New air conditioner standards will reduce cooling costs for modular classrooms and offices

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Joanna Mauer

New energy efficiency standards for certain types of specialized air conditioners will reduce cooling costs for many schools as well as other buildings. The new standards issued by the US Department of Energy (DOE) last week will cut cooling energy use by about 18% relative to the current standards.

The final rule sets new minimum efficiency levels for single-package vertical air conditioners and heat pumps, which are commonly used to cool modular classrooms and offices and telecommunications shelters housing electronic equipment. These air conditioners are installed on external building walls.

The final rule adopts the efficiency levels that were proposed at the end of last year.

DOE estimates that over the lifetime of units sold over 30 years, the new standards will net customers $110-380 million in savings and reduce electricity consumption by about 16 billion kilowatt-hours (kWh), an amount equal to the annual electricity use of 1.5 million U.S. households.

Vertical heat pumps can reverse the refrigeration cycle to provide heating to schools or offices in the winter in addition to cooling during the summer, while vertical air conditioners can also provide heating using gas or electricity, for example. Unlike schools and offices, telecommunications shelters often require year-round cooling due to the high internal heat load from the electronic equipment housed inside.

DOE estimates that a single vertical air conditioner just meeting the current standards consumes about 6,800 kWh per year on average, while a vertical heat pump consumes more than 20,000 kWh per year. By comparison, an average U.S. household consumes about 11,000 kWh annually.

The cooling efficiency of vertical air conditioners and heat pumps is measured by the energy efficiency ratio (EER), where higher values indicate higher efficiency. The current standards for vertical air conditioners and heat pumps require a minimum EER of 9 for the most common equipment. The latest version of ASHRAE 90.1, a commercial building energy code, specifies a minimum EER of 10 for vertical air conditioners and heat pumps. The new standards will raise the minimum national efficiency level to 11 EER for the most common equipment.

The new standards will take effect in 2019.