Dear Jim: I know an electric space heater is not as efficient as my central heat pump, but does it ever make sense to use one? If so, which types are the most efficient? – Patrick H.
Dear Patrick: You are correct about their relative cost to use. In my own home, the variable-speed WaterFurnace geothermal heat pump produces more than five dollars worth of heat for each dollar on my electric bill. In contrast, an electric space heater produces just one dollar of heat for each dollar on your bill. This is because the geothermal heat pump efficiently draws most of its heat from deep underground.
Even considering this difference in the operating costs, it can make economic sense to use an electric space heater at times. If using the space heater in one or two rooms allows you to set the heat pump thermostat lower, there can be overall electricity savings. Generally there is no need to keep your entire house toasty warm if only one or two rooms are being used.
Although it is somewhat climate dependent, you can save about three percent for each degree you setback your thermostat for an eight-hour period. The percentage savings is higher in mild climates because the overall heating bills are low. In colder climates, the percentage savings will be lower, but the overall dollar savings are greater for each degree.
All electric space heaters that plug into a 120-volt outlet have a maximum heat output of only about 5,000 Btu/hour; however, the design of the space heat does affect the overall cost of using it. By selecting the proper type of space heater for various situations, it will run for less time to provide the desired heating comfort. If the space heater thermostat switches it off more often or lowers the wattage, less electricity will be used.
You most likely will have several types of space heaters for use in different rooms for different activities. For sleeping, a quiet heater design is best. When just heating one person reading on a sofa, a different design may provide better comfort at a lower operating cost. Before purchasing any, make a list of how you plan to use them and in which rooms.
Convection and radiant are the two basic types of electric space heaters with several subcategories, comfort and safety features in each. Convection heaters use a fan to blow room air over hot coils. The most common and least expensive use ribbon coils (like in a toaster). This type of heater is most effective for heating up the air in an entire room.
For a bedroom, a convection heater with a three-speed fan and a timer is best. Set the fan on high speed shortly before you go to bed to warm the room. When you are ready to go to bed, set the fan to slow speed to minimize the fan noise. Set the timer to shut it off in an hour or however long it typically takes you to fall asleep.
The same general type of heater can be effective for a small room, such as an office or dining room, where the fan sound is not a problem. With the limited maximum heat output from a 120-volt outlet, a space heater may not be effective to heat an entire large living room or one with large inefficient windows, for example.
One with a built-in thermostat is best for small rooms to avoid wasteful overheating. Pay attention to the description. A “programmable” thermostat usually means you can select a temperature setting and it will cycle on and off to maintain it. An “adjustable” thermostat means it can maintain a heat output level, but not a particular desired room temperature.
Radiant space heaters project heat similar to how the sun’s rays can warm you on a cold day. The room air will warm only a small amount, but you will feel toasty warm in front of the radiant heater. I use this type by laptop in my home office. Some use ribbons that get red hot and others use ceramic tubes that glow red.
Radiant heaters are ideal for warming just one person or several close together without having to waste electricity to warm the entire room. Within just one minute, you will feel the heat from a radiant heater and it is totally silent. The far-infrared heat from a radiant heater penetrates room objects and your skin for comfort.
If you plan to use the same heater to warm an entire room or spot heat at different times, select a combination convection/radiant heater. Some ceramic-tube radiant heaters include a low-volume fan and a thermostat to accomplish both tasks. I tall oil-filled design gives off radiant heat in addition to creating natural air convection up over it.
Most space heaters have built-in safety switches to shut off the electricity if they get knocked over. If you are concerned about a young child sticking something in the red hot coils, select a ceramic convection heater. The multiple heating elements never get hot enough to ignite anything.