Heat pumps transfer heat from the outside air into your home, making them efficient and cost-effective heating and cooling methods. However, air-source heat pump output will vary depending on the outdoor temperature and your thermostat’s settings.
So, how hot should the air be from a heat pump? The average temperature output of a heat pump is 85°F to 92°F in heat mode without auxiliary heat. Typically, a heat pump will produce a temperature differential of 15-20°F warmer than the current air temperature in heat mode. The air temperature from a heat pump can vary with the age and condition of your heat pump.
The average heat output can be 85-92°F; however, how warm the output from your heat pump will be is determined by several factors, including age and condition of the heat pump. Newer heat pumps with R410a refrigerants can extract more heat from the outside air, which improves output.
The table below compares the output from a heat pump compared to electric and gas furnaces.
|Heat Source Output Ranges||Output Temperature|
|Heat Pump without Aux Heat:||85-92°F|
|Heat Pump with Aux Heat:||105-125°F|
If your heat pump is not producing hot air, see our article 16 Reasons Your Heat Pump Doesn’t Blow Hot Air.
At What Temperature Should AUX Heating Come On?
Heat pumps use refrigerants and heat exchangers to extract heat from the outside air, even in cold weather. However, below 30 degrees, they lose a lot of their efficiency and need assistance to keep up with demand from the thermostat.
So, what temperature will Aux heat turn on? The heat pump will engage the aux heat automatically when the outside air temperature is below 30°F. The heat pump will also use emergency auxiliary heat in heat mode if the thermostat raises the temperature more the 2°F.
For example, if the outside temperature is 40°F, and the indoor thermostat reads 67°F, setting the thermostat is 74°F would engage the aux heat to assist in meeting the desired temperature of 74°F as quickly as possible. The heat pump will use emergency heat to help achieve a comfortable temperature as quickly as possible in heating mode.
Because heat pumps use the air from outside, they often require help heating your house when the weather is freezing. As a result of this trait, AUX heat kicks on in low temperatures. To understand the best temperature for AUX heat, you must first know how it works.
What Is AUX Heat?
Heat pumps extract heat from the outside air to heat your house, which works well in warmer months but is hard to do in freezing weather. Unfortunately, when the air is freezing, the heat extracted from the outdoor air isn’t sufficient to heat your home without some assistance. The air brought in by the heat pump is less than the heat loss from the building. In this case, you need AUX heat to meet the demand.
Aux heat (also known as an auxiliary, supplemental, or emergency heat source) can be a gas furnace or electric heat strip backup that turns on to assist the heat pump in heating the house when the temperature drops below 30°F.
Aux heat assists the compression heat from the heat pump to keep you warm in cold weather.
It is essential to understand that auxiliary heat is not used. You can go months in the summer without using your AUX heat and relying on your heat pump.
Depending on where you live, Auxiliary heat is generally used in the winter months and late fall when it is cold. People in the North will use their AUX heat more often, but you can often avoid it if you live in the South, where the climate is warmer.
Finally, Auxiliary heat is used with your heat pump, distinguishing it from emergency heat.
Auxiliary Heat, Backup Heat, and Emergency Heat: Is There a Difference?
Many people confuse auxiliary heat, backup heat, and emergency heat. There is no real difference between the three, and it references the same components inside your heat pump. Auxiliary heat, backup heating, and emergency heat use the same heat strips or gas furnace to supplement the heat pump to heat your home.
The difference between Aux heat and Emergency Heat is simple: The emergency heat setting on the thermostat allows you to bypass the heat pump and run off the electric heat strips only. Aux heat combines heat strips and the heat pump to heat the house that occurs automatically without you doing anything.
Furthermore, Auxiliary heat will automatically turn on at a certain temperature. Emergency heat should be manually turned on by the homeowner if there is a problem with the heat pump. If emergency heat turns on automatically, your heat pump may be damaged or broken.
Emergency Heat Explained
Emergency heat can be turned on when your heat pump is not working or is damaged. This setting causes your thermostat and heat system to automatically get heat from your second stage heat source, which may be a furnace or electric heat strip. Heat strips are located inside the indoor air handler and heat the air before entering the ductwork to be distributed through the house.
When emergency heat is used, your heat pump is not. Overall, emergency heat is made to warm your house if there is a problem with your heat pump or if it cannot adequately heat your home.
What Temperature should AUX Heat Come On?
