Whether you live in cold or hot climates (or both), efficient heating & air conditioning can reduce expensive home costs through lower energy consumption. Therefore, it is a great place to improve! However, home energy efficiency can likewise reduce costs through home sealing (and in particular, duct sealing), insulation, and other efficiency ideas.
Your Choices
| Efficient Heating & Air Conditioning Options and Links | Explanation |
| Understanding Furnaces | Learning where your furnace may be now |
| Upgrade to a Heat Pump for Efficient Heat & Air Conditioning | Currently best option: one product cools and heats efficiently |
| Air Conditioning: Improve Home Efficiency First | |
| Replacing an Old Air Conditioner | |
| Select an Alternative Cooling System | |
| Parent Link: Ways to Save Home Energy | Other actions you can take to increase energy efficiency |
| Parent Link: Ways to Save Electricity | Other actions you can take to reduce electrical costs |
Understanding Furnaces
Furnaces are rated for efficient heating via the Annual Fuel Utilization Efficiency (AFUE) metric, which measures how much fuel actually turns into heat. The current minimum efficiency in the U.S. is 80%, or 75% for mobile homes. High efficiency furnaces rate at or above 90% efficiency (Holladay, 2017). In other words, if you change from a 80% efficient furnace to a 98% efficient furnace, you will reduce fuel bills by nearly 20% – except that your savings are likely to be higher since old technologies deteriorate with time and newer, more efficient technologies tend to use less electricity. However, consider heat pumps for much greater savings.
Furnaces also vary in the speed options of the blower (Holladay, 2017):
- Single stage: single blower speed, turns on and off only.
- Two-stage: operates commonly at a lower speed (Btu) except on cold days.
- Modulating gas: provides a variable fuel rate for continual but varied heat flow.
Whether or not you choose to upgrade, be sure to seal accessible duct seams. It is estimated that 5.3% of air flow leaks at the furnace, and up to 75% of high-pressure heat or air conditioned air may escape before it reaches your room vents (Holladay, 2017). See home (and duct) sealing for more details.
Upgrade to a Heat Pump for Efficient Heat & Air Conditioning
Older furnaces may run to 70-ish% efficient; increasing to 80 and 90% efficient with condenser (Amann et al., 2012). The most efficient furnaces operate at 98% efficient and gas boilers 90% efficient. However, heat pumps operate to 300% efficiency (Quaglia, 2025). Systems do require an air duct system for air distribution.
Heating or Cooling: An air-source heat pump operates similar to a refrigerator in that it removes hot air from within the appliance. A heat pump can remove heat from the air, thereby cooling it and replacing a central air conditioning system. In addition, it can remove coolness from the air, thereby warming it and replacing a furnace. These are rated using a Heating System Performance Factor (HSPF). An HSPF rating of 10 delivers 3 kWh of heat for 1 kWh, providing an efficiency of 290% (Harley, 2012). Ground-source heat pumps are also available, but less common.
Test Results: Heat pumps originally operated well down to 40-45° Fahrenheit (F), but not below 30° unless paired with a regular furnace. However, with today’s advanced technologies, they can operate in cold winters. Monitoring 550 heat pumps installed in North America, China and central Europe provided an average efficiency of 2.74 heat units for every energy unit, even while operating between 14 to 41 degrees F or 5-10 Celsius. Tests in Finland, Minnesota and Alaska showed heat pump efficiency rated between 1.5 and 2 heat units per energy unit, even in cold winters ranging between -22 to 14 degrees F (Quaglia, 2025).
Air Conditioning: Improve Home Efficiency First
Increases in solar and other heat arise from solar radiation (sun through windows, skylight, roof), internal home gains (through cooking, showers, people, appliances) and air leakage (ducts and house leakages) (Harley, 2012). It is best to reduce the need for air conditioning first, addressing the three sources of heat gain: sealing ducts and leaks, improving attic and wall insulation, using a ceiling fan, installing a light-colored and solar-reflective roof, upgrading windows, and/or shading externally (best) through awnings, shutters, trees, trellises; and/or internally, through cellular or lighter shades.
In addition to cooling, air conditioners also dehumidify air for comfort and air quality. Using exhaust fans for cooking and baths/showers helps to remove humidity caused by internal gains.
Replacing an Old Air Conditioner
If an air conditioner is 20 years old or older, a new device will be cost-effective. It is best to buy as efficient as possible. Central air conditioners are rated using Seasonal Energy Efficiency Rating (SEER), which measures British thermal units (Btu) per hour of cooling output per watt input (Harley, 2012). Room air conditioners are rated with Energy Efficiency Ratio (EER), which contrasts slightly lower than SEER (Amann et al., 2012). Higher (S)EER values are more efficient, but recommended standards differ between northern and southern climates.
Select an Alternative Cooling System
Other cooling systems include (Amann et al., 2012)(Harley, 2012):
- A (ductless) minisplit heat pump has a high purchase price to cool 1-2 rooms, but may cost 1/3 to ½ as much in operation.
- Evaporative coolers are useful in hot, dry areas such as the southwest U.S. They can lower temperatures by 30° by sending outside air through moist pads generating evaporation of cooler air, via fans.
- Economizers are sophisticated air conditioners that select air from outside when outside is cooler and dryer than indoors. Of course, this can be done manually through opening and closing windows at opportune times.
- A whole house exhaust fan can cool a house in minutes, when it is cooler outside by blowing air into an unconditioned attic or outside.
References
- Amann, Jennifer Thorne, Wilson, Alex, and Ackerly, Katie (2012) Consumer Guide to Home Energy Savings, 10th edition. New Society Publishers, Gabriola Island, BC Canada.
- Harley, Bruce (2012) Insulate and Weatherize for Energy Efficiency at Home. The Taunton Press, Newtown CT.
- Holladay, Martin (2017) Musings of an Energy Nerd: Toward an Energy Efficient Home, TheTaunton Press, Newton CT.
- Quaglia, Sofia (2025) Do Heat Pumps Work When It Gets Really Cold? NY Times, Oct 15, 2025, updated Oct. 22, 2025. From: https://www.nytimes.com/2025/10/15/climate/heat-pumps-cold.html.