Research has shown that more than half of the energy used in the average home goes toward making its inhabitants comfortable. “Heating and cooling account for about 56 percent of the energy use in a typical U.S. home, making it the largest energy expense for most homes,” says the Energy Efficiency & Renewable Energy Office at the DOE. With the average homeowner spending about $1,500 a year on energy bills, it adds up to a significant amount of money.

Because conditioning a house represents the lion’s share of energy expenses, it is crucial that heating, ventilating, and air-conditioning (HVAC) systems be as energy efficient as possible. Fortunately, manufacturers have made amazing progress in the development of high-efficiency heat pumps and air-conditioning units.

The minimum SEER rating allowed for an air conditioner today is 13, for example, but manufacturers are able to produce units that go much higher.

Goodman Manufacturing Co. in Houston says its DSZC heat pump can be ordered in SEER ratings up to 18. Indianapolis-based Carrier offers a two-stage Infinity Series central air-conditioner line that can achieve a SEER rating of 21. “When combined with the advanced Infinity System, it is our most energy-efficient traditional heating and cooling system, based on stringent ARI cost standards,” Carrier says.

Gas furnaces have gotten more efficient, too. Lewisburg, Tenn.–based International Comfort Products, maker of the Comfortmaker line of furnaces, says its new SoftSound product has an annual fuel utilization efficiency rating of up to 97 percent. The company says the unit can be paired with a high-efficiency ECM blower, which results in even better performance.

It’s clear that a good HVAC system is an important part of any energy-efficient house and is a key piece for home buyers who want lower utility bills. But it’s only half the story. Builders should always think about energy efficiency as a system in which air conditioning is only one part.

“A highly efficient system should work in concert with high-quality insulation, water heater, windows, roofing, light fixtures, and energy-efficient appliances to ensure the greatest energy savings,” says Carrier. And the DOE states that home builders should make sure to perform proper air sealing and duct sealing, appropriately size their AC units, and include a programmable thermostat to ensure that HVAC systems function efficiently.

“A wide variety of technologies are available for heating and cooling your home, and they achieve a wide range of efficiencies in converting their energy sources into useful heat or cool air for your home,” the agency says. But for best results, builders should consult with building scientists to understand how components work together to determine the right solution based on the style of home and climate in which it’s being built.