Evaporative cooler vs standard AC for greenhouse
 

So my 15 year old Champion swamp cooler bit the dust (fan OK but pump motor corroded and lifeless, not to mention corrosion thoughout basin) and I need a replacement cooling device. I have a 13 x 8 foot greenhouse and live in Pasadena,CA climate zone 9B/10A. It is usually dry in the summer but lately (?climate change?) humidity has not bottomed out as often lately. A traditional refrigerant type AC would pull 6 amps, about the same as a replacement swamp cooler, and less expensive to install. I'm able to maintain adequate humidity during dry spells - 35% is the lowest daytime (maybe 10 days during hottest driest summer days) but never below 70% evening and over 70% most of the time. Would a traditional window AC unit be viable or just a rusted wall decoration in 3 years? There are almost no web posts I can find which are trustworthy. Thanks!

I couldn’t imagine that a good quality window AC would corrode that fast, but if you don’t get an answer from people here (highly unlikely given the depth and breadth of the combined knowledge held by members) you could always call the company of a brand you’re considering and ask to speak with someone in the technical/engineering department. We had to do that a lot at my last job because our greenhouse operation was very small scale and the nonprofit aspect limited our funding, so we got creative.

You'll have a difficult time maintaining humidity with an A/C unit. The cool air produced has very low humidity.

In Arizona evaporative coolers are very much less expensive to run than A/C units, and I think we have cheaper electricity.

I can't imagine you'll get the same amount of cooling with an A/C for the same electrical consumption unless you have really high humidity.

The pump is very easy to replace. Most can be bought online. Find your cooler model number on a small label on the back or the inside. The company probably has a diagram online showing the parts with their part numbers. If they don't have replacements, search on the pump part number. You will probably find it. Many people repair their own coolers on a regular basis.