. If the air escapes outdoors, then the heater's efficiency becomes quickly impaired. If the room is badly insulated or has pathways where air can easily escape, then oil radiant heaters are the best method of heating the room.
In terms of speed, electric convection heaters tend to be much faster. Their elements heat up quickly and produce heat only a short time after being turned on. Oil-filled radiators take longer, because the oil must be heated up before it can be used. If immediate heat is a necessity, then convection heaters may be a better option.
Because oil-filled radiator heaters also require electricity to heat and combust the oil, they end up using about the same amount of electricity for the heating process as the convection versions. However, because convection heaters also use fans to circulate air, they tend to take more electricity to operate overall.
Both oil and electrical element heaters can be either convection heaters or radiant heaters. Oil heaters do not have to be radiant, and there are many convection versions available. Likewise, element heaters are often used in radiant systems.