# Air conditioner operation in the rain **URL:** \ **Category:** Factual Questions\ **Created:** [August 16, 2016, 12:19pm UTC](https://boards.straightdope.com/t/air-conditioner-operation-in-the-rain/762986 "2016-08-16T12:19:26Z")\ **Posts on this page:** 16\ **Page:** 1
**Author:** ![Cardigan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cardigan/32/187_2.png) [@Cardigan](https://boards.straightdope.com/u/Cardigan)\ **Post date:** [August 16, 2016, 12:19pm UTC](https://boards.straightdope.com/t/air-conditioner-operation-in-the-rain/762986/1 "2016-08-16T12:19:26Z")
It was beastly hot the other day and the humidity was high, so I turned the air conditioner on. Later that day it started raining and my wife said ‘oh, you’d better turn off the a/c because it’s starting to rain and you don’t want to ruin it.’ I can understand turning off the a/c when it rains because that often means the temps cool down, but is there any harm in operating a home air conditioner while it’s raining? Does it damage the unit, expose it to extra corrosion, or reduce its’ service life in any way? ---
**Author:** ![boytyperanma](https://avatars.discourse-cdn.com/v4/letter/b/4491bb/32.png) [@boytyperanma](https://boards.straightdope.com/u/boytyperanma)\ **Post date:** [August 16, 2016, 12:35pm UTC](https://boards.straightdope.com/t/air-conditioner-operation-in-the-rain/762986/2 "2016-08-16T12:35:18Z")
Has no meaningful impact on it. It gets rained on weather you’re running it or not. It’s made with that in mind. I wouldn’t be stopping it for rain, I’d want it running for the humidity. ---
**Author:** ![friedo](https://avatars.discourse-cdn.com/v4/letter/f/8edcca/32.png) [@friedo](https://boards.straightdope.com/u/friedo)\ **Post date:** [August 16, 2016, 12:41pm UTC](https://boards.straightdope.com/t/air-conditioner-operation-in-the-rain/762986/3 "2016-08-16T12:41:20Z")
Rain actually makes the AC run more efficiently. The rainwater will help cool the condenser coils faster than the outside air alone. ---
**Author:** ![TriPolar](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tripolar/32/3008_2.png) [@TriPolar](https://boards.straightdope.com/u/TriPolar)\ **Post date:** [August 16, 2016, 1:01pm UTC](https://boards.straightdope.com/t/air-conditioner-operation-in-the-rain/762986/4 "2016-08-16T13:01:48Z")
> [@friedo](#): > > Rain actually makes the AC run more efficiently. The rainwater will help cool the condenser coils faster than the outside air alone. The rain water doesn’t have to hit the coils, and it may not, but the higher humidity will make it more efficient. I suppose your AC might lose a day or two of it’s life from excess exposure to water but they’re designed for the outer portion to be outside in all sorts of weather conditions. And by dehumidifying your house you’re preserving much more value than the AC costs. ---
**Author:** ![BubbaDog](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bubbadog/32/333_2.png) [@BubbaDog](https://boards.straightdope.com/u/BubbaDog)\ **Post date:** [August 16, 2016, 1:19pm UTC](https://boards.straightdope.com/t/air-conditioner-operation-in-the-rain/762986/5 "2016-08-16T13:19:51Z")
Running in the rain shouldn’t hurt it at all. As others have pointed out it may actually improve its efficiency. I’ve prayed mine with a garden hose on hot dry days just to give it a little boost. I had a neighbor who garden misters next to his and claimed it kept his costs down. ---
**Author:** ![friedo](https://avatars.discourse-cdn.com/v4/letter/f/8edcca/32.png) [@friedo](https://boards.straightdope.com/u/friedo)\ **Post date:** [August 16, 2016, 1:22pm UTC](https://boards.straightdope.com/t/air-conditioner-operation-in-the-rain/762986/6 "2016-08-16T13:22:59Z")
> [@BubbaDog](#): > > I had a neighbor who garden misters next to his and claimed it kept his costs down. Newer air conditioners actually do something similar by maintaining a small reservoir of condensate which they spritz onto the condenser coils as needed. ---
**Author:** ![bump](https://avatars.discourse-cdn.com/v4/letter/b/7c8e57/32.png) [@bump](https://boards.straightdope.com/u/bump)\ **Post date:** [August 16, 2016, 2:10pm UTC](https://boards.straightdope.com/t/air-conditioner-operation-in-the-rain/762986/7 "2016-08-16T14:10:22Z")
> [@friedo](#): > > Rain actually makes the AC run more efficiently. The rainwater will help cool the condenser coils faster than the outside air alone. This. You can sometimes tell when it starts raining, because your house cools down a bit. ---
**Author:** ![Just\_Asking\_Questions](https://avatars.discourse-cdn.com/v4/letter/j/ba9def/32.png) [@Just\_Asking\_Questions](https://boards.straightdope.com/u/Just_Asking_Questions)\ **Post date:** [August 16, 2016, 2:56pm UTC](https://boards.straightdope.com/t/air-conditioner-operation-in-the-rain/762986/8 "2016-08-16T14:56:52Z")
Air conditioner running under water. [Trane commercial.](https://www.ispot.tv/ad/7iQf/trane-boat-drop) I don’t think it survived the boat drop, though. ---
**Author:** ![aceplace57](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/aceplace57/32/3500_2.png) [@aceplace57](https://boards.straightdope.com/u/aceplace57)\ **Post date:** [August 16, 2016, 3:10pm UTC](https://boards.straightdope.com/t/air-conditioner-operation-in-the-rain/762986/9 "2016-08-16T15:10:44Z")
People with central AC run it 24/7 with no thoughts about rainy weather. The thermostat keeps the house at a constant temperature. It runs less on cooler, rainy days. Pollution is the biggest problem. My childhood hometown has several chemical plants. The condenser coils on these units gets very corroded. A close friend of mine is a serviceman and they use acid and a wire bush to scrub off the coil. That’s one of several reasons I no longer live there. Zinc bromide and  liquid calcium chloride are produced there in those plants. ---
