HOMEOWNER RESOURCES
What to consider when choosing a heat pump
The primary factors to consider when choosing a heat pump include performance, efficiency, and sizing.
Performance
Depending on how well a heat pump modulates to match your home’s heating and cooling needs, it can be classified as 1) single-speed (good), 2) two-speed (better), or 3) variable-speed (best).
Single speed: This means the heat pump runs full ON or is OFF. With these models, your system turns ON at 100% capacity and then OFF until your thermostat or control system reaches the temperature setting you have selected. While the least expensive initially, these systems tend to result in temperature swings and also are the least efficient.
Two speed: These systems allow for two levels of modulation — a low capacity one to handle a smaller demand and a larger one to meet heavier demands. If conditions exist that 100% capacity is not required, the system can operate at a lower speed, offering partial capacity to reach your desired indoor temperature.
Variable speed: Variable speed (often referred to as inverter) technology allows the system to run at a speed that maximizes both comfort and energy-efficient operation. A variable speed system is designed and engineered specifically to provide the output needed at the lowest consumption of power.
In addition to temperature control, the benefits of modulating equipment include:
1) Better indoor air quality by circulating more air through your air filters and around your home;
2) More effective dehumidification increases building longevity and prevent mold, mites, and pests in your home; and
3) Quieter operation by adjusting airflow to be more consistent and meet the exact demands of your home.
Efficiency
Heat pumps are rated on two efficiency metrics, SEER (Seasonal Energy Efficiency Rating) for cooling and HSPF (Heating Seasonal Performance Factor) for heating.
The higher the SEER and HSPF, the higher the efficiency of the system.
SEER: The Department of Energy has established 14 SEER as the minimum allowable cooling efficiency for residential, air-source, split-system heat pumps. Generally speaking, models rated at 18 SEER and above should be considered highly efficient heat pumps. Some of the highest efficiency air-source heat pumps are rated at up to 20.5 SEER.
HSPF: The Department of Energy has established 8.2 HSPF as the minimum efficiency for residential, air-source, split-system heat pumps. While some of the highest-performing air-source heat pumps are rated at 13 HSPF, anything about 10 HSPF should be considered to be a high-efficiency model.
If you live in a cold winter area with mild summers, HSPF, will be the more important rating to consider for a heat pump. Conversely, if you live in a hot climate with mild winters, SEER will be more important.
Sizing
Basics: The size of your heat pump isn’t about the actual size of the machine; it’s about the maximum amount of heating and cooling capability it has.
HVAC sizes are discussed in both BTUs (British Thermal Units) and tons. A BTU is the amount of energy needed to increase the temperature of one pound of water by one degree Fahrenheit: typically the amount of energy in one match. Heat pumps and air conditioners are typically rated in tons, where one ton = 12,000 BTU. This is how much heat one ton of ice absorbs to completely melt this same ton of ice. This somewhat archaic “tonnage” is a carryover from the old days of keeping things cold with blocks of ice.
In order to maximize performance, efficiency, and comfort it is critical to choose the right-sized heat pump for your home. Too small a unit, and you may not be able to fully cool or heat your home. Too large a unit , and you’ll waste money installing and operating excess heat and cooling capacity. The oversized unit will also turn on and off frequently, which wastes energy.
Load calculations: How much it takes to heat and cool your home at the typical extreme temperatures of your climate is called the heating and cooling load. The process of figuring out how much it takes to do this is called a load calculation.
To calculate heat pump size, HVAC industry follows a standard sizing method known as Manual J, established by the Air Conditioning Contractors of America, a trade organization.
The main factors considered in Manual J are:
1. The local climate and how many days a year you need active heating and cooling
2. The home’s layout, such as square footage and shape
3. The number and location of windows
4. How much air infiltration occurs
5. How much insulation the home has
6. How many people live in the home and appliances that generate heat
In addition to the somewhat involved process that includes several assumptions, a drawback of Manual J are the fudge factors that tend to result in oversized equipment.
As an alternative method, using data from energy bills and correlating them with measured temperatures provides a home’s actual heating and cooling loads, which can be referenced when sizing a heat pump.
HOMEOWNER RESOURCES
Top heating and cooling tips for homeowners
What is a heat pump and why should I upgrade?
A heat pump provides all-in-one heating and cooling for perfect year-round comfort. Not only that, it operates more than 3x efficiently compared with a standard furnace.
What is the difference between heat pumps and furnaces?
Heat pumps and furnaces heat your home – but in different ways. The most significant difference between furnaces and heat pumps is that furnaces create their own heat.