As winter approaches, many homeowners shift their focus from cooling to heating, often forgetting that their air conditioning system—especially in homes with heat pump systems—plays a critical role even in colder months. But with changing seasons, a common question emerges: what temperature should AC be set at in winter? If you’re using a standard AC unit, it’s typically turned off, but if your HVAC system includes a heat pump or reversible air conditioning, maintaining the right temperature becomes essential for efficiency, comfort, and reducing energy bills.
This comprehensive article walks you through everything you need to know about setting the appropriate temperature for your air conditioning (or heat pump) system during winter. We’ll explore expert recommendations, energy-saving tips, the science behind comfort, and practical strategies to keep your home cozy without sacrificing efficiency.
Understanding Your Winter HVAC System
Before diving into temperature settings, it’s helpful to understand how your AC or HVAC system functions in winter. Many people assume air conditioners are only for cooling, but the reality is more nuanced—especially in modern homes.
The Role of Heat Pumps in Winter
Heat pumps are a popular alternative to traditional furnaces, particularly in mild to moderate winter climates. They work by reversing the refrigeration cycle: instead of removing heat from indoors and releasing it outside (as in summer), they extract heat from the outdoor air and transfer it inside, warming your home.
Yes, even in cold weather, outdoor air contains some heat—in fact, heat pumps can function efficiently at temperatures as low as 30–40°F (around -1°C to 4°C), depending on the model. Some advanced heat pumps with supplemental heating elements or dual fuel systems can operate effectively even in single-digit temperatures.
Traditional Air Conditioners in Winter: Off or Unused
For homes with standard central air conditioning or window units, the AC unit is typically not used during winter unless there’s an unexpected warm spell. These units only cool and dehumidify, so setting them to a lower temperature in winter doesn’t generate heat—it simply blows cold air, which is impractical and energy-wasting when the furnace or heating system is active.
So, when people ask, “What temperature should AC be set at in winter?” they’re usually referring to their heat pump or thermostat settings, not the traditional cooling function.
Recommended Winter Temperature Settings for HVAC Systems
When your HVAC system includes heating capabilities (via a heat pump or auxiliary heater), your thermostat becomes the control center for winter comfort. The Department of Energy (DOE), American Council for an Energy-Efficient Economy (ACEEE), and leading HVAC experts agree on general guidelines for thermostat settings in winter.
Optimal Thermostat Setting: 68°F (20°C)
The recommended indoor temperature during winter is 68°F (20°C) when you’re at home and awake. This temperature strikes a balance between comfort and energy efficiency. According to the DOE, setting your thermostat to this level can help you save up to 10% on annual heating and cooling costs—especially when combined with lower nighttime or away settings.
While 68°F might feel slightly cool to some, it’s a scientifically backed sweet spot. It’s warm enough to prevent discomfort and shivering, yet cool enough to minimize the load on your system and reduce energy consumption.
Lower Settings When Asleep or Away
To further increase savings:
- When sleeping: Lower the thermostat to 62–65°F (16–18°C). Your body naturally cools during sleep, and wearing warm pajamas or using extra blankets can maintain comfort.
- When away from home: Reduce the temperature to about 60°F (15.5°C), especially if you’re gone for more than four hours. Modern heat pumps handle gradual temperature changes well and will efficiently bring the home back to a comfortable level upon your return.
Smart Thermostats Make Adjusting Easier
Programmable and smart thermostats (like Nest, Ecobee, or Honeywell Home) allow you to schedule temperature changes automatically. You can program a morning warm-up, lower temperatures during work hours, and a gentle rise before you return. Studies show that homes using smart thermostats save an average of 8–12% on heating costs annually.
Climate-Specific Considerations
The ideal winter thermostat setting also depends on where you live. What works in Florida may not be suitable for Minnesota.
Mild Winter Climates (e.g., Southern U.S.)
In regions like California, Texas, or Georgia, winter temperatures rarely dip below freezing. Heat pumps operate efficiently, and outdoor air retains enough thermal energy to transfer indoors. In these areas, setting your thermostat at 68°F during the day is ideal. You may not need to go below 65°F at night since drastic temperature swings aren’t necessary.
