Energy efficiency ratings measure how well your HVAC system converts energy into heat or cool air. Use an HVAC efficiency rating when you are shopping for a new system, to help you choose the unit that will save the most energy and be less expensive to run. There are a variety of heat and A/C efficiency ratings, but the most common types are HSPF, SEER and AFUE. Here are the explanations of what each one means.
BTUs and energy efficiency ratings
British Thermal Units (BTUs) are how heat energy is generally measured. A BTU is the amount of energy it takes for you to raise the temperature of a pound of water by a single degree Fahrenheit. When evaluating the energy efficiency rating options below, calculate how much heating or cooling a given unit provides per BTU.
Heating Seasonal Performance Factor (HSPF)
This heating rating measures the BTUs of heat that a system puts out over the course of a heating season, divided by the total electricity used in watt-hours. So, if you have a unit that pumps out 60,000 BTUs of heat in a season and uses 6,000 watt-hours to do it, you have an HSPF of 10. The new minimum unit efficiency for heat pumps after 2023 is 8.8. The higher the HSPF number on any unit, the more energy efficient it is.
Seasonal Energy Efficiency Ratio (SEER)
This commonly used A/C efficiency rating is the cooling counterpart to HSPF, measuring the BTUs of cooling your unit produces over a season, divided by the energy used. If your 24,000 BTU air conditioner uses 1,500 watt-hours, it has a SEER of 16. The 2023 standards now require all units to have a SEER of at least 14. Again, the higher the SEER number on a unit, the more energy efficient it is.
Annual Fuel Utilization Efficiency (AFUE)
The Department of Energy requires this thermal efficiency rating to be displayed on all new furnaces sold in the U.S. The AFUE rating measures how well your furnace turns fuel energy into heat for your home.
You may have a gas furnace that burns 10,000 BTUs of energy and puts out 9,500 BTUs of heat for your home. Dividing the BTUs of heat by the BTUs of fuel and then multiplying that number by 100 gives you a percentage. In this case, your AFUE is 95%. High-efficiency units have an AFUE of 90%–98.5%.
Factors that influence HVAC efficiency ratings
When evaluating any heat or A/C efficiency rating, it helps to understand what factors influence performance. Keeping these things in mind will help you get the maximum efficiency from your system.
System age
Very old systems were not always built to be energy efficient. As components age, they don’t run as smoothly, consuming more energy. Modern engineering has made tremendous progress in improving capabilities to save energy while improving performance.
System size
A correctly sized system that matches the square footage of your home will be the most energy efficient. If you buy a system that is too small, it will have to work overtime to keep your home comfortable, using more energy. An oversized system will blast your home with warm or cool air, prompting it to shut down. When the temperature inside rises or falls, your thermostat will kick it on again. The result is short cycling that wears out the components and uses more energy than necessary.
Installation quality
An experienced HVAC professional will place your equipment in the right location. An A/C system should be out of the sun and have plenty of air circulation. Understanding manufacturer specifications is important.
Ductwork condition
You want to make sure your ducts are not leaking air. They also should be clean, so that air moves through them efficiently. You can further improve the efficiency of your system by insulating your ductwork.
Thermostat setting
Making sure your thermostat supports an efficient HVAC system is a matter of quality, location and its settings. You want a thermostat with an accurate sensor, ideally one that you can program and that has features which save energy, like monitoring your system and giving you control by location in your home. It should be centrally located for the most accurate readings. Be sure to set it within a reasonable temperature range. Keeping your home very warm in the winter and exceptionally cool in summer uses more energy.
Insulation levels
A well-insulated home keeps the cool air inside during summer and warm air inside during the winter. In addition to insulation in attics, walls, ceilings and floors, be sure to add weather stripping around doors and windows and seal all cracks.
Air filter cleanliness
A clogged air filter makes your system work harder. New filters are inexpensive and easy to switch out. Changing them every three months is a good idea. Then your high-efficiency rated HVAC will enjoy peak performance.
Climate conditions
The HVAC efficiency rating of your system varies by climate. In northern regions, you need a higher heating rating. In the south, you want a higher cooling efficiency rating.
Maintenance
Invest in performing regular maintenance on your unit. It is good advice to have your system checked every fall and spring to make sure it is ready for a cold winter and a hot summer. The energy rating system helps you buy an efficient HVAC unit, but maintenance keeps it running efficiently after installation.
Static air pressure
When there is resistance to air flowing through your system, usually caused by a clogged filter, dirty air ducts or blocked vents, your system works harder to push out air. That lowers its efficiency, no matter what its HVAC efficiency rating is.
What is a good A/C efficiency rating?
Your A/C unit efficiency rating is the key to understanding how well your system uses power to make your home comfortable. It is extremely helpful when you are evaluating your options and deciding what unit to buy. It can also help you decide when it is worth it to replace your system. No A/C system lasts forever. Knowing the efficiency of your current system and keeping an eye on the energy efficiency rating of a new system will help you decide if you save enough power to justify the upgrade cost.
A good energy efficiency number ultimately depends on how much better it is than your current system and how it compares to current Department of Energy standards.
How are HVAC energy efficiency ratings calculated?
Accurately measuring HVAC efficiency depends on understanding how each HVAC efficiency rating is calculated. Here is a summary:
- HSPF = Total BTUs of heat output over a season ÷ Total electricity used, in watt-hours
- SEER = Total BTUs of cooling output over a season ÷ Total electricity used, in watt-hours
- AFUE = (BTUs of heat output ÷ BTUs of fuel input) × 100
Common misconceptions about energy efficiency ratings
An energy efficiency rating only tells you what is possible. What matters is how your system works in real life. That is where a few misconceptions can interfere with you getting the most from your system.
Myth #1: High SEER ratings guarantee energy savings
A high HVAC efficiency rating does not guarantee anything. If your unit isn’t properly installed and maintained, and you do nothing else in your home and habits, you may not achieve the savings that a high rating suggests is possible.
Myth #2: The higher the efficiency, the more maintenance required
Some people worry that a high-performance system with a high energy efficiency rating costs a lot to maintain. In many cases, well-designed, efficient systems are easier to keep running well. The key is to have a professional you trust take care of the system with regular service and you will find maintenance to be largely routine.
Myth #3: Upgrading a single component can improve efficiency overall
Your HVAC system is just that — a system comprised of many parts. How they work together is what determines the real energy efficiency you can achieve. If you have drafty windows and little insulation, or your ductwork is leaky and dirty, a unit with a great energy efficiency rating may turn out to be costly to run as it struggles to maintain a comfortable temperature in your home.
Myth #4: Bigger is better
While you don’t want an undersized A/C system, one that has too much capacity, even with a high A/C efficiency rating, will blast out cold, shut off, then have to turn on again to blast out cold again in a series of inefficient short cycles.
Myth #5: The less the system runs, the less energy it uses
In extreme temperatures, when your unit is running full-out and non-stop, it is using more energy. Modern variable speed units, however, run at a very low capacity for longer periods, which may use less energy than one that is constantly turning on and off in cycles of 100% capacity each time.
Constellation Home can help
Regular maintenance is convenient, easy and wallet-friendly with Constellation Home Protection. We take care of your HVAC needs, providing advice, handling installation and taking care of the details of maintenance, repair and getting parts. Service plan options vary by state, but often include heating and air conditioning, your water heater, plumbing and electrical systems and major appliances.
Constellation Home has been serving customers for over 30 years and offers a 100% satisfaction guarantee. With easy priority scheduling and 24/7 service from local, licensed professionals, you have reliable expertise that helps you optimize your home’s energy efficiency. Find out what is available in your area and request an estimate.
