Electric baseboard units have heating elements enclosed in a slotted metal housing. When the thermostat calls for heat, a circuit closes, energizing the heating elements. Air surrounding the elements is heated and begins to rise by convection, drawing in cooler air from beneath the elements. This movement of air continues to heat the room air until the thermostat is satisfied.
The baseboard unit also generates some radiant heat. The hot heating element and metal housing radiate heat directly from the unit to objects in the room.
The heating element resembles a rod hanging on hinges. Aluminum fins along the length of the element speed the transfer of heat to the air by increasing the surface area of the heating elements and thereby increasing the convection flow.
Baseboard heaters are commonly installed along the bottom of outside walls, often under windows (where heat loss is greatest). These units are surface-mounted and can be installed after walls are finished. In bathrooms and kitchens they can be installed as kick-space heaters set into the spaces beneath cabinets.
They are the least expensive heating system to install and they tend to be popular in very well-insulated homes, because they can be sized to match the load very easily. Since no flues or chimneys are required, you will not have to put holes in walls or roofs.
There are disadvantages to baseboard heat. They satisfy thermostat calls rather slowly, they are easily blocked by furniture, and it is hard to control air circulation.