Evaporative vs refrigerated air

Swamp cooler or AC, in this valley?

In Grand Junction an evaporative cooler handles most hot days well, because the air is usually dry: NOAA normals put June at 22.8 percent average humidity, the driest month of the year. Refrigerated air copes better with humid, stormy late-summer days, and runs with the house closed. July and August average about 34 and 34.2 percent.

Request service Check today with the cooling potential tool

1Hot, dry outside air is pulled into the cooler through its side pads.
2Water soaks the pads A small pump keeps them wet. As water evaporates, it takes heat from the air.
3Cooler, moister air is blown down a short duct into the house.
4An open window lets that air leave. With the house shut, the cooler cannot push air in.

Side by side

How they differ

Evaporative column from Department of Energy guidance. The refrigerated column is general description, not a product claim.

	Evaporative (swamp) cooler	Refrigerated air
How it cools	Evaporates water into outside air, which lowers its temperature. Direct coolers can lower air temperature 15 F to 40 F.	A refrigerant cycle pulls heat out of indoor air and dumps it outside.
Windows	Some must be open. The air passes through the house and has to leave.	Works with the house closed.
Humidity	Adds moisture. Works best when the air is hot and dry; struggles on humid days.	Removes some moisture as it cools.
Energy	The Department of Energy says about one quarter as much as central air conditioning.	More electricity for the same cooling in dry air.
Water	Uses water. The Department of Energy says to count water costs. See the water-use explainer.	No water for cooling.
Outside air	Brings outside air in, so outdoor dust or smoke comes with it. Switch it off on smoky days.	Recirculates indoor air.
Upkeep	Regular maintenance: pads, pan, pump, and a spring startup and fall shutdown.	Filter changes and periodic service.

Month by month

The local numbers

NOAA 1991 to 2020 normals for the Grand Junction airport, warm months only.

Average relative humidity (%)

Days at 90 F or more

NOAA 1991 to 2020 monthly normals, Grand Junction Walker Field (NOAA station USW00023066)
Month	Avg high F	Avg low F	Days 90 F+	Avg humidity %	Cooling degree days
April	65.8	38.1	0	35.2	2.9
May	76.8	47.1	1.9	27.8	55.8
June	89.2	56.8	16.3	22.8	257.4
July	94.5	63.9	25.6	34	440.4
August	90.9	61.6	19.8	34.2	349.9
September	81.7	52.5	4.2	38.3	121.6
October	66.9	39.5	0	50.6	4.9

NOAA 1991 to 2020 normals for Grand Junction Walker Field (NOAA station USW00023066). Long-run averages, not a forecast. Humidity is the monthly average, nights included.

Questions

Common questions

Is a swamp cooler enough for Grand Junction?

For most of the season, many homes find it is: the Department of Energy says evaporative coolers work well where air is hot and dry, and June averages 22.8 percent humidity here. July and August average about 34 percent, so expect some sticky days when it struggles.

Can I run a swamp cooler and AC together?

Not at the same time in the same rooms: the cooler needs open windows and adds moisture, and air conditioning needs the house closed. Some homes use each for different conditions. Ask an HVAC contractor about controls and ducts.

Which is cheaper to run?

The Department of Energy says evaporative coolers can use about one quarter of the energy of central air conditioning, but they use water, and that cost should be counted too. Your rates decide the dollars.

Sources

Read or re-read on 2026-11-06 MT. Each line says what the source backs on this page.

Energy Saver Guide: Tips on saving money and energy in your home (2022), U.S. Department of Energy. Evaporative coolers cool outdoor air with evaporated water, push warmer air out through windows, and work well where the air is hot and humidity is low.
Building America Best Practices: Energy Renovations, HVAC (2011), U.S. Department of Energy, prepared by PNNL and ORNL. Evaporative coolers can use about one quarter as much energy as central air conditioners; direct coolers can lower air temperature 15 F to 40 F; a window or vent must be open; at least two speeds and a vent-only option are recommended; they need regular maintenance; water costs should be counted.
U.S. Climate Normals, 1991 to 2020, NOAA National Centers for Environmental Information. Monthly normals for station USW00023066, Grand Junction Walker Field: average highs and lows, cooling degree days, days at 90 F or above, and relative humidity.
Grand Junction, CO climate data (CSV), PlainClimate, CC0, citing NOAA NCEI. The machine-readable copy of the NOAA 1991 to 2020 monthly normals used in the tables and tools on this site.
Grand Junction station digest, National Weather Service, Grand Junction. Describes a semi-arid climate with about 9.42 inches of precipitation a year, an average of 64.5 days a year at 90 F or above and 6.5 days at 100 F or more.

Keep the cooler, or price a new one

Send a repair or replacement request. For refrigerated air, ask an HVAC contractor for a separate quote.

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