Due to their high energy efficiency, heat pumps are becoming an increasingly popular option for homeowners. While heat pumps can be effective in all climates throughout the summertime, it’s important to understand their limitations in the wintertime and how humidity may affect their efficiency. This article will discuss how these systems function in various climates, including drier ones.
A Note on Heat Pump Types
Heat pumps come in two main categories: air source and ground source. Air source heat pumps are the most common type found in households because of their affordability and ease of installation. These systems operate by extracting heat from the outside air and transferring it indoors during the winter months. In the summer, they reverse the process, functioning similarly to an air conditioner by moving heat from inside your home to the outside. This makes them a versatile option for both heating and cooling.
Ground source heat pumps, on the other hand, draw heat from the ground or a nearby water source. While these systems are significantly more expensive and invasive to install due to the need for underground pipes, they offer higher efficiency, especially in extreme temperatures. Geothermal heat pumps are effective in a wide range of climates, as the ground maintains a relatively stable temperature throughout the year, leading to consistent performance.
How Does an Air Source Heat Pump Work in Winter?
An air source heat pump operates by transferring heat from one location to another using refrigerant. The process begins at the outdoor condenser unit, where a blower fan pulls in outside air and passes it over the condenser coil. The refrigerant inside this coil is cold and at a low pressure. Since heat naturally moves from warmer to cooler areas, thermal energy from the outdoor air transfers into the refrigerant, causing it to absorb heat and turn into a gas.
This now warm, gaseous refrigerant is then pumped indoors to the air handler unit. Inside this unit, a blower fan draws in cool air from your home and circulates it over the evaporator coil, which contains the hot, high-pressure refrigerant. As the indoor air passes over the coil, the refrigerant releases its heat into the air, warming it up. The heated air is then blown through your ductwork, distributing warmth throughout your home. Meanwhile, the refrigerant cools down, condensing back into a liquid state.
The refrigerant, now in liquid form, flows back to the outdoor unit through an expansion valve. This valve reduces the pressure of the refrigerant, cooling it further so that it can absorb heat from the outdoor air again. This cycle of compressing, heating, expanding, and cooling continues until your home reaches the set temperature on your thermostat.
How Does Temperature Affect System Performance?
When it comes to air source heat pumps specifically, temperature plays a role in overall operating efficiency. You always get maximum operating efficiency at temperatures above freezing. However, when outdoor temperatures dip below freezing, a heat pump will become less efficient. It can still produce heat for your home, except it’s going to take a lot more energy to do so.
Eventually, when outdoor temperatures get too low, heat pumps will rely on their auxiliary heating function to warm your home. This mode works similarly to an electric baseboard heating with an internal electric heating element. The indoor air handler unit will circulate air from your home over the heating element so it can be warmed up and redistributed to the various rooms throughout your home. It’s crucial to know that a heat pump that uses auxiliary heating is going to require much more electricity to function effectively.
How Does Humidity Affect System Performance?
The impact of humidity on heat pump performance depends primarily on whether the unit is operating in heating or cooling mode. When running in cooling mode, heat pumps reduce indoor humidity as a side effect of cooling the air. This occurs because, like traditional air conditioners, heat pumps have an evaporator coil that cools the air as it passes over it. If the air is humid, moisture will condense on the coil, drip into the drain pan, and be carried outside by the condensate line. This process reduces indoor humidity levels. However, in very humid conditions, your heat pump may need to run longer to both cool the air and reduce moisture levels, which can increase energy consumption.
On the other hand, heat pumps make indoor air drier in winter, as heating generally lowers relative humidity levels. The issue is that low humidity causes moisture to evaporate more quickly from your skin. This creates a cooling effect that may lead you or other household members to adjust the thermostat to a higher setting for comfort, resulting in higher heating costs. Dry climates do not directly impact heat pump efficiency.
If you’re concerned about balancing air moisture levels in your home, whole-home humidity control can be a great addition. A HVAC professional can integrate one into a heat pump system. It will introduce moisture into the air when your heat pump runs, helping to maintain an ideal indoor humidity level between 30% and 50%. This improves comfort and reduces the need to frequently adjust your thermostat, optimizing the overall efficiency of your heating system.
Using a Dual-Heating System
In climates where temperatures dip below freezing frequently, relying solely on a heat pump is not going to be a very energy-efficient way to heat your home. However, many homeowners find investing in a dual-heating system solves this problem. This typically entails having a heat pump that functions both as a cooling system and a heating system when temperatures are above the freezing point.
When temperatures dip below freezing, and the heat pump’s efficiency is compromised, the secondary heating system kicks in. This is usually a furnace that runs on a cost-effective fuel like natural gas or propane. This type of dual-heating system gives homeowners the ability to have an energy-efficient heating system, regardless of the outside temperature.
Ducted vs. Ductless Systems
Heat pumps come in two main configurations: ducted and ductless. Homeowners with existing ductwork often choose a ducted heat pump system since it integrates seamlessly with their current setup.
On the other hand, a ductless mini-split heat pump can be a more cost-effective solution for homes without a forced air system because of the costs associated with installing ductwork. In addition, a mini-split system offers enhanced energy efficiency in several ways. It eliminates heat loss that can occur through leaks and gaps in ductwork. It also provides greater control over the temperature in individual rooms, enabling homeowners to adjust settings as needed, optimizing energy use and reducing overall heating and cooling bills.
Contact the Pros
At Bumble Breeze, we have served the residents of Las Vegas, NV and the surrounding areas since 2018. We install, maintain, and repair heating and cooling systems, including heat pumps. In addition, we can help with all your indoor air quality and plumbing needs. Contact us today to schedule an appointment with one of our experienced team members.
