clock menu more-arrow no yes mobile
Portable space heater at home iStock

A few years ago, we began to notice two closely related trends. First, each season's heating bill was significantly higher than the previous season's. Second, huge pyramid displays of portable space heaters began to appear in home centers, discount stores, appliance stores, and even chain drug stores. Most of us know how good heat from one of these small appliances feels when it's sitting a few feet away.

But portable heaters raise a number of questions as well. Among them: Do portable space heaters actually reduce overall energy bills? And, given how hot they get, are they truly safe? We decided to investigate.

Cost of Portable Space Heaters

We wish we could tell you unequivocally that turning down your furnace and using a portable heater will save you money, but the reality is more complicated. Some folks will save money, others won't, depending on the price of fuel in their area, the climate they live in, the size of their home, its insulation levels, and the age and efficiency of their furnace.

Some manufacturers claim that their heaters can slash heating bills by 20 percent. Nelson Stevens, an energy-management specialist at Lincoln Electrical Systems in Lincoln, Nebraska, says that's entirely possible in his area. According to Stevens, "turning down the thermostat 10°F and using a space heater for six hours a day can cut heating costs by 19 percent." However, the cost of electricity in Lincoln is about 5 cents per kilowatt-hour (kWh). "In areas like Chicago or Boston, where it's 8 to 10 cents per kilowatt-hour, the savings would be a lot less," he says.

Michael Lamb, a certified energy manager at the Energy Efficiency and Renewable Energy Clearinghouse in Merrifield, Virginia, agrees that it's nearly impossible to provide an average savings figure. But he points out that there are times when space heaters don't make sense. "If you have a small, tight house, an efficient gas furnace is cheaper to run than a pair of space heaters," he says.

Another factor in figuring costs involves how you spend your time at home. If you use one room for long periods, a portable heater will keep you warm while allowing you to turn down the thermostat on your furnace 5° to 10°F. But if you're in one room while your kids are playing in another, you'll need to run two heaters or keep the thermostat at 68°F—neither of which will produce savings.

To determine the cost of running your portable heater, simply multiply the wattage of the unit by the cost of electricity in your area (cents per kWh; you'll find it on your electric bill) by the daily hours of use: (Wattage / 1000) x rate x hours used = Cost.

For the bigger picture, contact your local utility company and tell the customer service representative how much you plan to turn down your thermostat. "Most utilities have consumer helplines that can run the numbers for you," says Nelson.

Portable space heater at home iStock

Types of Space Heaters


Despite differences in heat delivery, all-electric heaters operate at a maximum of 1,500 watts that produce about 5,120 Btu (1 Btu is equal to the amount of heat produced by burning a wooden kitchen match). According to Nelson, "You can keep a medium-size room comfortable with 5,100 Btu with the wall thermostat set at 55° F." Electric space heaters fall into two categories, each of which shines in different circumstances.


Radiant heaters ($30 to $100) generate infrared radiation to quickly heat people or objects within the beam. Because they provide focused heat rather than warm the whole room, radiant heaters are a good choice for the garage, workshop, or in front of your favorite reading chair. For wider coverage, look for models with parabolic reflectors or small fans (called "fan-forced") to distribute the heat.

Although radiant heaters make you feel toasty, you lose their benefit quickly if you're moving around (out of the beam) or when the unit cycles off. Another disadvantage: Despite a protective grille and surrounding case, these heaters can get red-hot. In use, the radiant element can reach temperatures of 800° to 1500° F. This means that the case can become very hot, too, which makes it well worth choosing a model with a warning light that indicates when the case is too hot to touch.


These heaters ($15 to $100) work by warming the air. Although they take a little longer to make you feel warm, convective heaters generally do a better job. Unlike radiant units, some of the better convective heaters feature electronic temperature controls that can adjust heat output to maintain an even temperature, instead of simply cycling on and off.

Convective heaters can be divided into two subgroups: fan-assisted and fanless. Fan-assisted heaters rely on a ceramic or metal-wire heating element. Sam Pelonis, president of Pelonis Heating Products in Malvern, Pennsylvania, recommends fan-assisted ceramic heaters because of their lower operating temperature. "Ceramic elements gradually cut off the current as the temperature nears 380° F, which is less than the ignition point of paper," he says. Another advantage is portability. Ceramic heaters are the smallest portable heaters, which makes them easy to carry from room to room.

