Swamp Cooler vs Air Conditioner in Colorado: What Actually Works Here

By the team at Homegrown Heating and Air Conditioning.

The swamp cooler vs air conditioner question in Colorado has a real answer. Evaporative cooling works here because of one property of Front Range air, and it stops working on the days that property goes away. Here is what governs the decision, what each system costs to run, and how to tell which one belongs on your house.

How a Swamp Cooler Actually Cools a House

A swamp cooler does not make cold. It trades heat for evaporation.

Outdoor air is pulled through wet pads. Liquid water turns to vapor, and the energy required for that change of state is taken out of the air itself. The air leaves the pads cooler and wetter than it arrived. Its total heat content barely moves. Engineers call this adiabatic saturation, and it is the whole machine.

That single mechanism sets a hard ceiling on performance. How far the temperature can drop depends entirely on the wet bulb depression, which is the gap between the dry bulb temperature an ordinary thermometer reads and the wet bulb temperature the same thermometer reads with a wet sleeve over the sensor. Dry air has a wide gap. Saturated air has none at all.

A cooler can capture most of that gap. It can never exceed it.

This is why the same appliance is standard equipment in Northern Colorado and worthless on the Gulf Coast. Our summer afternoons combine high dry bulb temperatures with low moisture content, which is a wide wet bulb depression and a large amount of cooling available for the cost of running a fan and a pump. The Department of Energy guidance on evaporative coolers puts the achievable drop at 15 to 40 degrees F in low humidity areas, and notes plainly that these units are only suitable for areas with low humidity.

It also explains the installed base. Fort Collins runs 569 cooling degree days against 5,918 heating degree days. A short, dry, sharp cooling season is what filled older neighborhoods with rooftop evaporative equipment.

The Limit Nobody Mentions Until August

Here is the part that gets left out of most comparisons: a swamp cooler loses capacity precisely on the days you want it most.

Late July and August on the Front Range bring monsoon moisture up from the south. Dew points climb, afternoon storms build, and the wet bulb depression narrows. The cooler is still running. It is still using water and power. It is simply delivering less temperature drop, because there is less gap left to work with.

Homeowners read that as a broken cooler and call for service. Usually nothing is broken. The pads are wet, the pump is fine, and the machine is doing everything the physics allows that afternoon.

Two things get worse at once. The incoming air already carries more moisture, so indoor humidity climbs faster. And the cooler cannot remove any of it: evaporative cooling adds water by design, with no coil, no condensate drain and no ability to dehumidify.

If your complaint is that the house feels muggy rather than hot, that is not a repair. That is the equipment telling you what it is.

What a Swamp Cooler Requires to Work at All

A swamp cooler is a once-through machine. It pushes outdoor air in, and that air has to leave somewhere.

Windows or relief vents must stay partly open, and the amount matters. Open too little and humidity builds indoors. Open too much and hot outdoor air short circuits the effect. Refrigerated air conditioning does the opposite and recirculates indoor air behind closed windows.

That difference reaches past comfort. An open house in August is an open house during wildfire smoke season in Larimer and Weld counties, and a swamp cooler has no filtration path worth the name. If smoke is a recurring problem at your address, it belongs in this decision alongside temperature, and our indoor air quality work starts from the same premise.

Swamp Cooler vs Air Conditioner in Colorado: Running Costs and Upkeep

On pure operating cost, evaporative cooling wins and it is not close. The Department of Energy puts installation at about half the cost of central air conditioning and energy use at about one quarter. A fan and a small pump draw far less than a compressor. The costs that get underestimated are water and labor.

Factor	Evaporative cooler	Refrigerated air conditioning
Installed cost	About half that of central AC	Baseline
Energy use	About one quarter that of central AC	Baseline
Water use	Continuous whenever it runs	None
Windows	Must stay partly open	Stay closed
Indoor humidity	Adds moisture	Removes moisture
Performance on humid days	Drops off	Unchanged
Seasonal work	Startup and shutdown every year, pads replaced	Filter changes and annual service

That last row is the one homeowners forget. A swamp cooler is commissioned each spring and winterized each fall: water line charged, then drained and blown clear, pads inspected, reservoir cleaned of scale. Skip the fall shutdown once at 5,000 feet and you buy a split supply line.

