An inverter heat pump is a heat pump that operates at variable speeds to provide precise heating and cooling temperature control. They use what’s known as an inverter drive or inverter compressor to operate at variable speeds. Trane ducted system variable speed heat pumps and ductless heat pumps utilize inverter technology.
By Anne Fonda
Commonly known as variable-speed heat pumps, these heating and air conditioning units use a variable-speed compressor that automatically shifts speeds during the day. Depending on the temperature inside your home and your thermostat settings, the compressor will decrease or increase its speed as it transfers heat energy.
When the demand for heating or cooling is low, the inverter reduces the system’s output, which limits the total amount of energy used. By running at a low speed and maintaining the indoor temperature, a variable-speed heat pump reduces the number of start cycles that occur.
Inverter heat pumps generally operate at 30%-100% capacity depending on the difference between your home’s ambient temperature and what temperature you have set the thermostat at.
As we mentioned, an inverter heat pump operates at a variable speed. This sets it apart from a single-stage or two-stage heat pump.
A single-stage heat pump is either off or on. It runs full power to heat or cool your home and shuts off when the desired temperature is reached. Since HVAC units use the most power when they turn on, this frequent turning off and on can use a lot of energy.
A two-stage heat pump operates at low and high speeds. It offers more consistent temperature control than a single-stage unit and better humidity control. It’s also more energy efficient.
An inverter/variable-speed heat pump has a heat pump inverter that enables it to quickly change the amount of power it uses and the amount of refrigerant it transfers to and from the indoor unit(s). With the INVERTER, the outdoor unit only uses the precise amount of power needed to reach the preferred temperature.
So, a 4-ton inverter heat pump will offer more precise temperature and humidity control than a similarly-sized single-stage or two-stage unit. By going with variable speed technology, you can increase your home comfort, save energy, and save money on your energy bills.
A heating and cooling system is only as good as its installation. Possibly the most important thing in the process is working with HVAC professionals who will go to the effort of precise HVAC system sizing.
Don’t assume that your current heat pump or AC unit is correctly sized for your home. A lot of HVAC systems are either oversized or undersized. In addition, a unit that was correctly sized and installed may now be oversized if you have upgraded your home’s insulation, windows, and doors. For example, instead of the traditional 600 sq. ft./ton for residential, it might be closer to 1,000 sq. ft. per ton.
What size unit do you need? The following table can give you an idea, based on the size of your home. But again, work with an HVAC professional for precise sizing.
| Home size (sq. ft.) | Unit Size (tons) | Unit Size (BTUs) |
| 1,200 sq. ft. | 2-ton heat pump/2-ton mini split | 24,000 BTUs |
| 1,800 sq. ft. | 3-ton heat pump/3-ton mini split | 36,000 BTUs |
| 2,400 sq. ft. | 4-ton heat pump/4-ton mini split | 48,000 BTUs |
| 3,000 sq. ft. | 5-ton heat pump/5-ton mini split | 60,000 BTUs |
Notice that one ton = 12,000 BTUs. For precise sizing, work with an experienced HVAC company. Ask them about doing a Manual J calculation and ductwork sizing for a ducted heat pump and other calculations for a zoned ductless HVAC system.
The best variable speed/inverter heat pump is one that is sized correctly for your home and has the highest SEER2 and HSPF2 energy efficiency ratings. A traditional system will include an outdoor heat pump and an indoor air handler while a ductless system will include an outdoor mini-split heat pump connected to one or more interior units.
Considering upgrading to an inverter heat pump system? Contact your local Trane HVAC experts to find the ducted or ductless system that’s right for your home and your budget.
Anne Fonda, Content Writer at Trane Technologies
A Content Writer with Trane Technologies, Anne Fonda researches topics and writes for Trane® and associated residential HVAC brands. She works in collaboration with Trane Technologies subject matter experts, offering easy-to-understand, informative content on complex topics. Her goal is to help consumers make informed decisions on the products and services they need.
She has written for HVAC and other service provider websites for over 16 years. Before transitioning to web content writing, Anne had a 14-year stint as an award-winning journalist. She graduated cum laude from the University of Missouri-Columbia School of Journalism. When she’s not working, Anne enjoys playing word games, reading, gardening, spending time with family, and visiting gardens and museums.
Expert review by: Kimberly Sexton, Senior Systems Engineer
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