Energy-Efficient Space Heaters

by Nick Gromicko, CMI®
Why use space heaters?
Small, portable space heaters are often used when the main heating system is inadequate, or when it would be too costly to operate or install central heating.  They can also be useful to supplement adequate central heating in certain instances, such as heating one room that will be primarily occupied while lowering the thermostat on the central system so that heat is not wasted in unoccupied rooms.  In some cases, it is possible to lower total heating costs by up to 10%, as well as reduce COemissions by up to 800 pounds, by using space heaters in this manner.

Different Types of Space Heaters

Understanding some of the differences between the types of space heaters and how they work can be helpful when deciding what the most efficient and effective options are for a given situation.  
Here are some of the main types of heaters available: 
  • coil-based convection heaters: This type of heater uses a fan to push air into a room that has been heated internally by passing through hot metal coils. These heaters utilize a safety mesh in order to ensure that nothing in the room will come into contact with the internal heating elements.

  • ceramic-element heaters: This type is generally considered safer to operate than a coil-based unit. Since the ceramic core is larger than heating coils, these units can operate at a lower temperature while providing an equivalent amount of heat that spreads over a farther area. This type of heater is also able to maintain a higher temperature for a longer period of time compared to a coil-based unit, which makes it more efficient.

  • oil-filled radiators: These heaters are highly efficient and operate silently because they do not use a fan. Instead, they use fluid contained in a permanently sealed radiator apparatus, which does not ever need to be refilled. The oil is heated within the unit, and the heat from the oil then radiates into the room. Once heated, the oil will continue to gradually release warmth into the room even when the internal heating element is turned off.

  • halogen lamp heaters:  Energy-efficient halogen bulbs are used in these types of space heaters to provide instant warmth at the touch of a button.  They are made safe by employing safety grilles and cool cabinets, and can be especially appropriate in areas where small children or pets are of concern.

Estimating the Cost of Operation

The operational costs of space heaters depend on the type of heater in use, as well as the room it is being used to heat.  "Kilowatts x Rate x Time = Cost" is a useful formula, in general, to determine how much a heater will cost to run.  Here is how the formual breaks down:

  • kilowatts: the setting of the heater. Divide watts by 1,000 to get kilowatts per hour;
  • rate: the cost of electricity per kilowatt-hour, which can be determined for an area by contacting the local utility company; and
  • time:  the amount of time the heater is in use.
For example, a 1,500-watt space heater running for 10 hours at a rate of $0.10 per kilowatt-hour will cost $1.50.  Using the formula:
Kilowatts x  Rate x Time = Cost,
the usage can be figured as:

(1,500w ÷ 1,000) x $0.10 kWh x 10 hours = $1.50.

Space Heater Safety

Since space heaters can generate extreme temperatures at the surface, they have the potential to be dangerous and even cause injury.  Although they are safe when operated correctly, it is estimated that 25,000 residential fires and 300 deaths are associated with the use of space heaters every year.  When using a portable space heater, following these safety precautions, as well as any guidelines recommended by the manufacturer of the unit, can lessen the risk of accident or injury.

  • Use only the type of fuel or energy intended for use with the specific device.  The use of gasoline in a kerosene heater, for example, would be very dangerous.
  • Never attempt to repair or replace parts in a heater yourself.  This should always be handled by a qualified service center, since the results of repairing a malfunctioning unit could be dangerous.
  • Use of extension cords for the power supply should be avoided.  A cord marked 14 or 12 AWG can be used if absolutely necessary.
  • Do not use space heaters in wet or moist areas, such as in a bathroom.
  • Always keep heaters level and on the floor.  If a heater has been placed on furniture and it falls off, or if a table it has been placed on collapses, the damage to the unit could result in a fire or shock hazard.  Some units contain a tip-over switch which automatically shuts the power off if the unit is knocked over, but even these should be situated in such a way that they will not be at risk of falling over.
  • If the surface of the unit has a high operating temperature, there should be a guard around the heating element to keep people, pets and combustibles a safe distance away from it.
  • The unit should have an indicator light to signal when it is plugged in or turned on.
  • Be sure to install the correct size unit for the space to be heated.  Too large or small of a unit may actually decrease energy efficiency, or could cause pollutants.

Other Factors to Consider

When considering the use of a space heater, especially for the purpose of improved energy efficiency, there are several final factors to consider.  Space heaters will only impact energy efficiency in a positive way if they allow for the home's main thermostats to be turned down.  If a space heater is used simply in addition to central heat without lowering the central thermostat, it will only add to energy bills.  
Here are some other things to take into consideration when deciding whether a space heater will be right for a given situation, and which type of space heater will work best.
  • What area of the building will the heater be used in?  Be sure to select an appropriate unit for the area, and carefully consider whether this area will really benefit from use of a portable heater to begin with.  For example, heating a room that is generally too cold but not often used anyway would simply suck energy without much return on savings. 
  • Space heaters that include a thermostat are more efficient than models that do not.
  • If the unit doesn't have a thermostat, utilize the different settings on it for maximum efficiency.  Once a heater has adequately heated a room at full power, turn the setting lower to maintain current levels, rather than adding more heat to an already warmed room.
  • Select a heater with appropriate safety features for the application.  For example, a heater that achieves extremely hot surface temperatures may not be a good choice in an area where small children are present.
  • The surface temperature of the heater can also be an issue in areas where combustibles might be found in close proximity to the unit.
  • Some units that use a fan can be noisy, which may be an issue in certain circumstances, and should be taken into account during the selection process.
Space heaters can be effective energy-savers under the right circumstances, and different types of units will perform better in different situations.  Knowing a bit about acceptable applications, as well as the properties of different designs, can be helpful in deciding if the use of a space heater will be a good choice for a home.