I have an Arizona home built in 1997 with a swamp cooler and an A/C unit. What is the most Energy Efficient way to cool my house?

Asked by Mat Kearney
Phoenix, AZ

I have an Arizona home built in 1997 with a swamp cooler and a A/C unit. I also have ceiling fans in each room. I know I can increase my insulation and add shade trees but I would like how to use my current setup the most efficiently.


Elizabeth DiSalvo

Answered by Elizabeth DiSalvo

Ridgefield , CT

Trillium Architects

August 21, 2012

Hi Mat,

Great question. Here are a few things to remember about Swamp Coolers and traditional AC units:

  1. Swamp coolers are much more efficient than AC units. They can use up to 75% less energy than your AC units, so choose the Swamp Cooler over the AC when possible.
  2. Never use both your AC and your Swamp Cooler at the same time. Due to their different technologies they actually make each other work harder and sort of cancel each other out in some situations. So one at a time.
  3. Swamp Coolers work most effectively during the middle of the day, when it is hottest and driest. The drier the air, the better the efficiency.
  4. If humidity rises above 30% the Swamp Cooler is not an appropriate choice. So, maybe use the AC when it is a bit humid outside (if ever in Arizona!)
  5. When using a Swamp Cooler you want to open a window or two or three. The Swamp Cooler works best with open air flow. You actually get the highest efficiency when windows are open. (The same would NOT be said for AC units which is another reason not to run them at the same time.)
  6. Turn on your ceiling fans when you are using the Swamp Cooler if you like. Swamp Coolers move air. The movement of the air, along with the evaporation of water running through the unit, make the air feel cooler than it actually may be - somewhere around 4-6 degrees cooler. So, the fan just increases the air movement and makes the air feel even cooler, thus using less Swamp Cooler energy to achieve your desired temperature. I would play with this combination - depending on the location of the fans and the flow of air. Use your intuition to see if the fans are helping the flow of air in your house, hindering it or if it seems like unnecessary overkill.
  7. Clean your filters frequently. This will up the efficiency and make the unit last longer and the air smell better.
  8. Swamp Coolers use a lot of water. If you are in drought conditions you may consider using your AC unit instead. It will be more expensive but you will help save water.
  9. You can get higher efficiency, lower water usage coolers. You can also get coolers that will somewhat recycle the used water. Using such coolers and calculating your load/needs properly will ensure you have the most efficient system possible. Also the more efficient systems last longer and need less maintenance.
  10. Check the size of the unit for your house. Proper sizing of your unit can be calculated this way: Multiply your interior floor plan square footage x the height of your interior ceiling to get the volume of air inside your home. Divide this number by 2 and you have the number of CFMs cooling you need. (with the caveat that if you have a super insulated, well shaded, light colored house you will need less cooling) Example: 2,000 sf x 8 feet = 16,000 / 2 = 8,000 CFM unit.
  11. Think about using Solar (Photo Voltaic) panels to provide electrical energy to run your unit. The units do not require huge quantities of energy and can be handled easily by PV. Also the sun is strongest at the times of day when the temperature is highest which is also when the Swamp Cooler works best – so it is sort of a perfect situation.
  12. Lastly, If it is possible, zone your house by shutting doors at night to close off the bedrooms from the living areas or by closing all shades in the bedrooms during the day. This can help use less overall energy. Remember also that exterior shades work much better at cooling than interior shades.

Best of luck with operating your system for optimum efficiency!

And yes of course you are right - shading, reflective or white roofs and walls, and good insulation all help with cooling very significantly. We always encourage our clients to try to optimize these things, but knowing your equipment and how to work it properly is half the battle!

Tagged In: heating cooling

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