Understanding HVAC Energy Efficiency Ratings

When selecting HVAC equipment, you'll encounter various energy efficiency ratings. Understanding these ratings can help you choose systems that save energy and money over their lifespan. Higher ratings generally mean greater efficiency but may come with a higher upfront cost.

SEER (Seasonal Energy Efficiency Ratio)

SEER measures the cooling efficiency of air conditioners and heat pumps over an entire cooling season. It's calculated by dividing the total cooling output (BTUs) by the total electrical energy input (Watt-hours) during that period. A higher SEER rating indicates greater energy efficiency. Minimum SEER requirements are set by governments and vary by region.

EER (Energy Efficiency Ratio)

EER measures cooling efficiency at a single, specific set of outdoor (e.g., 95°F) and indoor (e.g., 80°F, 50% RH) conditions. It's the ratio of cooling capacity (BTU/hr) to power input (Watts) at these fixed conditions. While SEER is generally a better indicator of seasonal performance, EER is useful for comparing performance under peak load conditions. Higher EER means better efficiency at specific peak conditions.

AFUE (Annual Fuel Utilization Efficiency)

AFUE measures the efficiency of furnaces and boilers in converting fuel to heat over a typical heating season. It's expressed as a percentage. For example, an AFUE of 90% means that 90% of the fuel's energy becomes heat for the home, while 10% is lost (e.g., up the flue). A higher AFUE percentage means greater fuel efficiency.

HSPF (Heating Seasonal Performance Factor)

HSPF measures the heating efficiency of air-source heat pumps over an entire heating season. It's calculated by dividing the total heating output (BTUs) by the total electrical energy input (Watt-hours). A higher HSPF rating indicates greater heating efficiency for heat pumps. There's also HSPF2, a newer standard with updated testing procedures.

COP (Coefficient of Performance)

COP is a more general, instantaneous measure of efficiency for heating or cooling equipment. It's the ratio of useful heating or cooling provided (in Watts) to the work (energy input, in Watts) required. For example, a heat pump with a COP of 3 provides 3 units of heat energy for every 1 unit of electrical energy consumed. Higher COP means better efficiency. It can be related to EER and HSPF (e.g., COP_cooling ≈ EER / 3.412).

Note: Always check current minimum efficiency standards in your region and consider lifecycle costs when choosing equipment. Our Efficiency Payback Calculator can help analyze potential savings.