In terms of energy efficiency, space heaters are great for adding supplemental heat when the main heating source is inadequate or when central heating may be too costly to install or to operate. In fact, the use of a space heater may even be less expensive to operate if it's only used to heat a small room or area, or to boost the temperature of rooms used by individuals sensitive to cold. Space heaters do not lose any energy through ducts or combustion, so they're considered to be almost 100% efficient. Almost all of the warmth generated by a space heater will radiate into a room.

For industrial areas such as warehouses and workspaces, fueled heaters such as kerosene and propane heaters are great because they use little to no electricity. However, these cannot be used in areas without adequate ventilation, and they can carry some safety risks.

For home use, electric space heaters are more suitable. Most electric space heaters use convection to heat a room.  When used as a supplemental heat source in combination with an existing central heating system, portable electric space heaters can be very affordable.  As well, some electric heaters also rely on radiant heating, meaning they emit infrared heat in the same way the sun warms the earth. Only the objects around the heater are warmed, and for this reason, the use of these heaters can be very energy efficient, as an infrared heater immediately transfers heat to occupants and not the entire room or area. These heaters can also heat up a room or area much faster, as heat is easily directed to the space being heated in a precise beam. 

Lastly, consider the use of an oil-filled radiator heater.  Like electric space heaters, oil-filled heaters are ideal when your central heating system is not sufficient.  These are safe, silent, and energy efficient because they automatically maintain optimal room temperature. 

Therefore, with all of the above heating choices available, you can still save money on your energy bill and keep your home or living space comfortable.  For additional money savings, follow these tips as well:

1. Choose a heater with a timer or that is thermostatically controlled, such as the Newair AH-510E. These heaters can avoid the energy waste of overheating a room.

2. Purchase a heater of the proper size for the room or area you wish to heat. Do not choose an oversized heater, and pay attention to watts. With a 10/1 ratio of watts to square feet heated, a 1500 watt space heater (120 volts) will heat an insulated area of 150 square feet, and a garage heater rated at 5,000 watts should heat an area over 400 square feet.

3. Try not to leave your space heater on the high setting, and turn the heater off when you are away.  Space heaters can consume large amounts of energy if left on continuously.

4. Keep your doors and windows closed in order to minimize heat loss and for optimal heating effectiveness.  Frequent switching a heater on and off and adjusting the thermostat will also increase energy usage.