Lennox Commercial

Efficiency Ratings

Measuring efficiency in HVAC systems helps compare the effectiveness of different units in an easy and equitable manner. Depending on the system and application, there are several methods to measure efficiency, providing useful information. Among the most common efficiency measurements are Annualized Fuel Utilization Efficiency (AFUE); Cooling Capacity; Seasonal Energy Efficiency Ratio (SEER); Energy Efficiency Ratio (EER); and Integrated Energy Efficiency Ratio (IEER).


Annualized Fuel Utilization Efficiency is the fuel efficiency rating for warm-air, gas or oil-fired furnaces less than 150,000 Btuh. The higher the AFUE, the more efficient the furnace. The minimum percentage established by the Department of Energy (DOE) for furnaces is 78%.

Cooling Capacity

The cooling output of an air conditioner.

Seasonal Energy Efficiency Ratio (SEER)

This is the cooling output provided by the unit during its normal annual usage period, divided by its total energy consumption. The higher the SEER rating, the more energy-efficient the system. Rating is only applicable to units under 6 tons (65,000 BTU/H).

Energy Efficiency Ratio (EER)

This measures the cooling output of a unit divided by its total energy consumption, measured during continuous operation at a given operating condition (95 degrees or full load).

Integrated Energy Efficiency Ratio (IEER)

This measure expresses cooling part-load EER efficiency for commercial unitary air conditioning and heat pump equipment on the basis of weighted operation at various load capacities. Previously known as IPLV.

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