Dual Is Better Than One

Twice the technology equals twice the efficiency: New dual fuel heating systems will take the guesswork out of choosing the most efficient way to heat your home this winter.

Story by Karen J. Bannan

It may be summer, but the utility companies are already thinking about colder weather. Today, major utility and fuel providers are readying advertising designed to grab their competition's customers. The ads will tout rising fuel prices and say their option is the most cost-effective one. But their efforts will be wasted on homeowners who have dual fuel systems.

Dual fuel systems, or in the case of heating manufacturer Carrier Corp.'s offering, Hybrid Heat, are designed to protect homeowner pocketbooks when either gas or electric rates rise. The technology, which was introduced in January, runs on both.

"A dual fuel system is an air comfort system consisting of a heat pump with a gas furnace versus a heat pump with auxiliary electric heat or a standard air conditioner with either electric or gas heat," explains Andrew Smith, owner of the Aire Serv franchise in Nederland, Texas. "When the heat demand in your home reaches a certain point, the system knows which fuel is more cost-effective and switches to that fuel source automatically."

What's Under the Hood
Dual fuel systems aren't completely new to the market. The units, which combine a heat pump with a gas-burning furnace, have been available in the past. In theory, they are wonderful. When it is hot out, homeowners can run the air conditioner, keeping their home cool. When the temperatures start to drop, they can flip over to the electric heat pump, which removes heat from air outside the home—copper tubes filled with refrigerant absorb heat from the air—and brings it into the house. If it gets too cold outside and there is scant heat in the air, the homeowner can run the gas-powered furnace.

The problem, says Richard Ciresi, owner of the Aire Serv franchise of Louisville, Kentucky, was figuring out when to switch the system from the electric heat pump to the furnace.

"Heat pumps become less and less efficient as the temperature drops," explains Ciresi. "A heat pump will heat your home and will run down to four or five degrees—some even down to zero—and still produce heat. However, they start losing efficiency somewhere around 28 to 32 degrees outside."

This meant that homeowners who owned some of these older dual fuel systems had to watch the thermometer or they would end up paying too much in electricity costs or using too much gas unnecessarily. (In general, however, heat pumps were more cost-effective since they didn't generate heat by combustion like a furnace, explains Smith.)

"In the past, you had to manually figure out which one you wanted to use. They weren't fully automated. They were controlled by a simplified thermostat," he says.

The new units let you input your fuel costs—how much you pay for electricity per kilowatt hour, and how much your natural gas costs per thousand cubic feet (mcf). Once the data is entered, these new units will automatically switch back and forth between electricity and gas depending on heating usage, says Smith.

"This is an out-of-sight, out-of-mind system," he says. "You don't have to make the decision on whether gas or electric is going to be the best buy today or in the long-run. No matter what happens, you're protected."

The thermostat only needs updating when your fuel costs rise and fall, and can be programmed by the consumer, although the person who handles your system maintenance is capable and willing to program it for you, too.

Warmed by Savings
Not surprisingly, the biggest reward of switching to a dual fuel system is a financial one. Although a dual fuel system will cost between 10 and 40 percent more than a standard air conditioner and furnace, you can save 40 to 50 percent on your winter heating costs over time, says Ciresi of Aire Serv. "A standard dual fuel heat pump can be 180 percent more efficient than straight electric heat; a high-efficiency dual fuel heat pump can be 200 percent more efficient," he says. "A heat pump is going to cost you more than a regular air conditioner, but in the winter you'll save money by also producing heat." And with natural gas prices continuing to rise, according to the Energy Information Administration, cost savings will continue to rise. Keep in mind, though, that savings vary depending on the outside temperature, the cost of utilities and gas, and how warm you like to keep your home.

"Of course, people who live in really cold climates wouldn't consider a dual fuel system," says Ciresi. Neither should people with a perfectly working air conditioning unit that is less than 10 years old. That said, if you are looking to replace an aging system, there are some things you should consider, say experts.

Consumers who purchase a higher-efficiency model can benefit immediately, because the federal government is offering rebates on ENERGY STAR equipment.

There are several considerations outside of cost. In fact, the choice between natural gas and electric isn't always a cost-based one, says Ciresi. "Sometimes it has to do with comfort," he explains. "Some people prefer warmer discharge temperatures when it gets really cold out."

An electric-powered heat pump discharges air heated to between 100 and 105 degrees. Meanwhile, on average, a gas-powered furnace discharges air that's about 140 degrees. While they both heat a home equally as well, homeowners using a gas-powered furnace might warm the toes and nose more noticeably.

A dual system can also provide peace of mind for those consumers who use it to heat a vacation home, for example. Homeowners don't have to worry about running out of gas or leaving a gas-powered system unattended for months on end. They can set the system to run on electricity only, and switch over to gas once they return. The best part: You don't have to leave your home to switch from gas to electric heat, explains Ciresi.

"All you have to do," he says, "is push a button on the thermostat."

Temperature Tips

Heat pumps become less and less efficient as the temperature drops. The thermostat only needs updating when your fuel costs rise and fall, and can be programmed by the consumer. Consumers who purchase a higher-efficiency model can benefit immediately, because the federal government is offering rebates on ENERGY STAR equipment.