How effective are swamp coolers in the Denver area?

As an alternative to a traditional air conditioning system, a swamp cooler uses the process of evaporation to provide cooling comfort. Swamp coolers are energy efficient and can lower an area’s ambient temperature by several degrees.
How a swamp cooler works:
The process is simple: when water evaporates, a large amount of heat from surroundings is absorbed. This is easily observed when you splash water onto your skin on a hot day, as this results in a cooling – almost chilling – sensation because of the rapid evaporation of moisture on the skin.
A swamp cooler is energy-efficient and an affordable cooling devices but they only work well in certain areas where there is low humidity. When the humidity level hits 30% l swamp coolers are going to slow up their cooling capacity, and when you hit 35% they basically stop cooling. On humid days l when there is already a lot of water in the air, you may think that you’re swamp cooler is broken as it’s blowing in warm air.
Swamp coolers become inefficient when it becomes too humid. In Denver, Colorado this begins to happen in July when the summer monsoon kicks in and the days are long and hot. That’s when the humidity begins to climb. Air conditioning is the only thing that works when you have humid days.
The best solution in Denver is to have an efficient air conditioning unit installed so that you can stay cool all summer long and not just in June and September.
Evaporative coolers cost about half as much to install as a central air conditioner but they are only guaranteed for five years. High efficiency HVAC systems last up to four times as long as a swamp cooler. Evaporative coolers have to be cleaned and drained regularly to avoid sediment build up. Otaherwise they can smell and cause roof damage.
The more a swamp cooler runs, the more maintenance it needs. In hot summers, where the cooler operates most of the time, the pads, filters, reservoir, and pump will need to be maintained at least once a month. Air conditioning systems need regular filter changes and yearly preventive maintenance to perform perfectly for years.
Swamp coolers drain through the ductwork into your house, distributing moist air into your living spaces. Moisture often leads to mold and odors. Upholstery can trap those smells. This air can eventually lead to respiratory problems like allergies or asthma.
The moisture in the ductwork causes it to break down over time, pushing metal particles out of the vents and into your home. Refrigerated air systems automatically clean and filter the air, providing a healthy clean cooling solution!

The chart below provides an approximation of temperature changes delivered by a swamp cooler: