A heat pump with this feature will turn on the supplemental
A heat pump is fully capable of heating in a cold climate without supplemental heat however it would be quite oversized on the cooling capacity so allowances must be made. Often a system is sized to achieve a balance point around 30F which calls for supplemental heat below that.
Your auxiliary heat, or secondary heat source, should come on when your heat pump is struggling to heat your home effectively. The thermostat will trigger auxiliary heat when: The outside temperature is below 40 degrees or a set aux heat trigger temperature. The heat pump is in defrost mode.
Supplementary Heat Sources
Since air-source heat pumps have a minimum outdoor operating temperature (between -15°C to -25°C) and reduced heating capacity at very cold temperatures, it is important to consider a supplemental heating source for air-source heat pump operations.
Cost of Energy Bills in AUX Heat Mode
Because your heat pump and backup heat source work together, AUX mode consumes more energy. This leads to increased energy bills — your costs may be up to 50% higher when the device is using AUX heat.
Auxiliary heat strips supplement the heat pump and produce warm air to quickly heat your home. Those heat strips use substantially more energy and will increase your electric bill.
More often than not, the aux heat is coming on because the temperature in the home is set too high. You are asking your HVAC system to work too hard to maintain a comfortable temperature. Setting the thermostat for somewhere between 62-68 degrees is all you should need to do to get the problem under control.
But heat pumps work to cool homes, too, and are capable of working in hot weather, just like an air conditioner. According to the Department of Energy, heat pumps work as well at conditioning an equivalent-sized space as an air conditioner but they dehumidify better and work more efficiently.
Supplement Heat to Maintain Comfort
Auxiliary heat is an integral component of air-source heating systems in cold weather, using electricity to supplement heat pumps in extreme temperatures.
A range of 68-70 is the best setting in winter if you want to save money because your furnace or heat pump doesn't have to work as hard as it does to reach a higher set temperature. The DOE says the smaller the difference is between the indoor and outdoor temperatures, the more you can save.
This can cause concern, as auxiliary heat typically is not supposed to run all the time. While it's normal for auxiliary heat to kick in during exceedingly cold temperatures, running it too long may indicate an issue with the heat pump.
Heat pumps do not operate as efficiently when temperatures drop to between 25 and 40 degrees Fahrenheit for most systems. A heat pump works best when the temperature is above 40. Once outdoor temperatures drop to 40 degrees, heat pumps start losing efficiency, and they consume more energy to do their jobs.
Some heat pumps are designed operate independently without back up heating, while others are designed to use a back up heating system. Whether or not you need a backup heat source for your heat pump will depend on the type of heat pump you purchase, your climate zone, and the design and efficiency of your home.
Supplemental Heating – Equipment that provides the additional heating capacity to the primary heating equipment when needed (e.g., electric baseboard heaters, wood stoves, space heaters, a mini-split heat pump, electric resistance elements in a heat pump, a furnace in a dual fuel heat pump system).
Most cold-climate heat pumps can run at total capacity until the outdoor temperature gets to about 5 F or below. It will still heat your home at those lower temperatures, but not necessarily keep it as warm as you may typically like. That's where backup heat sources come in.
Homes need to be well insulated for heat pumps to be effective because the devices work at lower temperatures and so will struggle to get the house warm and keep it to temperature. They work better with lower-temperature heating systems, such as underfloor heating.
Heat pump airflow can be increased by cleaning your heating and cooling system's evaporator coil, which is usually taken care of during routine maintenance visits from your contractor. Your technician may also adjust the heat pump's fan speed during preventive maintenance to improve air circulation.
Optimal Heat Pump Settings for Summer
During the summer months, the ideal setting for your heat pump is around 78 degrees Fahrenheit (25.5 degrees Celsius) according to the US Department of Energy. This setting allows the heat pump to efficiently cool your home while reducing humidity and energy consumption.
Simply put, it means you should never set your thermostat for a temperature more than 20 degrees cooler than the outside air. Why not? Most air conditioning systems can only handle a 20-degree difference between the outside and inside air temperatures.
During heat waves, experts, including utility companies, recommend keeping your thermostat no more than 20 degrees cooler than the outdoor temperature. For instance, if it's 100 degrees outside, aim to set your thermostat to at least 80 degrees.
One of the most common reasons for a heat pump constantly running stems from a thermostat set too low or too high. A thermostat set too low during the peak of summer will cause your heat pump to run extended cycles. A good way to avoid this is to ensure you stay realistic with your thermostat settings.
Auixiliary Heat will turn on automatically when heat can no longer efficiently transfer heat from the outside air to heat pump. This is when the outside is around 35-40 degrees and the indoor temperature is around three degrees cooler than the thermostat setting.
It's Defrosting
To protect the outdoor coils from freezing up in the winter, heat pumps go through a defrosting period every hour or so in which they are truly blowing out cold air. This defrosting period only lasts a few minutes and should not affect the overall temperature of your home.
Key takeaways. Heat pumps typically last around 10 to 15 years, but some experts claim a well-maintained heat pump can last closer as long as 20 to 25 years.