Convection heaters are electric space heaters that use electric resistance type heat. This simplest method uses electricity to heat small metal ribbons. Then a fan blows air across the ribbons into the room. There are other types such as oil or water filled radiator style electric space heaters.
This type of electric space heaters are often the cheapest to purchase, but have to be balanced against their energy efficiency as they can be the most expensive form of portable electric heaters due to lower energy efficiency.
They also lower the humidity in the room which makes it feel less comfortable and use a fan which increases the wind speed. For comfort, a good humidity level in your home is around 60%. On a dry winter day, convection type heat can lower the humidity level in the home and make you less comfortable as well as increase the static electricity you feel when you reach walk across the carpet and reach for a door knob.
Therefore, you should probably consider other types of electric space heaters for more of a green and energy efficient solution. They can be more dangerous as they do get hot, especially the metal ribbon type. However, they will heat an entire room faster than a similar sized radiant type heater. It will take a little longer to feel that warmth throughout the room as it has to heat the air and objects in the room altogether as opposed to radiant heat which can heat a person or object immediately, but not the air. Hence, the correct choice is dependent upon your application.
Another style of convection heater is the oil or water filled radiator style heater. In general, these are a little slower to heat a room than the electric ribbon type but don’t get as hot and therefore are a safer choice. Unless used for very short periods of time, they are also more energy efficient than the electric ribbon style convection heaters. They also decrease the wind speed you feel with the resistance style heater with a fan blowing across the heating elements.
One hybrid type of radiant and convection heater is the micathermic. These could be a good choice if you want to heat a room or space over a longer period of time and still want the immediate effects of heating and an object or area of the room where people would sit immediately.