Types of Swamp Coolers: Whole-House, Window, Portable, Indirect and Two-Stage

Every swamp cooler does the same basic job: it pulls hot, dry outdoor air through wet pads, lets water evaporate into that air, and blows the cooled result into your space. What differs between types is where the cooler sits, how much air it can move, whether the air it delivers carries the added moisture, and how much installation it needs. Those differences decide whether a unit cools a whole 1,800 sq ft house or just the chair you are sitting in.

This guide sorts the market into the categories that actually matter when you shop, with the airflow, cost and water figures you need to compare them. If you are new to the physics, start with how evaporative coolers work, then come back here.

The five main types at a glance

Most products fit one of five categories. Within the fixed whole-house group there are two mounting styles (downdraft and side-draft), and nearly every type can be built with either aspen or rigid media pads.

Prices vary by region, dealer and season, and installation for fixed units is extra. For installed totals see what a swamp cooler costs.

Whole-house fixed coolers

Fixed coolers are the classic Southwest rooftop box: a galvanized steel or polymer cabinet with pads on three or four sides, a centrifugal blower wheel in the middle, a belt-driven or direct-drive motor (usually two-speed), a small recirculating pump, and a water distribution system (spider/distributor tubes or a trough) that wets the pads from the top. A float valve keeps the reservoir topped up and a bleed-off line or purge pump dumps some water to limit mineral buildup.

These are the only evaporative units with enough airflow to cool a whole house. A typical residential unit is rated somewhere between 3,000 and 7,000 CFM, and larger models are available for big homes or light commercial use. They connect to the house either through a single ceiling diffuser or through a duct system feeding multiple registers.

Downdraft

A downdraft cooler sits on the roof and blows straight down through a roof curb into a short duct and a ceiling diffuser or attic duct system. Short duct runs mean less airflow loss, and central placement spreads air well in single-story homes. The trade-offs are roof penetration (a potential leak point), a roof that has to carry the operating weight, and service done on a ladder or on the roof.

Side-draft

A side-draft cooler discharges horizontally. It may sit on a ground stand and push air through a wall opening, or sit on the roof and turn down into the house through a duct elbow. Ground-mounted side-drafts are easier and safer to service and avoid roof leaks. A related ground-mounted style, the updraft cooler, discharges upward into a duct that rises into the attic and feeds ceiling registers.

The detailed trade-offs, including a decision table by house type, are in downdraft vs side-draft coolers.

Window coolers

A window evaporative cooler is a smaller fixed unit that mounts in or through a window opening, with the cabinet outside and a grille facing the room. Most are built like miniature side-draft coolers, with aspen or rigid pads, a pump, a float or simple fill, and a fan. Airflow is typically in the 2,000 to 4,500 CFM range, enough for one large room or a few connected rooms.

Window units make sense for renters who cannot cut a roof, for adding cooling to a bedroom wing or garage conversion, and for mobile homes. They do need a support bracket, a water line or a reliable manual fill, and an open window elsewhere for relief air. See window evaporative coolers for fit and model selection.

Portable coolers

Portable evaporative coolers are self-contained units on casters with a built-in water tank. Residential models range from slim tower units moving a few hundred CFM to box-style units around 1,000 to 1,500 CFM. Commercial and outdoor portables are much larger, with fans that can move tens of thousands of CFM and tanks measured in tens of gallons.

Two realities shape portables. First, airflow is modest, so in practice they are spot coolers: you feel cool air in front of the unit, while the far side of the room barely changes. Second, they need relief air just like fixed units; run one in a closed room and the humidity climbs until cooling nearly stops. The portable evaporative cooler buying guide covers tank size, pad type and what spec sheet claims really mean, and sizing portable and outdoor coolers shows how to match one to a room, garage or patio.

Indirect and two-stage coolers

A direct cooler puts air in contact with water, so the air leaving it is cooler and more humid. An indirect cooler runs outdoor air through a heat exchanger: water evaporates on one side (the wet or secondary air path, which is exhausted outdoors), and the house air passes through dry channels on the other side and is cooled without gaining moisture. Indirect units alone usually cannot get as cold as a good direct cooler, but they add no humidity to the house.

A two-stage, or indirect-direct, cooler stacks the two: the indirect stage pre-cools the air, then a direct stage cools it further. Because the direct stage now starts from a lower dry bulb and wet bulb, the supply air can end up cooler than a direct cooler alone could achieve, and it carries less added moisture per degree of cooling. These units cost more, use more fan energy, and are less common in residential settings, but they extend comfortable evaporative cooling into climates with moderate humidity. The mechanism is explained in direct vs indirect evaporative cooling.

Pad media: the hidden "type" inside every cooler

Within each cabinet style, the pad type changes performance more than most shoppers expect. Supply air temperature follows a simple relationship:

Aspen (wood fiber) pads usually reach roughly 60 to 80% saturation efficiency. Rigid cross-fluted cellulose media, such as 8 in thick panels, reach roughly 85 to 90%, and 12 in rigid media can reach about 90 to 95%.

Rigid media costs more up front but typically lasts several seasons, while aspen pads are cheap and usually replaced every season or two. Details are in aspen vs rigid media.

Which type fits your situation

Use this as a starting point, then confirm the climate side with the climate index.

Climate limits apply to every type

No cabinet design gets around the wet bulb. When outdoor wet bulb temperatures rise into the upper 60s and 70s F, a direct cooler's supply air is warm and humid, and comfort drops off no matter how much you spent. That is why evaporative cooling dominates in places like Phoenix, Las Vegas, Albuquerque and Denver and is rare in humid regions. During the monsoon months in the desert Southwest, even good units struggle on muggy days; see do swamp coolers work in humidity.

Once you have picked a type, the next step is airflow. A cooler that is the right style but too small for the house will run flat out and still lose the afternoon. Work through how to size a swamp cooler or plug your numbers into the cooler size calculator.