Another type of fan-assisted convective heater uses wire-type elements. These "heater fans" have their own advantages, according to Craig Plank, vice president of marketing for Vornado Air Circulation Systems in Andover, Kansas. "Wire-type elements allow better air circulation, which means you can heat a room more quickly." He also points out that unlike radiant units, the fan keeps elements from getting red-hot, which keeps the case cool to the touch.

More Considerations

When shopping for either type, look for a unit that features tip-over protection, which turns off the heater the instant it gets knocked over. Thermal shutoff switches found on most portable heaters will turn off a heater that's tipped on its face, but there's a chance the floor covering will be scorched first.

For silent, even heating, your best bet is a fanless, radiator-type heater ($40 to $100). These oil- or water-filled units resemble, and work much like, old-fashioned radiators. An element heats the fluid contained in a metal case, which in turn heats the room by using natural convective currents. Even when the heater cycles off, the heat stored in the body of the heater will continue to keep you warm.

Lamb frequently recommends oil-filled heaters. "Radiator-type heaters take longer to heat up, but there's no red-hot element or annoying fan." Lamb points out that some radiators have timers so you can "preheat" a room, for example, setting the heater to start a half hour before you wake up.

Portable heater at home iStock

Using Heaters Safely

A UL sticker means a heater has met safety guidelines set by Underwriters Laboratories. But despite that assurance, accidents can happen. "Like any electrical appliance, using your heater inappropriately can still put you or your home at risk," says Jim Novak, a senior product engineer at UL. To avoid the most common heater-related accidents, follow these simple safety tips:

Establish a safety zone.

Even with high-temperature shutoffs and protective grilles, Novak recommends establishing a 3-foot safety zone around a heater. In addition to placing your heater away from drapes and furniture, keep it out of traffic zones. "Kids and pets can get burned by poking at a hot element or brushing against a hot case," he says.

Don't use the heater to dry clothes or defrost pipes.

Clothes can get scorched before the thermal switch cuts out. Leaving a heater unattended in a basement/crawl space can also lead to fire.

Most extension cords are not designed to handle 1,500 watts.

If you must use a cord, make sure it's rated for 1,875 watts. A 9-foot cord using 14-gauge wire, for instance, is rated for 1,875 watts.

Water and electricity don't mix.

To date, only one space heater is approved for bathroom use. The Holmes HFH-430BR features a GFCI plug that shuts off the heater at the first sign of electrical leakage.

Space Heaters, Unplugged

Electric space heaters are tough to beat in terms of cost and convenience, but if you're looking for more than 5,120 Btu or want a way to heat your home if there's a power outage, two other options to consider are portable kerosene and gas heaters. These choices, however, have to be made carefully since both types of heaters use active combustion, with all the dangers that implies.

Kerosene heaters aren't as popular as they were back in the 1980s, but more than 5 million of them are still in use, according to the Consumer Product Safety Commission. Kerosene heaters are inexpensive (prices start at $100), don't require electricity, and provide a lot of heat (13,000 to 17,000 Btu).

However, there are several disadvantages. In addition to being a fire hazard, kerosene heaters consume oxygen and produce dangerous gases such as carbon monoxide and nitrogen dioxide. Although emissions are carefully regulated, small amounts can affect children and adults with preexisting respiratory problems. What's more, burning 1 gallon of kerosene produces 1 gallon of water vapor, which can create mold- and mildew-related problems, particularly in tight homes.

Still, kerosene is a safe temporary heat solution, provided you follow all of the manufacturer's safety guidelines. Don Grob, managing engineer at UL, says there are two primary safety concerns. The first is to maintain adequate ventilation. The rule is 1 square inch of window opening per 1,000 Btu. For example, if you're running a heater rated at 20,000 Btu, keep a 24-inch-wide window open about an inch. The second primary concern is to keep kerosene in its own storage container. "Homeowners sometimes use old gas cans for kerosene," he says. "It only takes a small amount of gas to create a major fire hazard."

Grob also recommends buying a new unit. "Since the '80s, kerosene heaters have lower emissions, better protective grilles, and low-wick shutoffs," he says. Newer heaters, like Kero-Sun's Double Clean 90, use a dual burn chamber to reduce emissions.

The newest entry into the portable heater category is fueled by propane gas; it's called the Portable Buddy. Certified by the American Gas Association, this portable heater provides 4,000 or 9,000 Btu and runs for three to six hours on its 1-gallon tank of propane. It also has a low-oxygen sensor that shuts the unit off if ventilation is inadequate.

There are a lot of different models to choose from. Most are safe when operated correctly, so use common sense. As for the savings, that depends on how and where you use the heater. But a good heater will transform a cold and drafty room into a comfortable and inviting one.