Portable Electric Heaters
Helping Customers Understand Portable Electric Heaters
(Separating Advertising Claims from Fact)
By Richard Hiatt, NFEC/RERC
If one of your customers asked you which of the three electric heaters below delivers more heat, do you know the answer? We'll tell you later in this article, but nearly everyone is surprised. With the vast number of electric heater styles, shapes and sizes on the market, it's no wonder that consumers are confused when shopping for the right one to fit their needs. Adding to the confusion are the exaggerated claims by a few advertisers, who boast their product has an "exclusive design" that will "save you big bucks on your heating bill". A least one manufacturer claims it can cut heating costs up to 50% with its "space-age technology".
Which portable electric heater delivers more heat? The answer is at the end of this article, but this is a common customer question.
With all the choices, it's logical that customers would turn to their electricity supplier as the expert in selecting the best type of heater. As energy professionals, power suppliers should be able to explain the key factors to consider, and help consumers see through the marketing hype.
Describing Three Main Heater Designs
The first step is to understand the three main heater categories, listed below. Starting with the "High-Temperature Radiant" style. They are characterized by the glowing red heating elements, and shiny mirrored reflector behind the coils. Radiant heaters don't attempt to heat the air, but rely on "beaming" their warmth directly to people or objects in the room. Just like the sun's warmth, it can be a very pleasing form of heat.
The second category, after the radiant group, is the "Natural Convection" style, which transfers heat differently. Instead of using red-hot coils, they distribute the same amount of heat over a wider surface of the heater. This allows the flow of air over their surface (natural convection) to transfer heat to the air. Often seen in a long slender baseboard design, these heaters are warm to the touch but not hot enough to burn you. One example of a natural convection heater is shown in the adjacent photo. Other convective heaters are shaped like old-fashioned cast iron radiators, as found in historic buildings. An oil-like fluid inside spreads the heat around the full surface of these portable heaters. On a watt-far-watt equivalent, natural convection heaters put out just as much warmth, but you don't feel the intense heat as from a radiant design.
The third category, "Fan-Forced Heaters" relies on a blower to push air over the heating coils. Designed like a "mini furnace", these heaters must warm the air in the room to increase comfort. Unlike the natural convection style, they don't rely on a large surface area to transfer their heat to the air. That is why fan-forced heaters are often smaller in size than the other designs.
A quick clarification - small fans are sometimes used in radiant heaters too, as a way to circulate the air. Don't let the presence of this small fan fool you; if most of the heat radiates out from visible glowing coils, it's a radiant heater.
A Watt Is a Watt, No Matter How It is Delivered
Each of the three designs described above uses a process called "electric resistance heating". This simply means that electricity is sent through a material that is "resistant" to the flow of electric current. These materials glow red as they convert electricity into heat (visualize the elements on a stove). Because all electric heaters use this same process, they all have the same efficiency -100%.
There are no losses. Whatever the heater's shape, size, or marketing claims, the amount of heat coming out is the same as the amount of electricity going in. Therefore, any two heaters with a rating of 1,500 watts on the nameplate will deliver the same amount of heat, no matter what they look like.
What is different is the method used to transfer the warmth from the heating elements to the person or objects that need it. One of the three methods explained above will always be employed, so this helps you answer the customers question. The method of heat transfer will determine If it's a good fit for the customer's needs.
For example, the radiant style heater can be a good choice, but only If you understand its strong points and limitations. Radiant heaters "shine" their heat energy in a very defined area. Therefore, if the air temperature in a room is cold, only the objects in the path of these radiant waves of energy will feel warm. Much like a fan won't keep you cool unless you stand in its airflow path, a radiant heater won't do you much good if you're not within reach of its warming rays.
Radiant heaters can be a good choice for farm shops, garages, machinery sheds, and in the form of heat lamps. Their instant heat is particularly handy because a central furnace is not needed (nor economical) in large buildings that are seldom occupied.
Zonal Heating To Save Energy
Any of the three portable electric heater types can allow room-by-room variation in temperature. This "zonal heating method" can save energy, but only by lowering the setting on the home's central heating thermostat. Then in the occupied room(s), a space heater is used to boost the temperature to a comfortable level.
The success of this strategy is somewhat dependant on the home's floor plan. For a home having a very open floor plan (few dividing walls), it's difficult to close-off unoccupied rooms. The key to this zonal heating method is to be able to lower the temperature in a large percentage of the house, for most of the day.
To help NFEC members separate the facts from advertising claims, we are developing a simple brochure that can be used as a customer handout. Unlike other guides on electric heaters that focus only on safety, this one will be a straightforward guide to describe the three main categories of electric heaters. It will help consumers compare the heating ability of each by wattage output and other important features.
Final note: The answer to our original question about the heaters listed at the beginning of the article is this. All three heaters are rated at 1,500 watts, so they all deliver exactly the same amount of heat energy. They also have exactly the same efficiency -1 00%. The only difference is how the heat is conveyed to the user, either by a focused radiant heat, or by warming the air that travels across the heating surface.