Evaporative coolers, also known as swamp coolers, are environmentally friendly, cost-effective ways to make your home and outdoor areas more comfortable. These clever appliances draw warm, dry air across water-moistened pads that are fed by either small reservoirs in the machine or, for larger units, drawn from a building’s water supply. This causes the water to evaporate, cooling the air. A fan blows it throughout the space. It’s like misting a room, but more refined and without the soggy mess. A good evaporative cooler, used correctly, can lower temperatures by up to 15 degrees.

When shopping for an evaporative cooler, you’ll want to consider a number of factors. Water tank capacity determines how long the unit will cool; without water, these are just fans. Next, think about cooling area, which is measured in CFM (cubic feet per minute). The higher the CFM, the larger the area it can cool. You’ll also want to consider the unit’s size, and whether it’ll fit in your space. Finally, look at the unit’s energy usage—lower numbers equal better savings on your electricity bill.

Evaporative coolers work best with warm, dry air, so they’re not for everyone. If your environment’s relative humidity is greater than 60 percent, you’re probably better off considering home or in-window air-conditioners. But if you’re in the western part of the U.S., for instance, these indoor/outdoor cooling systems provide an effective way to beat the heat.

7.9-gallon water tank. Amazon

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Honeywell’s midsize evaporative cooler is perfect for dropping the temperature in a mid-size room. It has a CFM of 525, and is rated for 320 square feet. The three fan speeds and separate oscillation settings help distribute cool air throughout the room, and a remote control means you never have to leave the comfort of your couch to adjust the settings. An ice compartment above it’s 7.9-gallon, manually-filled water tank aids in cooling. The CL30XCWW runs for a reported seven-and-half hours, and consumes 288 watts of electricity. If you need to cool off different rooms throughout the day—let’s say you start in a home office and then set up out to the garage—the 33-inch-tall, 25-pound rolling unit isn’t difficult to move.

Cools 850 square feet. Amazon

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This large unit from Honeywell is designed to cool 850 square feet, and is perfect for decks, patios, or any outdoor entertainment spot. It can run all day thanks to a hose-attachment that provides continuous water, while a top-loading ice compartment with overflow tray aids in temperature control. The unit works indoors as well thanks to a 15.9-gallon internal tank. The 41-pound unit isn’t light—and a full water tank only adds to the weight—but casters make it easier to move from space to space.

Be more comfortable in your home. Amazon

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The sleekly designed EC111B looks less like an industrial unit and more like a home appliance. It doesn’t sacrifice substance for style, though; it can cool a 250 square-foot room, drawing water from a 1.8-gallon tank, and it has an ice tray for added temperature control. The oscillating fan provides even coverage throughout the space, and three fan speeds let you customize your comfort level. It has a 7.5-hour timer and remote control for added convenience. It only weighs 16 pounds (without water), and casters make it easy to roll the cooler from room to room.

Colorful LED light. Amazon

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This tiny, desk-top cooler is meant for up-close and personal use. It only holds about .11 gallons of water, but its four-hour cooling time will keep you comfortable while getting some office work done, watching TV, or reading a book. A three-speed fan provides control over cooling. A fun little feature is the seven-color internal LED which allows you to customize the unit’s look or use it as a nightlight. The Vosarea only weighs 1.3 pounds, making it easy to take with you throughout the day.