Indoor air can be two to five times as dirty as outside air, so it makes sense that interest in air purifiers spikes in winter, when cold weather keeps us indoors with the windows shut. But we’re just as likely to be shuttered inside in hot weather with the air conditioner cranking. To clear the air, more and more consumers are turning to air purifiers, according to Gfk, a market research firm. But unless you have allergies, you probably don’t need one, and the Environmental Protection Agency does not endorse manufacturer claims of healthier indoor air resulting from the use of air purifiers.

Norman Edelman, M.D., a professor of preventive and internal medicine at New York's Stony Brook University, agrees that keeping indoor air clean is the best strategy but adds that it can be difficult to keep all allergens and particulates out of the house. "The data on air purifiers are not clear," he says. "When used properly, they have been shown to modestly reduce allergy symptoms."

Air purifiers aren’t cheap and can be expensive to operate since they typically run around-the-clock (see chart below). And they have limitations in terms of their primary job. For example, an air purifier can only remove airborne particles, not the dust and pet dander that’s already settled into the carpet. For that you’ll need a good vacuum, says Dave Trezza who has tested both appliances for Consumer Reports.

Finally, our tests found that air purifiers can be noisy, especially at higher speeds, and may keep you awake if you use one in your bedroom.

Still, if you’re convinced you need an air purifier, there are ways to spend less and get capable air-cleaning performance. Start by buying an Energy Star model, which is 40 percent more energy-efficient than a standard model and costs $30 a year less to run. Then check how well the air purifiers in our tests remove smoke, pollen, and dust on both high and low speeds (important for noise).

Our top performer is the Blueair Blue Pure 211, $250. It was excellent at removing fine clay dust and cigarette smoke from the air on both low and high settings. Models that score well for dust are also good at removing pollen, which is roughly the same size. However, in our tests the Blueair Blue Pure was fairly noisy on high (a little less so on low). That’s typical. “We recommend buying a larger air purifier and running it on a slower speed for the best and quietest results,” says Trezza.

The Blueair, like the other four air purifiers CR recommends, is suitable for a 350 to 650 square feet space—a fairly large room. We calculated how much it costs to run each model for one and five years. Annual energy cost is based on running the unit 24 hours a day. Filter costs are based on the manufacturer’s replacement recommendation—typically once or twice a year, or four times a year for carbon filters. Here are the operating costs of our five top models.

That Air Will Cost You

ModelPriceAnnual Energy CostFilter CostTotal/First YearTotal/Fifth Year
Blueair Blue Pure 211$250$51$120$421$1,105
Honeywell HPA300$250$76$127$453$1,265
Honeywell 50250$160$151$62$373$1,225
Sharp Plasmacluster Ion FP-A80U$280$52$130$462$1,190
Idylis AC-2118$250$31$90$371$855

We'd Like to Clear the Air

Even if you use an air purifier, it pays to take a few simple steps to keep indoor air irritants to a minimum:

  • Vacuum often and thoroughly, especially if you have a pet.
  • Ban smoking indoors.
  • Skip the scented candles and fires in the fireplace.
  • Change the filters on your forced air heating and cooling system.
  • Run exhaust fans in the kitchen and bathroom.
  • Keep chemicals, solvents, glues, and pesticides away from living areas.
  • If you need to keep the windows closed to avoid pollen, run the fan of your air conditioner with a clean air filter.