Harsh Winter Climates (e.g., Northern U.S., Canada)
In colder areas such as Michigan, Wisconsin, or New England, heat pumps may struggle when temperatures fall below 30°F. Homes often use:
- Auxiliary (backup) heating (usually electric resistance coils), which kicks in when the heat pump can’t keep up.
- Dual fuel systems, combining a heat pump with a gas furnace. The furnace handles extreme cold, while the heat pump covers milder temperatures efficiently.
In these climates, keeping your thermostat stable at 68°F during occupancy is still effective. However, frequent extreme temperature adjustments can over-rely on auxiliary heat, which uses more electricity. Avoid setting the thermostat too high (like 75°F+) in hopes of feeling warmer quickly—this doesn’t speed up heating and wastes energy.
Regional Comparison Table: Average Winter Thermostat Settings
| Region | Avg. Winter High (°F) | Recommended Indoor Temp (°F) | HVAC System Tips |
|---|---|---|---|
| South (e.g., Florida, Arizona) | 65–75 | 68–70 | Heat pump runs efficiently; little need for auxiliary heat |
| Mid-Atlantic (e.g., Virginia, Pennsylvania) | 35–50 | 68 | Use heat pump with scheduled setbacks for savings |
| North (e.g., Minnesota, Maine) | 15–30 | 67–68 | Prefer dual fuel systems; minimize auxiliary heat use |
Common Myths About Winter AC and Heating Temperatures
Misinformation can lead to discomfort and higher energy bills. Let’s debunk some widely held myths.
Myth 1: Turning the Heat Up Higher Warms the House Faster
This is false. HVAC systems heat at a fixed rate—whether you set the thermostat to 70°F or 80°F, it warms the space at the same speed. Setting it higher only risks overshooting the desired temperature and wasting energy. Set your thermostat to your target temperature and let the system do its job.
Myth 2: Leaving the Heat On All Day Saves Energy
Some believe that constantly keeping the heat on avoids the “energy spike” of restarting the system. However, research from the ACEEE shows that allowing temperatures to drop during unoccupied periods saves energy. Modern systems are designed to ramp up efficiently, and the energy saved by running less during low-demand times outweighs the cost of reheating.
Myth 3: Heat Pumps Don’t Work in Cold Weather
While older models struggled in freezing conditions, modern inverter-driven heat pumps can operate effectively down to -15°F in some cases. With features like variable-speed compressors, enhanced defrost cycles, and supplemental heating, these systems are viable even in colder regions.
Health and Comfort: Why Temperature Matters
Temperature isn’t just about energy bills—it impacts your well-being.
Indoor Air Quality and Humidity
Dry air is common in winter due to heating, leading to issues like dry skin, irritated sinuses, and increased static. Maintaining a moderate temperature (like 68°F) helps preserve indoor humidity levels when paired with a humidifier. Ideal indoor humidity in winter is 30–50%.
Too high a temperature can exacerbate dryness, while too low a setting can make the air feel clammy and uncomfortable.
Health Implications of Indoor Temperatures
The Environmental Protection Agency (EPA) warns that consistently cold indoor temperatures (below 64°F) can increase the risk of respiratory issues, especially for the elderly, children, and those with chronic conditions.
On the other hand, overheated homes (75°F+) may lead to dehydration, disrupted sleep, and increased allergen circulation. Keeping your home around 68°F supports respiratory health, better sleep, and stress reduction.
Energy Efficiency and Cost Savings
Your thermostat setting directly influences your energy bills. Here’s how to strike a balance.
The 1°F Rule
For every degree you lower your thermostat for eight hours (e.g., during sleep), you can save about 1% on your heating bill. Lowering the temperature from 72°F to 68°F can mean a 4% savings. When multiplied over months, this adds up significantly.
Smart Zoning and Room-Specific Control
Modern HVAC systems allow zoning—controlling temperature per room. If you spend most of your time in the living room, keep that area at 68°F while letting guest rooms cool to 62°F. This reduces energy use without sacrificing comfort.
Portable space heaters can also supplement central heating but should be used cautiously. They’re less efficient than central systems and pose fire risks if misused.
Insulation and Sealing: The Foundation of Efficiency
No thermostat setting compensates for poor insulation. Drafts around windows, doors, and attics can significantly increase heating demands. According to the U.S. Department of Energy:
- Heating and cooling account for nearly half (48%) of home energy use.
