Standards for “cooling choice of last resort” will slash energy waste

Posted on by
Joanna Mauer

On December 28, 2016, the US Department of Energy (DOE) issued the first-ever energy efficiency standards for portable air conditioners (ACs). The new standards will reduce energy use more than 20% relative to the least-efficient products available today and provide large savings for consumers.

DOE estimates that more than one million portable ACs are sold each year. Consumer Reports has referred to portable ACs as “the cooling choice of last resort” and found in their tests that portable ACs “barely got a room below sweltering.”

Portable ACs are similar to window AC units, except instead of being mounted in a window, portable ACs sit on the floor and exhaust hot air through a window using a duct. The problem with portable ACs sold today is that much or all of the air flow used to reject heat to the outside is drawn from the room being cooled. This process creates a negative pressure, which results in hot air being drawn in from outside. Making matters worse, portable ACs also add heat to the room due to heat losses through the duct and the unit’s case.

While window ACs have been subject to efficiency standards for more than 25 years, portable ACs have never had to meet any efficiency requirements. As a result, their efficiency performance has lagged badly.

DOE estimates that typical portable ACs sold today use about 900 kilowatt-hours (kWh) per year, which is roughly twice what a typical new window AC uses. While portable ACs will likely continue to provide subpar cooling performance, the new standards will cut energy waste. The standards can be met using more-efficient compressors and improved heat exchangers.

DOE estimates that with the new standards consumers will save $125 on average over the lifetime of a portable AC unit. On a national level, the new standards will save about 50 billion kWh over 30 years of sales, which is equivalent to the annual electricity use of about 4 million US households. Over the same period consumers will save $1-3 billion.

Even greater savings are possible. DOE evaluated higher efficiency levels that would reduce energy use by about 35-45%, but did not adopt these higher levels due to concerns about potential manufacturer impacts and product availability.

Along with the new standards for portable ACs, consumers will also have much better information for making purchasing decisions. Previously, the advertised cooling capacities and efficiencies of portable ACs were not based on a standardized test method, and they often significantly overestimated actual performance. This discrepancy between rated values and actual performance made it difficult for consumers to compare units. Manufacturers are now required to use standardized rating methods for determining cooling capacity and efficiency, which will enable easy comparison of different portable AC units.

The new standards for portable ACs will take effect 5 years after publication in the Federal Register.

Note: This new standard will not be officially final until published in the Federal Register. Most likely, final publication will be decided by the Trump administration.