Pads are consumable. The Department of Energy recommends replacing them at least twice per cooling season, or monthly under continuous operation, plus a full drain and clean every season.

The Rebate Situation Is Backwards From What People Expect

This surprises people every summer.

• Poudre Valley REA still pays a $200 rebate on an evaporative cooler, plus $100 on a whole house fan, for members in Wellington, Laporte, Timnath, Berthoud and parts of Windsor.
• Xcel Energy also still carries an evaporative cooler rebate.
• Xcel central air conditioning rebates are gone. They have not been available for invoices dated after January 1, 2024.

The lower cost option is the one still being subsidized. Rebate programs change on their own schedule, so treat these as accurate for the 2026 season.

How to Actually Decide

Neither system is right for every house.

Keep the swamp cooler if your house is one story or compact, you are comfortable with windows open, nobody has a smoke or allergy sensitivity, and the sticky weeks in August are livable.

Convert to refrigerated air if anyone sleeps badly in humidity, you want the house closed and filtered during smoke season, you have a two story layout where open windows fight the stack effect, or you are adding a heat pump.

Run both if the budget allows. Some Northern Colorado homes keep the cooler for June and a refrigerated system for the humid stretch.

We do not push a conversion on a cooler that still works. When conversion is the right call, central AC installation is the path, and we size it from the house rather than from the old equipment.

A Repair Call That Did Not End in a Replacement Quote

Not every cooling visit should end with a proposal. One homeowner called us mid season about an aging air conditioner she assumed was finished. Our technician Steele cleaned it and got the season out of it.

Lauren Campbell wrote: “Steele was great!” She added that he was “able to clean it well enough that it will last through the season” and that he “provided a detailed estimate for a potential replacement.”

That order is deliberate. We fix what can be fixed, we quote replacement as information rather than pressure, and we leave the timing to the homeowner. That holds whether the equipment is a condenser or a rooftop cooler. Read more customer reviews from Northern Colorado homeowners.

Talk It Through Before You Buy Anything

Tell us about the house, the current equipment and what bothers you, and we will tell you which direction fits. Contact Homegrown Heating and Air Conditioning to book an evaluation anywhere in Northern Colorado, seven days a week, 7 a.m. to 7 p.m. We are licensed and insured throughout Northern Colorado.

Questions Northern Colorado Homeowners Ask

At what humidity does a swamp cooler stop working in Northern Colorado?

There is no single cutoff, because performance falls gradually as the wet bulb depression narrows. Homeowners here notice it during the late July and August monsoon stretch, when moisture moves up from the south. The cooler keeps running and delivers a smaller temperature drop.

Can I use a swamp cooler with the windows closed?

No. It has to exhaust the air it brings in, so windows or relief vents stay partly open by design. Closing the house traps the moisture the cooler is adding and the air gets damp rather than cool.

Can I reuse my existing ducts if I convert to central AC?

Sometimes. Evaporative ducts are often sized for much higher airflow at lower static pressure, and the supply layout may have no return path at all. We measure static pressure and duct sizing before quoting, because a conversion dropped onto the wrong duct system underperforms from day one. Our AC repair team sees the results every summer.

Does a swamp cooler help or hurt during wildfire smoke season?

It hurts. The cooler requires open windows and has no meaningful filtration, so it pulls outdoor air and smoke particles directly into the house. Larimer and Weld counties have a long fire history, and the smoke months overlap the weeks evaporative cooling is asked to perform.

Do I need a permit to convert from a swamp cooler to central air?

Usually yes, because the conversion adds refrigerant piping and an electrical circuit. Requirements differ across Fort Collins, Larimer County, Weld County and the individual towns. We pull the permit and handle the inspection as part of the job.

Is evaporative cooling common in Greeley and Loveland specifically?

Yes. Older housing stock across Greeley and north Loveland carries a high share of rooftop evaporative equipment, much of it original to the house. That is where most of our conversion questions come from, and where duct condition varies the most.