- Proper insulation can reduce heating needs by up to 20%.
Seal air leaks and add insulation to attics, walls, and basements. Weather stripping and thermal curtains also help maintain indoor temperatures.
How Humidity Affects Perceived Temperature
A home at 68°F with 50% relative humidity feels warmer than the same temperature at 20% humidity. This phenomenon is known as “relative warmth” or “thermal comfort”.
Low humidity in winter can make 68°F feel chilly, prompting you to turn up the heat. Instead of increasing the thermostat, consider:
- Using a whole-house or room humidifier.
- Boiling water on the stove (safely monitored).
- Placing water basins near heating vents.
Adding moisture to the air can make lower temperatures feel cozier, reducing the temptation to raise the thermostat.
Practical Tips for Winter Thermostat Management
Use a Programmable or Smart Thermostat
Set schedules based on your routine:
- Warm up the house to 68°F about 30 minutes before waking.
- Drop to 64°F during work/school hours.
- Raise to 68°F again in the evening.
- Cool to 62–65°F at bedtime.
Smart thermostats learn your habits and adjust automatically. They can also monitor humidity, occupancy, and outdoor conditions.
Reverse Ceiling Fans
Did you know your ceiling fan can help in winter? Run it in **clockwise direction at a low speed** to gently push warm air (which rises) back down into the living space. This can make the room feel warmer, allowing you to set the thermostat slightly lower.
Regular HVAC Maintenance
A poorly maintained system works harder and less efficiently. Schedule annual check-ups to:
- Replace or clean air filters (clogged filters reduce airflow by up to 15%).
- Inspect the heat pump coils and defrost cycle.
- Check thermostat calibration.
- Clean ducts if needed.
Well-maintained systems can improve efficiency by 15–20%.
When to Seek Professional HVAC Advice
While setting your thermostat to 68°F is a great starting point, individual homes vary. Factors like home size, layout, insulation, and HVAC age impact ideal settings.
Consider consulting an HVAC professional if:
- Your home never reaches the set temperature.
- The system frequently switches to emergency heat.
- Some rooms are consistently colder or hotter than others.
- Energy bills are spiking despite consistent usage.
They can conduct a home energy audit and recommend system upgrades, zoning solutions, or thermostat recalibration.
Conclusion: Balancing Comfort, Health, and Savings
So, what temperature should AC be set at in winter? If you’re using a heat pump or reversible system, the optimal indoor temperature is 68°F (20°C) when you’re home and awake. Lower it to 62–65°F when sleeping or away to save energy. Avoid drastic temperature swings and use smart thermostats to automate the process.
This balance enhances comfort, supports healthy indoor air quality, and minimizes your carbon footprint and energy bills. Remember, efficiency starts with habits—layer up with cozy clothing, seal drafts, maintain your system, and embrace moderate temperatures.
Winter doesn’t have to mean sky-high heating bills or a freezing home. With the right thermostat strategy, you can enjoy a warm, welcoming environment all season long—efficiently and economically.
What is the ideal temperature to set the AC in winter?
The ideal temperature to set your air conditioning in winter is not applicable because air conditioning systems are primarily designed for cooling during warmer months. In winter, most homes rely on heating systems, such as furnaces or heat pumps, to maintain comfort. However, if you’re using a heat pump—which acts as both a heater and cooler—you should set it to heat mode and aim for a thermostat setting between 68°F and 72°F (20°C to 22°C) when home and awake. This range offers an optimal balance between comfort and energy efficiency.
Setting your thermostat too high can lead to excessive energy use and increased utility bills. Experts recommend lowering the temperature by 7–10 degrees when you’re asleep or away from home for eight hours, which can save up to 10% on heating costs annually. Using a programmable or smart thermostat can automate these adjustments, ensuring comfort when needed and savings when not. Always ensure your heat pump’s auxiliary or emergency heat functions aren’t unnecessarily engaged, as this drastically increases energy consumption.
Can I use my air conditioner during the winter months?
Typically, you do not use a traditional air conditioner during winter because it is designed to remove heat from indoor air to cool your home. Running a standard AC unit in cold weather can damage the system, as low outdoor temperatures may cause the refrigerant to operate inefficiently or even freeze components. Most central air conditioning systems should remain off during winter unless specifically equipped and designed for dual functionality.
