Dual-fuel systems have become all the rage lately, primarily due to the increasing cost of fossil fuels. By pairing a fossil fuel furnace with an electric heat pump, manufacturers say the systems can often pay for themselves within a few years, while providing a higher level of comfort to homeowners and their families.

These systems do come with a price premium, as the cost of a heat pump is higher than that of an air conditioner. However, manufacturers state that the energy savings a consumer will achieve with a dual-fuel system versus a standard furnace and air conditioner combination will far outweigh the difference in cost between the systems.

COMFORT A FACTOR

In addition to saving on the utility bill, dual-fuel systems are often credited with providing better comfort than a traditional heating-cooling system. Nathan Floyd, product manager - heating, Carrier, noted that comfort is actually the biggest benefit of dual-fuel systems. “Anytime you have multiple stages of heat, comfort levels in the home should be improved. Our dual-fuel systems can offer from two-to five-stages of heat. By having multiple stages of heat, the system is trying to more closely match the heating needs of the space or home.”

Carrier has offered the Infinity Hybrid Heat® dual-fuel system since 2006. The company recommends that its dealers offer a best, better, good approach when selling Hybrid Heat systems. The “best” system pairs the 95-percent AFUE IdealComfort™ modulating gas furnace with an Infinity™ Series two-stage heat pump, which has SEERs up to 19. Matched with the Infinity Control, Floyd stated this system provides 3.5 times tighter temperature control than a single-stage system, eliminating sudden changes in indoor temperature.

Carrier’s latest furnace offering, the Performance™ Boost 90-percent gas furnace, can provide a SEER boost of up to 1.5 points to the outdoor unit, providing even greater energy savings for the homeowner. “Combining this furnace with any of our tiers of single-stage heat pumps gives the homeowner a cost-effective way to obtain a Hybrid Heat system,” said Floyd.

Trane also offers a dual-fuel system. Its highest efficiency EarthWise™ split system matches the Trane XL15i, 16i, and 19i heat pumps with the Trane XV95 furnace, which is rated up to 96.7-percent AFUE. The company says this combination allows customers to use less energy without giving up a single bit of comfort. The Trane XL16c packaged unit is also available in a dual-fuel option, and this configuration offers SEERs up to 16.6 and an 80-percent AFUE.

Comfort is definitely a concern for homeowners,” said Randy Scott, vice president of product systems management, Trane. “As a split system, the EarthWise heat pump cools and dehumidifies. During the spring and fall, the heat pump provides high-efficiency heating. When the temperature dips into the frigid zone, the XV 95 furnace provides gas heat for greater comfort. In areas where natural gas is not available, propane gas can be used for fuel.”

ALL ABOUT ENERGY SAVINGS

Even though comfort is important, saving energy is probably the main reason why consumers purchase dual-fuel systems. By having two sources of heating - electricity and fossil fuel - customers have the option to choose which source to use, depending on current energy prices. Manufacturers say this flexibility has led to higher sales of dual-fuel systems.

“Dual-fuel systems make sense in any market where the customer wants the ongoing flexibility to weigh the cost and comfort options of gas versus electricity,” said Mark King, product manager - residential cooling, Rheem.

“The actual savings is dependent on the local cost of gas and electricity. In colder climates, dual fuel is gaining momentum as a means of offsetting the rising cost of gas, by heating with electricity during the milder seasons.”

King added that while milder climates have been quick to accept dual fuel, there is a bias towards gas in the Northern regions. “Dual-fuel systems allow these regions to still feel the security of gas without eliminating the option of saving money by using a heat pump during the milder seasons,” he said.

All of Rheem’s electric heat pumps and gas furnaces are compatible with dual-fuel applications. The company’s heat pump line has efficiency levels of 13 through 17 SEER, and all heat pumps can be matched with the two-stage, ECM 80-percent furnace or with the Mod 90 (modulating 90, which features variable speed) furnace.

Jamie Byrne, vice president of sales, American Standard Heating & Air Conditioning, agrees that dual-fuel systems give customers greater control over energy costs, as the fuel choice can be determined by their comfort needs and according to annual fluctuations of energy prices. “Installing a Heritage Hybrid™ split system can deliver up to 68 percent energy savings over a comparable 10-year-old system and 37 percent savings compared to more recent systems. In addition, utility rebates are available in some markets, as well as the tax credits available through the Energy Policy Act of 2005.”

The top-of-the-line Heritage Hybrid Comfort System consists of a Freedom furnace with AFUE ratings up to 96.7 percent and up to three stages of gas heat combined with a Heritage® 16 or 18 SEER heat pump, which offers two-stage heating and cooling. The Freedom furnace and Heritage heat pump come with Comfort R technology, which minimizes short cycling and temperature swings. Also available are Heritage Hybrid packaged units, which have efficiencies up to 16 SEER.

Both systems utilize variable-speed blowers and two-stage heating and cooling. “Staged systems provide maximum comfort and even temperatures throughout the home by eliminating short cycling, cold spots, and temperature swings typical in single-stage systems,” said Byrne.

Some contractors may be concerned that dual-fuel systems are more complicated to install, but according to King, the advent of dual fuel-compatible thermostats has virtually eliminated the complexity of installing additional controls. “Outside of the controls component, the furnace, heat pump, indoor coil, and ducting system are really no different than what the contractor is used to seeing.”

Jeff Warther, product manager - heat pumps, Carrier, agreed, noting, “These systems are as easy to install as any gas furnace-compressor combination, and the service is the same as any gas furnace-compressor combination. When the Infinity Control is installed, there is a four wire hook-up and self-configuration. Once contractors point out the operating cost comparisons, homeowners can see the savings and payback opportunities.”

Both Trane and American Standard also have simplified installation with their communicating systems: Only two wires are required to connect the outdoor system with the control.

For contractors, easier installations are a big benefit. For consumers, though, it comes down to lower operating costs, and with the price of energy continuing to rise, it’s a sure bet that an increasing number of homeowners will be asking questions about how they can benefit from the installation of a dual-fuel system.

Publication date: 11/17/2008