Your auxiliary heat should turn on when the outdoor temps are near 30° Fahrenheit and below. This temperature is when your air-source heat pump struggles to obtain enough heat from the outside air to warm your house. Therefore, when the temperature is below 30 degrees, AUX heat is needed to supplement your heat pump.
When this 30-degree temperature is reached, your AUX heat should turn on automatically- you do not need to operate it manually. If your auxiliary heat is on when the weather is warm, you should contact a professional to help you find the problem.
What Temperature Should I Set My Heat Pump in the Winter?
When it comes to operating your thermostat settings during the winter, we encourage homeowners to set the heat as low as they can stand it. This will be different for everyone.
Ideally, the most energy-efficient setting during the winter is to set the temperature to 68°F and leave the thermostat alone. If you need it warmer, raise the temperature by 1° until you find your ideal comfort setting.
Are you considering a dual fuel heat pump? See our article Are Dual Fuel Heat Pumps Worth It? What You Need to Know.
As I have discussed, air-source heat pumps operate by drawing energy from their surroundings and raising the temperature for heating or lowering it for cooling. The more significant the difference between the outdoor and indoor air temperatures, the lower the efficiency of the heat pump system.
This inefficiency can make your heating system burn more energy and drive up your energy bills. Fundamentally, the best way to reduce the inefficiency and avoid high energy bills is to reduce the gap between the outdoor air temperature and your thermostat.
Frequently setting your thermostat at a high temperature, especially in the winter, escalates your house’s energy loss and increases your energy bill.
However, setting your thermostat at a low temperature is not feasible for chilly winter days when you want to keep warm. Luckily, putting your heat pump at the right temperature can help reduce your energy bill and maximize your heat pump’s effectiveness.
To maximize comfort and efficiency, you should set your thermostat to between 68 and 72° Fahrenheit. This temperature is comfortable for most people and will keep everyone warm in typical clothing while minimizing heat loss.
When no one is in your house, setting your heat pump to between 58 and 62 degrees Fahrenheit will enable you to save money on heating without worrying about making a family member cold or uncomfortable.
There are a variety of heat pump thermostats on the market. A programmable thermostat will manage the temperature setting for you. A programmable thermostat is a digital thermostat that can help you pinpoint temperature readings with minimal guesswork.
In recent years, smart thermostats, like a Nest or ecobee, have used advanced AI technology to manage indoor comfort levels. A smart thermostat can even learn based on the environment. These heat pump thermostats are great for maintaining a constant temperature in your home.
Should Heat Pumps Run Continuously in the Winter?
Although heat pumps are less effective in freezing and below-freezing temperatures, a heat pump can technically run continuously in the winter without the assistance of aux heat. However, to save money and energy, you should not run your heat pump continuously in the winter- always turn it off when it is not in use.
For example, if you will be gone overnight or all day, you can turn your heat pump off and set a timer so it turns back on before you return. If you set your timer to turn about half an hour before you get home, it should be warm upon arrival.
Ultimately, turning your heat pump off whenever possible will maximize energy savings. If you are primarily concerned with saving money during wintertime, you can even set your timer so your heat pump turns off for a few hours at night while you sleep, then kicks back on before you wake up!
Will a Heat Pump Work in Defrost Mode
Finally, if you see ice forming on your outdoor unit, then your system is probably in defrost mode. The heat pump might temporarily go into a defrost mode to avoid icing over. If you see ice forming on the outdoor coil, the defrost mode has to melt the ice to prevent system failure.
During the defrosts mode, both the emergency heat strips (or gas backup furnace) and heat pump may be operating at once to maintain an even room temperature. The indoor unit senses the air temperature is too low; emergency heat or furnace will supplement while defrost cycle warms the outdoor coil.
The outdoor coil needs to remain ice-free to prevent damage to the fan motor and compressor inside the outdoor unit.
Overall, the heat pump should be about twenty degrees hotter than the outside temperature when in heat mode. When it is too cold outside for your heat pump to keep up with your heating needs, the Auxiliary heat will supplement it to keep your house warm.
This is often necessary for the winter when heat pumps are less effective, and you should set your heat pump between 68 and 72° Fahrenheit (20 to 22° Celsius) to maximize energy efficiency.
Finally, do not keep your heat pump running continuously in the winter, or your heating bills will be higher- try to turn off your heat pump whenever it is not in use.
- Sustainable Stanford: Energy-Efficient Buildings: Heating and Cooling Equipment
- Washington State University: Electric Heat Lock Out on Heat Pumps
- Aire Serv Heating and Air Conditioning: The Basics of Winter Heat Pump Use