However, some HVAC systems, such as reversible heat pumps, can effectively function in winter by extracting heat from the outside air and transferring it indoors. These systems are not traditional AC units but are often paired with them in modern homes. If you have a heat pump, it’s perfectly safe and effective to use it in winter. Always consult your system’s manual or an HVAC professional to determine whether your unit is designed to operate in cold weather.
Why does my heat pump run in cold weather but my AC does not?
Heat pumps are engineered differently than standard air conditioning units. They use a reversing valve that allows the system to switch between heating and cooling modes. In winter, the heat pump extracts heat energy from the outside air—yes, even in cold temperatures—and transfers it inside to warm your home. This process is efficient down to around 30°F to 40°F (-1°C to 4°C), depending on the model, making it a viable option in moderate climates.
In contrast, traditional air conditioners lack this reversing capability and are only built to cool. Operating them in cold weather can lead to compressor failure, refrigerant issues, and frozen coils. Additionally, using the cooling function in winter would lower indoor temperatures when heating is needed, increasing energy use and discomfort. That’s why AC units are typically turned off during colder months, while heat pumps continue to function efficiently as a heating source.
How can I save energy when heating in winter?
One of the most effective ways to save energy during winter is to set your thermostat to 68°F (20°C) when you’re home and awake, then lower it when you’re asleep or away. Reducing the temperature by 7 to 10 degrees for at least eight hours a day can result in significant savings—up to 10% per year on your heating bill. Using a programmable or smart thermostat helps automate these adjustments without sacrificing comfort, making it easier to maintain efficient temperature settings.
Beyond thermostat management, sealing air leaks around windows and doors, adding insulation, and maintaining your heating system also contribute to energy savings. Regularly changing air filters ensures your system runs efficiently, while ceiling fans set to rotate clockwise at low speed can help circulate warm air trapped near the ceiling. These combined strategies reduce strain on your HVAC system and help maintain a consistent indoor temperature.
Should I turn off my AC completely in winter?
Yes, if you have a separate air conditioning unit or a traditional split HVAC system, it’s generally best to turn the AC off during winter months. Since cooling is not needed, leaving it inactive prevents unnecessary wear and potential damage from running the system in cold conditions. You can switch your thermostat to “heat” mode to activate your furnace or heat pump instead, ensuring your home remains warm when necessary.
However, before shutting down the system, it’s wise to schedule a fall maintenance check to ensure both heating and cooling systems are in good working order. Leaving the thermostat powered and using a programmable schedule allows you to maintain ideal heating settings without interference from AC functions. Periodic short tests of the AC during milder winter days can also help ensure it’s ready for summer, but continuous operation in winter should be avoided.
What is the best thermostat setting for sleeping in winter?
The best thermostat setting for sleeping in winter is approximately 62°F to 66°F (16°C to 19°C). A slightly cooler sleeping environment promotes better sleep quality by helping your body lower its core temperature naturally, which is part of the sleep onset process. While this may seem chilly, using warm bedding, pajamas, and layered blankets can maintain comfort without overworking your heating system.
Maintaining a cooler bedroom temperature at night also contributes to energy savings. When you consistently lower the thermostat during sleeping hours, you reduce the overall heating load on your system. Smart thermostats can be programmed to return the temperature to a more comfortable level before you wake up, ensuring you rise to a cozy environment without manual adjustments. This balance supports restful sleep and long-term energy efficiency.
How does outdoor temperature affect heat pump efficiency in winter?
As outdoor temperatures drop, the efficiency of a standard air-source heat pump decreases because there is less ambient heat available to extract from the air. Most heat pumps operate efficiently down to about 30°F to 40°F (-1°C to 4°C). Below this threshold, the system may struggle to meet heating demands and often activates auxiliary or “emergency” heat, which uses electric resistance heating and consumes significantly more energy.
To maintain efficiency in colder climates, consider upgrading to a cold-climate heat pump designed to function effectively at lower temperatures, sometimes as cold as -15°F (-26°C). These models use advanced compressors and refrigerants to extract heat efficiently even in freezing conditions. Supplementing your heat pump with other heating sources, like natural gas or radiant floor heating, can also improve comfort and cost-efficiency during extreme cold snaps.