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B AC vs evaporative cooler: ratio of (BTUs/hr)/electric watts

  1. Jul 27, 2016 #1

    Air conditioner vs evaporative cooler: ratio of (BTUs/hr) / electrical watts

    I know evaporative coolers do not state BTUs/hr. I do not know why.

    Did anyone try them and record time taken to cool.

    I found this example, but I do not know if it is practically relevant:


    I just read the last line “In this example, the cost of electrical cooling is about 7 times greater than the cost of evaporative cooling.”
  2. jcsd
  3. Jul 27, 2016 #2


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    Gold Member

    Evaporative coolers, aka 'swamp coolers' work in dry air (only). As the humidity increases, evaporation decreases, and the resultant heat removal due to evaporation decreases.

    I imagine it is difficult for manufacturers to make meaningful claims about heat removal for swamp coolers.

    I grew up with a swamp cooler in AZ, it worked great in the dry air. I live in Dallas now, and it would be a waste of electricity here.

    A swamp cooler runs a fan and a small water pump (really small), so it basically uses as much electricity as a fan. Electrical coolers run a high pressure pump that moves freon in a closed system through two phases (gas / liquid), this takes a lot more power than just blowing air past / over wet pads that have water dripping on them, which is what a swamp cooler does.
  4. Jul 27, 2016 #3


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    Staff: Mentor

    Strictly speaking, direct evaporative coolers don't do any cooling, so there's that...

    Griddle is also correct; evaporative cooler output is highly dependent on the input conditions, and therefore very inconsistent. So the vendors don't give general BTU ratings.

    But you coud pick a specific set of conditions and calculate sensible cooling provided. Much of the info can be gotten from a performance table.
  5. Jul 27, 2016 #4
    OK Thanks a lot
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