Energy Ratings: More Than Alphabet Soup, They Guide You to Savings
A basic understanding of energy ratings for air conditioning and heating systems will go a long way toward helping you decide which equipment is right for your home. Energy Star is a program of the U.S. Environmental Protection Agency (EPA) which promotes voluntary reductions in energy use by providing consumers with useful information about energy efficiency. The program then awards approval ratings to qualifying equipment. Cooling and heating equipment is tested by the manufacturers to determine how they perform against specific industry standards.
A number of acronyms are used for energy ratings for various types of cooling and heating systems. They're useful in comparing the energy efficiencies of air conditioning and heating systems provided by different manufacturers or within an individual manufacturer's product line. Here's a breakdown of the most common energy ratings.
- SEER, or seasonal energy efficiency ratio - This is a measure of the total cooling output (expressed in Britisth thermal units (BTUs)) and divided by the total electrical energy input (expressed in watt-hours) of an air conditioning system over a complete cooling season. The higher the SEER, the higher the energy efficiency of the system and the lower the operating costs. SEER ranges from 6 for systems built in the 1970s to 16 and higher for systems built in the past few years. To receive the Energy Star label, central air conditioning systems must have a SEER of at least 14 and air-source heat pumps must have a SEER of 14.5 or higher.
- EER, or energy efficiency ratio - Unlike SEER, which is based on a complete season, the EER is an instantaneous measure of a cooling system's energy efficiency, tested at standard conditions in the manufacturer's laboratory. EER is expressed in BTUs per watt-hour. Energy Star-qualifying central air conditioners and air-source heat pumps must have minimum EER energy ratings of 12.
- COP, or coefficient of performance - This is an energy efficiency ratio that can be applied to both cooling and heating systems. COP is calculated using the same energy units for input and output, so it's a dimensionless ratio.
- HSPF, or heating seasonal performance factor - HSPF is the ratio of energy output to energy input over an entire heating season for a heat pump. HSPF is expressed in BTUs per watt-hour. As with SEER, the higher the HSPF, the more efficient the heat pump. Energy Star-qualified heat pumps must have minimum HSPF energy ratings of 8.2 for split systems and 8.0 for packaged units.
- AFUE, or annual fuel utilization efficiency - This is a measure of heating furnace efficiency. It's the ratio of the value of the heat actually delivered to the home from a furnace to the value of the fuel burned in the furnace to generate that heat. Thus, an AFUE of 80 tells you that 20 percent of the value of your heating fuel is lost rather than used to provide heat to your home. The Department of Energy (DOE) requires that new heating furnaces have an AFUE of at least 78, although equipment with AFUEs in the 90s is available.
The SEER, EER, COP and HSPF energy ratings are all determined by manufacturers using the standards set forth in the Air Conditioning, Heating and Refrigeration Institute Standard 210/240. For air conditioners and heat pumps, the SEER and HSPF ratings are the most useful for determining the actual expected efficiency of any given system, since they're determined over an average cooling or heating season rather than as an instantaneous measure of performance at standardized operating conditions.
Considerations Before Buying a New HVAC System
You can save significant amounts of money on your cooling and heating bills by investing in highly efficient air conditioning and heating systems. But there are potential trade-offs you should consider as you're selecting the equipment for your home. Unfortunately, the most energy efficient equipment usually costs more to buy and install than less sophisticated systems, so you need to factor the extra upfront cost into your economic calculations as you determine the value to you of various choices.
You want to install the smallest air conditioning system in your home as possible in order to reduce your upfront equipment costs, but you don't want the system to be too small to effectively cool your home. An undersized system will work too hard trying to maintain your thermostat settings and its continuous running could over-dry your indoor air. If your system is oversized, it will cycle off and on too frequently to maintain an even temperature throughout your home and it won't reduce humidity levels effectively.
Reduced Wasted Energy Before You Buy
Before you select the efficiency level that best fits your needs for your new air conditioning system, there are some things you can do that might reduce the size of the equipment that you'll need. By improving your home's overall tightness, you can cool and heat your living space with a smaller system than you might currently need, thus reducing the size of your investment in new equipment. Here are some ways you might be able to improve your home's energy efficiency with investments that might give an even better return than your investment in the additional cost of higher efficiency air conditioning equipment:
- Check your insulation levels and upgrade it wherever feasible, especially in your attic where additional insulation can be economically installed.
- Have your HVAC contractor inspect your ductwork and seal any leaky seams or connections between sections. Ducts that run through unconditioned spaces such as your attic should be well-insulated to prevent energy losses.
- Improve air circulation with ceiling fans to maintain room comfort at higher thermostat settings.
- Provide shade for your outdoor air conditioning unit. Deciduous trees or shrubs that shade the unit on hot summer days will improve the efficiency of the equipment. Be sure grass and shrubs are trimmed well away from the unit to allow unobstructed airflow.
- Consider applying heat-reflecting paint or other coatings to your exterior walls and roof. Reflecting a significant portion of the sun's radiant heat will reduce your air conditioning load.
- Use draperies or other window coverings to keep heat and sunlight out in summer and to allow sunlight in on sunny winter days.
- Plan to have a regular maintenance contract with your HVAC contractor to keep your system running efficiently and to avoid preventable air conditioning problems.
Once you've tightened up your home and reduced your cooling demand as much as possible, you can work with your HVAC contractor to select new air conditioning and heating equipment that's properly sized for your system and that meets or exceeds the minimum energy. A well-designed HVAC system operating in an energy-efficient home will give you many years of home comfort with low monthly fuel bills. Every situation is different, so you should familiarize yourself with energy efficiency concepts and terminology and enlist the aid of your HVAC contractor in choosing the best ways to reduce your energy costs while keeping your home comfortable.
If you have questions regarding energy ratings and choosing the right HVAC equipment for your home, contact the experts at Comfort24-7. We proudly work with homeowners and businesses throughout Chicago, northwest Indiana and southwest Michigan.