Energy efficiency is an important factor when choosing any new HVAC unit. If you’re considering a new heat pump for your home, it is important that you look at how energy efficient it is when cooling and also its heating efficiency. The heating efficiency of a heat pump is measured in HSPF. This guide will explain exactly what HSPF means and how much you can potentially save if you choose a unit with a higher HSPF rating.
How Heating Efficiency Is Determined
Calculating the energy efficiency of a heat pump is much more difficult than determining how energy efficient a furnace is. As long as a furnace is properly maintained and functioning effectively, its energy efficiency won’t ever change. This isn’t the case with heat pumps since they sit outside. This means that the amount of energy they use in a given time can fluctuate based on the outdoor air temperature. The amount of electricity a heat pump consumes if it runs for a full hour doesn’t change. But the total number of hours the unit runs in a day depends on how warm or cold it is outside.
The energy efficiency of a furnace is measured in AFUE or annual fuel utilization efficiency. This expresses what percentage of heat energy it produces compared to how much energy it consumes. The AFUE for gas furnaces ranges anywhere from 80% to 98.5%, which means that some of the energy they use is wasted.
Another way to look at the energy efficiency of any heating unit is through a metric known as coefficient of performance (COP). This expresses how many units of heat energy are produced for every unit of electricity consumed. A furnace that was 80% efficient would have a COP of 0.8.
Modern heat pumps are often 300% to 400% efficient. This would equal a COP of 3 or 4. This means that the unit would put out three to four times more heat energy compared to the amount of electrical energy they use. The problem with looking at efficiency in this way is that the amount of heat energy a heat pump produces at a time decreases the lower the outdoor temperature is. This means that the COP of a heat pump doesn’t remain constant throughout the entire heating season as it does for a furnace.
Heat pumps work by transferring heat from the air outside to the air inside a building. The reason that the heat production decreases in colder temperatures is simple. The colder the air gets, the less heat energy it contains.
The COP of a heat pump fluctuates based on the outdoor temperature. This is why you can’t just look at heat production and energy usage over one hour or day. The only accurate way to gauge a heat pump’s energy efficiency is to look at how much heat it produces over the entire year or heating season. This is compared to how much electricity it uses in the same period, which is where HSPF ratings come in.
Understanding HSPF Ratings
HSPF stands for heating seasonal performance factor. It is used to approximate how much total energy a heat pump would use over the course of a single heating season, i.e. from late fall to early spring. HSPF is just a ratio of the total kilowatts of electricity a heat pump uses to the BTUs of heat it produces in one heating season. The higher a heat pump’s HSPF rating is, the more energy efficient the unit is and the less it will cost to run it.
To calculate a heat pump’s HSPF rating, the unit must first be tested to determine how much heat it produces in different conditions. This test is designed to simulate a typical heating season and find out how efficiently the heat pump works in warmer and colder temperatures.
As of January 2023, all new heat pumps must have an HSPF rating of at least 8.8. If you opted for a more efficient 12 HSPF heat pump, it would use approximately 25% less energy than an 8.8 HSPF unit. Some central heat pumps can be as high as 13.5 HSPF, but any model that is 10 HSPF or higher is considered a high-efficiency unit.
HSPF vs. HSPF2
The U.S. Department of Energy also switched to the new HSPF2 rating scale at the start of 2023. There’s no need for you to fully understand the difference between the two ratings. This is since they still measure the same thing and show the total energy usage compared to heat production over one season.
The only difference between the two is that HSPF2 has slightly different testing parameters so that the tests more accurately simulate real-world conditions. Specifically, HSPF2 tests the units at a higher static pressure, which refers to how much airflow resistance there is in the duct system. The higher the static pressure is, the harder the blower has to work to circulate air through the system. This results in the heating effectiveness decreasing while the energy usage increases.
HSPF2 ratings are 15% lower than HSPF ratings. This means that a unit that is rated at 10 HSPF would have an HSPF2 rating of 8.5. A unit that meets the minimum of 8.8 HSPF has a rating of 7.5 HSPF2.
SEER or HSPF: Which Is More Important?
When deciding which heat pump is best for your home, you also need to focus on SEER ratings. SEER stands for seasonal energy efficiency ratio. It measures the same thing as HSPF except that it is a ratio of energy usage to BTUs of cooling instead of heating.
In climates with milder summers and much colder winters, it’s much more important to choose a unit with a higher HSPF rating. The annual heating costs will be much greater than the annual cooling costs. In places like Texas, where the winters are fairly warm and the summers are much hotter and more humid, SEER ratings are far more important. A heat pump will run on cooling mode most of the year and only rarely be used for heating.
In our area, opting for a 12 HSPF heat pump instead of the minimum 8.8 HSPF would typically only save you somewhere between $50 and $150 a year in heating costs. This means it may not be not worth the extra cost for a much higher HSPF unit. On the other hand, it can definitely be worth it to pay more for a heat pump with a higher SEER rating. This can save you more money each year in cooling costs.
The minimum for new heat pumps in Texas is 15 SEER (14.3 SEER2). If you chose an 18 SEER (17.2 SEER2) unit, your annual cooling costs would be around 21% lower than with a 15 SEER unit. A high-efficiency 20 SEER (19.1 SEER2) unit would use around 35%-40% less energy than a 15 SEER unit. In this case, you could potentially save a few hundred dollars a year or a few thousand over the life of your heat pump depending on the size of the unit.
Call the Professionals
On Time Experts is a top-rated HVAC contractor. We offer professional heat pump installation services for customers in Garland and throughout the Dallas-Fort Worth area. If you’re looking to install a new heat pump or replace your existing unit, our technicians can help you determine which model will work best in your home. We also install central ACs, furnaces and mini-splits, and our team can help with your heating and cooling repair and maintenance needs as well. For more information on the range of heat pumps we carry or if you need to schedule any HVAC or plumbing service, give us a call today.