What are the efficiency ratings for HVAC systems?
When purchasing an HVAC system for replacement (retrofit), or a new home, you will hear abbreviated terms like SEER, BTU, AFUE, CFM and so many more.
These terms are ratios and measurements of energy efficiency and operating outputs in heating and air conditioning systems. Some terms like BTU, kilowatt, tonnage, and CFM are for measuring size and operational outputs. In this article, we are going to explain the terms that measure energy efficiency. Each term is a ratio or rating for a particular type of HVAC unit. These would be SEER, HSPF, COP, AFUE, EER, and CAE. The definitions for each are listed below (HVAC Efficiency Terms). As a buyer or researcher thinking about purchasing a high-efficient HVAC system, you don't have to know how each ratio or rating is calculated. What you need to know is how each ratio or rating compares from one type of unit to the next. It's like comparing MPG (Miles Per Gallon) ratings on vehicles. You want to know how many miles per gallon of gasoline each vehicle gets compared to the next. The same is true how one type of HVAC system compares to the next. Basically, the higher the number from the standard rating the more energy-efficient the HVAC unit. The standard rating is determined by the U.S. Department of Energy (DOE). The current energy and water conservation standards from the DOE can be found here.
What am I going to get by purchasing a high-efficiency HVAC system?
So what does this mean to you as a consumer purchasing a new HVAC system? What did you think we were going to say? Nothing!? Everything!? The answer is exactly what your reaction to the question would be. If you answered "I don't know.", you are willing to learn about the benefits of high-efficiency HVAC systems compared to standard systems. If you answered "It doesn't matter.", there is a reason behind your answer. Inital price? Price vs. payback? Not planning to stay in the home? Satisfied with the old system or type you used to have? Whatever the reason, there be will those who will not change their mind about the subject...and that's okay. For those who want to know more, there are many benefits to having a high-efficient HVAC system. Some benefits are:
A. Better indoor air quality with variable speed motors.
B. Start saving money from the beginning.
D. Easily integrated with new technologies like smart thermostats, air filtration, ERVs, ultraviolet purifiers, and other HVAC add-on products.
E. Helping the environment, and reducing your carbon footprint.
F. Less noise (Much less!) with both indoor and outdoor units.
If you need to explain it in one phrase it would be: "Peace of mind." HVAC technology has rapidly evolved in the past 20 years and is still ever-changing. With new environmental laws for older refrigerants, rising electrical and fuel prices, noise and indoor air quality concerns, high-efficiency HVAC is on the right path for a more comfortable, healthier, and greener tomorrow. For the long run.
You can add a geothermal heat pump on a high-efficiency gas furnace.
HVAC Efficiency Terms
AFUE (Annual Fuel Utilization Efficiency)
A furnace and boiler rating for how efficient each unit uses fuel (gas or oil) compared to the amount of actual heat being produced. For example, we could say a 95% AFUE rated gas furnace will generate heat on 95% of all burned gas being produced, 5% will be expelled out the flue or chimney.
CAE (Combined Annual Efficiency)
A measurement for the amount heat being generated for every U.S. dollar ($), or regional currency (€, £, etc.), spent on the type of fuel (gas, oil, electric).
COP (Coefficient Of Performance)
Performance rating for how effective a heat pump or air conditioning unit is at moving heat (work) compared to the amount of electrical energy it used to achieve that amount. COP ratings are mostly used for air source heat pumps over 60,000 Btu/h (5 tons), and more specifically geothermal heat pumps. The higher the COP rating, the more cost efficient the system is to operate.
EER (Energy Efficiency Ratio)
Simular to SEER, this ratio is used only for air conditioning systems. EER is a measurement of efficiency when an air conditioner operates at the specific temperature of 95° F or 35° C. It is calculated using operating outputs (Btu/h), and the average watts of electricity being used during peak cooling conditions. The higher the rating, from the standard DOE rating, the less electricity is being used for the same operating outputs at peak temperatures.
HSPF (Heating Seasonal Performance Factor)
This measurement is used mostly for factoring the efficiency of heat pump systems. An air-source heat pump uses its condenser (outdoor unit) as a primary heating source, but has supplementary electric heaters in the indoor unit. These electrically-staged heaters are used as a secondary heat source when the heat pump starts losing its efficiency at lower outdoor temperatures. HSPF is the total heating output of a heat pump during a typical heating season compared to the total amount of electricity (watt-hours) consumed to produce that same output.
HERS (Home Energy Rating Systems)
An energy rating for buildings (mostly homes) that evaluates its energy efficiencies verses similarly built, less-efficient buildings. This national program is used by builders and lending institutions as an energy quality standard. It gives sellers and buyers an evaluation of how energy efficient the same building is to a comparable standard one.
SEER (Seasonal Energy Efficiency Ratio)
Annual or seasonal efficiency rating, used for heat pumps and air conditioning units, to measure the amount of electrical energy (watt-hour of electricity) used in a typical heating and/or cooling season. Heat pumps are rated for both heating and cooling seasons. Air conditioners are only rated for cooling seasons. This rating takes in account for the size of the unit, average usage per season, variations in temperature, and the average cost per kilowatt of electricity.