Energy Efficiency Explained

How to measure Energy Efficiency

Heating and Air Conditioning systems are measured in British Thermal Units per Hour (BTUh). The heat extracted from your home by an air conditioner is measured in BTUs, while cooling and heating capacities are referred to in British Thermal Units per hour. For reference, 12,000 BTUh equals one ton of cooling.


Home Energy Rating System (HERS)

The Home Energy Rating System (HERS) Index is the INDUSTRY STANDARD by which a home’s energy efficiency is measured. It’s also the NATIONALLY RECOGNIZED system for inspecting and calculating a home’s energy performance. See the HERS system explained here:

energy-star-logoEnergy Star

ENERGY STAR is a government-backed program helping businesses and individuals reduce energy costs and protect the environment through superior energy efficiency.

ENERGY STAR is a voluntary labeling program developed by the U.S. Department of Energy and the Environmental Protection Agency (EPA) in 1992 to promote awareness of energy-efficient products. Manufacturers partner with the EPA to label  high-efficiency systems with the ENERGY STAR label so homeowners can easily identify those higher-efficiency products that can help reduce greenhouse gas emissions and save energy.

The minimum efficiency required by the EPA for ENERGY STAR recognition includes: air conditioner and heat pump units with a SEER of 14.5 or above, 12 EER, or HSPF of 8.2 or above.

SEER stands for Seasonal Energy Efficiency Ratio

The Seasonal Energy Efficiency Ratio (SEER) measures air conditioning and heat pump cooling efficiency, which is calculated by the cooling output for a typical cooling season divided by the total electric energy input during the same time frame. A higher SEER rating means greater energy efficiency.

EER stands for Energy Efficiency Ratio

Like SEER, the Energy Efficiency Ratio (EER) of a cooling unit is determined by the output cooling divided by the electrical power input. As opposed to SEER which is calculated over a range of outside temperatures, EER is typically determined by a set outside air temperature, a set inside air temperature and a 50% relative humidity. For a comparison point, 11 EER is roughly equivalent to 13 SEER.

HSPF stands for Heating Seasonal Performance Factor

The Heating Seasonal Performance Factor (HSPF) is used to measure the efficiency of heat pump. The HSPF is a ratio of the heat output to electricity use over an average heating season, and the higher the HSPF the greater the energy efficiency.

AFUE stands for Annual Fuel Utilization Efficiency

The Annual Fuel Utilization Efficiency (AFUE) is a measure of a gas furnace’s efficiency in converting fuel to energy, by projecting the average thermal efficiency for a complete heating season. A higher AFUE rating means greater energy efficiency.