Coming into widespread use in the 1970s in response to a spike in natural gas prices, heat pumps are ideal for Charleston’s mild winters and hot summers. Years ago, heat pumps weren’t practical in climates where winter temperatures fell below the mid-40s. Over the years, advances have made heat pumps an efficient alternative in temperatures down to 0 degrees. Today, thanks to technology and innovation, heat pumps are more efficient than ever.
The seasonal energy efficiency ratio (SEER) measures the cooling efficiency of a heat pump; the heating seasonal performance factor (HSPF) measures its heating efficiency. Both ratings compare the amount of electricity going into the unit to the cooling or heating capacity that comes out. The higher the rating, the greater the efficiency. Federal standards have increased the minimum SEER ratings over the years:
- Before 1980, 6 SEER
- 1980-1985, 7 SEER
- 1986-1991, 8 SEER
- 1992-2005, 10 SEER
- 2006-2014, 13 SEER
In 2015, the minimum standards for heat pump efficiency call for a SEER rating of 14 and HSPF rating of 8.2.
As the SEER number climbs, the amount of power needed to cool your home decreases. For example, a heat pump with a 12 SEER rating uses half of the electricity of a 6 SEER unit. A 10-SEER unit bought in 2005 is about 30 percent less efficient than a newer model with a minimum SEER rating of 14.
The most efficient heat pumps have a SEER rating of 23 and an HSPF rating of 10.2. Heat pumps achieve this efficiency through two significant advances: variable speed motors and 2-stage compressors.
Variable Speed Motors
To achieve maximum comfort, you need the right amount of airflow. Unlike conventional blower motors that have only one speed, variable speed motors operate at different speeds. The key is that a variable speed motor monitors temperature, humidity and other factors and automatically makes adjustments based on the data it receives. For example, a variable speed motor will ramp up its speed in the morning to cool your home to a comfortable level. Once it reaches the desired temperature, it drops down to a lower speed and goes into cruise control mode.
Variable speed fan motors allow for more precise control of airflow throughout your home. Improved airflow offers several benefits:
- Enhanced comfort: A variable speed fan avoids the drastic temperature swings that come with a single-speed motor.
- Increased efficiency: Variable speed blowers use 66 percent less electricity.
- Less noise: A variable speed motor eliminates the whoosh of air when your unit cycles on because the fan motor gradually increases its speed rather than starting from scratch.
- Cleaner air: A variable speed blower continually circulates air throughout your home, allowing filters to catch more dust particles and other indoor pollutants.
Two-stage compressors work similar to motors with variable speeds. A single-stage compressor runs at one level: full blast. Because it cools at only one speed, your heat pump cycles off and on frequently. The constant stopping and starting use excessive energy and wears out your system quicker.
A 2-stage compressor runs on a low setting on milder days and then kicks into high gear to handle Charleston’s hot summer days. The low setting meets your needs 80 percent of the time, which reduces energy consumption. Because your unit runs longer on the low setting, it removes more humidity from your indoor air and leaves you more comfortable. It also prolongs the lifespan of your equipment by eliminating the frequent cycling.
Whether you are interested in the energy efficiency of a heat pump for a custom-built home, want to add heating and cooling to a historic home or need to upgrade your current HVAC system, our comfort specialists at AC Heating and Air Conditioning have the experience and expertise you need. Check out the energy-efficient heat pumps we offer at AC Heating and Air Conditioning or call us at (843) 277-9928.