**Author:** ![TriPolar](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tripolar/32/3008_2.png) [@TriPolar](https://boards.straightdope.com/u/TriPolar)\ **Post date:** [August 16, 2016, 3:17pm UTC](https://boards.straightdope.com/t/air-conditioner-operation-in-the-rain/762986/10 "2016-08-16T15:17:10Z")
> [@friedo](#): > > Newer air conditioners actually do something similar by maintaining a small reservoir of condensate which they spritz onto the condenser coils as needed. That’s a really good idea. AC efficiency in hot dry weather can be very low. It’s sort of balanced by the lack of humidity, you know, the dry air doesn’t feel as hot, but better thermal conductivity from a little bit of water is going to help. ---
**Author:** ![lazybratsche](https://avatars.discourse-cdn.com/v4/letter/l/ba8739/32.png) [@lazybratsche](https://boards.straightdope.com/u/lazybratsche)\ **Post date:** [August 16, 2016, 3:25pm UTC](https://boards.straightdope.com/t/air-conditioner-operation-in-the-rain/762986/11 "2016-08-16T15:25:32Z")
> [@friedo](#): > > Newer air conditioners actually do something similar by maintaining a small reservoir of condensate which they spritz onto the condenser coils as needed. You make it sound so precisely engineered! On the window AC units I’ve opened up, the condensate drains into a tray under the condensor coils and fan. The fan blades dip into this tray and splash water everywhere. On a hot and humid day, you can hear a constant “sploosh sploosh”. ---
**Author:** ![PlumBob](https://avatars.discourse-cdn.com/v4/letter/p/ee59a6/32.png) [@PlumBob](https://boards.straightdope.com/u/PlumBob)\ **Post date:** [August 16, 2016, 3:42pm UTC](https://boards.straightdope.com/t/air-conditioner-operation-in-the-rain/762986/12 "2016-08-16T15:42:43Z")
> [@lazybratsche](#): > > You make it sound so precisely engineered! On the window AC units I’ve opened up, the condensate drains into a tray under the condensor coils and fan. The fan blades dip into this tray and splash water everywhere. On a hot and humid day, you can hear a constant “sploosh sploosh”. I drilled a drain hole in a window unit to prevent this.:smack: ---
**Author:** ![TriPolar](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tripolar/32/3008_2.png) [@TriPolar](https://boards.straightdope.com/u/TriPolar)\ **Post date:** [August 16, 2016, 3:45pm UTC](https://boards.straightdope.com/t/air-conditioner-operation-in-the-rain/762986/13 "2016-08-16T15:45:59Z")
> [@lazybratsche](#): > > You make it sound so precisely engineered! On the window AC units I’ve opened up, the condensate drains into a tray under the condensor coils and fan. The fan blades dip into this tray and splash water everywhere. On a hot and humid day, you can hear a constant “sploosh sploosh”. When that happens with my ACs it means the drain hole is clogged. ---
**Author:** ![voltaire](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/voltaire/32/313_2.png) [@voltaire](https://boards.straightdope.com/u/voltaire)\ **Post date:** [August 16, 2016, 4:12pm UTC](https://boards.straightdope.com/t/air-conditioner-operation-in-the-rain/762986/14 "2016-08-16T16:12:26Z")
> [@TriPolar](#): > > When that happens with my ACs it means the drain hole is clogged. Well, such units are designed to retain a centimeter or so of water before reaching the level of the (slightly raised) drain hole. Apparently, some people see/hear the water splooshing, assume the unit isn’t draining properly, and drill their own (non-slightly raised) drain hole, defeating the engineering and decreasing efficiency. ---
**Author:** ![Thudlow\_Boink](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/thudlow_boink/32/320_2.png) [@Thudlow\_Boink](https://boards.straightdope.com/u/Thudlow_Boink)\ **Post date:** [August 16, 2016, 4:25pm UTC](https://boards.straightdope.com/t/air-conditioner-operation-in-the-rain/762986/15 "2016-08-16T16:25:13Z")
> [@BubbaDog](#): > > Running in the rain shouldn’t hurt it at all. As others have pointed out it may actually improve its efficiency. > > I’ve prayed mine with a garden hose on hot dry days just to give it a little boost. Ah, the power of prayer. ---
**Author:** ![TriPolar](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tripolar/32/3008_2.png) [@TriPolar](https://boards.straightdope.com/u/TriPolar)\ **Post date:** [August 16, 2016, 4:36pm UTC](https://boards.straightdope.com/t/air-conditioner-operation-in-the-rain/762986/16 "2016-08-16T16:36:51Z")
> [@voltaire](#): > > Well, such units are designed to retain a centimeter or so of water before reaching the level of the (slightly raised) drain hole. Apparently, some people see/hear the water splooshing, assume the unit isn’t draining properly, and drill their own (non-slightly raised) drain hole, defeating the engineering and decreasing efficiency. Yes, the drain hole is dimpled upward in mine, less than a centimeter though. Never heard the fan splashing unless it was clogged. Maybe just the small amount of water that collects is enough to keep the humidity high in the exterior portion of the units.