Air Purifiers and Power Consumption

For many reasons consumers are becoming much more conscientious of energy usage when it comes to household appliances, both large and small. One major reason is personal, to reduce their overall expenses and make their income stretch farther. Another would be more as a social obligation to reduce their carbon footprint on the environment.

This article is written to compare major types and brands of air purifiers to find the balance of cleaning efficiency and lowest possible power usage. As with central air and furnace systems, there is certainly a challenge in moving a house full of air with the least amount of energy. Some of the earliest types of ionic purifiers achieved impressively low power usage while claiming to zap impurities out of the air, both particulate and molecular. Not only were they found to produce unhealthy amounts of ozone, but they were also found to be ineffective at actually cleaning the air. This was partly because the air could not be moved through the unit, since it was not equipped with a fan. So much for a low-power air purifier!

Is it possible to marry the two objectives? Can a high quality HEPA-equipped purifier also use low amounts of energy to move the air necessary for the removal of dust, pollen, smoke or organic particles? In my search for such a purifier that meets these requirements, I found that many units that claim low power usage also sacrifice cleaning efficiency (poor CADR* ratings in comparison with other units). In addition, the comparison of air purifiers based on energy usage at the highest fan settings is not a fair method for discovering the intersect of effectiveness and energy use, because an air purifier rarely needs to be run on high speeds for any length of time.

One helpful resource I found was on the EnergyStar website that gave product comparisons with a specific column labeled as CADR/Watt, which is simply a number representing the amount of cleaning efficiency expressed in the CAD rating per watt of power used to circulate the air (and run any other electronic technologies for the cleaning process). Although dozens of models are not included in the database, it’s easy to see that many manufacturers that claim “low power consumption” do not necessarily have a high CADR/Watt rating. The highest rated unit in this comparison is the Blueair ECO 10 with a score of 19.66, while most rank with a score of 3 or less. Keep in mind that units with a high score may be more air purification than you actually need, and in small, confined spaces the newer and safer ionic-type purifiers with low power consumption (as low as 12 watts) may be adequate. Moving up to medium to large spaces, these technologies lose their efficiency. For these areas, the objective would be to find a unit with a CADR as high as 400, like the Blueair or Airgle, and then narrow these models down by power usage.

* Clean Air Delivery Rate (CADR) is a measure of the appliance’s ability to reduce smoke, dust, and pollen particles in the 0.10 to 11 micron (μm) size range from the air. In ANSI/AHAM AC-1-2006, CADR is defined as “the rate of contaminant reduction in the test chamber when the unit is turned on, minus the rate of natural decay when the unit is not running, multiplied by the volume of the test chamber as measured in cubic feet.” The 1008 ft3 test chamber size is an integral part of the definition and is standardized in ANSI/AHAM AC-1-2006 to ensure that comparisons between units that have been evaluated using the standard are fairly made. This standardized room size chamber limits the maximum CADR measurement (or value) to 450 (pollen and smoke) and 400 (dust). These maximum CADR values were determined through analysis of the acceptable minimum number of available particles, an average background natural decay rate (from statistical study), the size of the chamber, and the available minimum experiment time.