this post was submitted on 06 Jul 2025
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Every year I install this sunsail to shade my ac unit. (dullsters.net)
submitted 1 day ago by admin@dullsters.net to c/Dullsters@dullsters.net
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Shading the condenser unit keeps it cooler and increases it's efficiency and helps keeps my electricity costs down. The sail is high enough and mesh like so that it doesn't trap the hot air. In fact it creates a slight wind tunnel effect. The shade it provides lasts during the hottest part of the day and a tree helpfully blocks the sun for the remainder. The unit is never in full sun this way. Keeping the weeds and other debris away from the unit so that it gets good airflow and cleaning the condenser every year also help with the units efficiency.

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[–] wetbeardhairs@lemmy.dbzer0.com 18 points 11 hours ago

You're blocking 300-500 W of solar radiation on a heat exchanger that runs 20-100% of the day. So yeah you're definitely going to get some improvements. Most notably it will run less often because it isn't dealing with the excess heat.

AC units SHOULD be designed for 100% duty cycle. But we all know that nothing is really capable of that - even industrial stuff. So if your shade reduces the duty cycle by a few percent, you might increase the longevity of the unit by an order of magnitude.

[–] GaMEChld@lemmy.world 4 points 8 hours ago

Interesting. I should see how much sun my units get.

[–] Machinist@lemmy.world 10 points 16 hours ago (2 children)

This is interesting. Gut says that it does increase efficiency. Thing I'm questioning is by how much?

Anybody got numbers or a good educated guesstimate?

[–] nednobbins@lemmy.zip 8 points 8 hours ago (1 children)

https://www.aceee.org/files/proceedings/2002/data/papers/SS02_Panel1_Paper24.pdf

Shading the compressor can help but it can also hurt.

Those units can draw enormous amounts of air. Unless the shading covers a very wide area around the compressor, it's likely to mostly pull in air that wasn't shaded and is still at normal ambient temperature.

If the shading obstructs airflow, it can reduce the efficiency of the unit.

[–] Machinist@lemmy.world 5 points 7 hours ago (1 children)

Nice source! Thank you kindly.

Planting trees and shrubs close by a condenser may actually reduce system efficiency due to impedance of effective air movement. We conclude that any savings produced by localized AC condenser shading are quite modest (<3%) and that the risk of interrupting airflow to the condenser may outweigh shading considerations. The preferred strategy may be a long-term one: locating AC condensers in an unobstructed location on the shaded north side of buildings and depending on extensive site and neighborhood-level landscaping to lower localized air temperatures.

Tracks with the gut feeling. Shade will only marginally improve efficiency but constricting flow definitely hurts. Units are best installed on the North/Northeast sides of houses in the northern hemisphere.

[–] sevan@lemmy.ca 2 points 6 hours ago (1 children)

If your unit is a heat pump, are you then paying for that savings in the winter when it doesn't benefit from any solar warmth to help heat your house? If so, I wonder if it is a relatively balanced outcome or if one of the seasons has a bigger impact. I imagine it depends in part on which season is more extreme in your area.

[–] Machinist@lemmy.world 1 points 2 hours ago

I would think so. Another factor would be dropping leaves in the fall and winter so less shade, a good thing, in this case.

[–] Madzielle@lemmy.dbzer0.com 12 points 15 hours ago* (last edited 15 hours ago)

Not going to give an educated guesstimate, but I do know our ac unit is in full shade of trees, with not much greenery around. It is probably 20 years old. We were told, ten years ago by a repair man, it was close to kicking the bucket, yet it's still going.

My neighbor, has the same unit, newer, leas than ten years old unit, in full sun with bittersweet growing all around it. Last summer they spent half the time trying to fix it, and this year I saw them install window units..

I'm guess, it helps to have it shadded with no plant debris. Purely anecdotal.

Knock on wood oh boy..

[–] vxx@lemmy.world 5 points 15 hours ago* (last edited 15 hours ago) (1 children)

I doubt it will make it more efficient. The air it sucks in is still the same temperature.

It might help with longevity of the device itself though, as it doesn’t stand in direct sunlight.

[–] wetsoggybread@lemmy.world 14 points 14 hours ago (8 children)

By keeping the sun off it, that helps with keeping the equipment cool which the radiator is part of so there's less heat the fins have to dissipate no?

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[–] dohpaz42@lemmy.world 65 points 1 day ago (3 children)

Have you been able to quantify how much more efficient your unit is because of the shade?

[–] Itsamelemmy@lemmy.zip 9 points 11 hours ago* (last edited 5 hours ago) (2 children)

I have an emporia energy meter. While I can't answer your question exactly, I have sprayed mine with a hose during the hottest part of the day and watched the power usage drop a decent amount. So I imagine as long as the shade wasn't too expensive it'll pay for itself.

Sprayed it down with the hose again. Pic added showing energy usage drop. Doesn't last long from water, but does show it not working as hard when cooler.

[–] dohpaz42@lemmy.world 3 points 5 hours ago

Thank you for that visual! And for the new item to research for my home (the meter). 😁

[–] admin@dullsters.net 9 points 16 hours ago

Sadly there are just too many variables in play. Many other changes have been made to help keep costs down such as different thermostat settings, extra insulation, and duct sealing. It does all add up to quite a bit of savings.

[–] baguettefish@discuss.tchncs.de 42 points 1 day ago (1 children)

I reckon at least three

[–] Tylerdurdon@lemmy.world 14 points 23 hours ago

Boy I'll tell you what, 3 is alot.

[–] Semi_Hemi_Demigod@lemmy.world 36 points 1 day ago

I have mine under some trees. It’s shaded in the summer and in the sun in the winter, which helps because it’s also a heat pump

[–] CrazyLikeGollum@lemmy.world 12 points 23 hours ago (2 children)

I'm curious why you rehang it every year and don't just install a retractable awning. Hell, putting some smaller retractable shades over the windows, especially the sunnier ones, would probably also save you a chunk of change on those bills.

[–] admin@dullsters.net 14 points 16 hours ago

Snow weighs quite a lot! So it must come down after a/c season is over. This was $20 4-5 years ago. I wish retractable shades were in the budget, that would be awesome.

[–] cdf12345@lemmy.zip 2 points 15 hours ago

Makes me think of this gem

https://youtu.be/FBaMfUiTq-E

[–] Macaroni_ninja@lemmy.world 6 points 20 hours ago

Same goes for heat pumps, a little shade can prolong their life and increase effectiveness.

[–] friend_of_satan@lemmy.world 2 points 16 hours ago

Shit, my AC unit is on the south side of my house. Should've built the house with the furnace on the north side.

[–] ramenshaman@lemmy.world 4 points 18 hours ago

[–] dumbass@quokk.au 9 points 23 hours ago

If you're hot, they're hot!

[–] xia@lemmy.sdf.org 18 points 1 day ago (4 children)

IIRC, my AC guy said the vertical throw of those units is far higher than that, I wonder if that translates into it sucking in more of it's own air (less efficient, higher cost)? Then again, UV seems to destroy everthing...

[–] admin@dullsters.net 6 points 6 hours ago

This is what I came up with. I'm not seeing any heating of the siding it's hard to tell on the sail as it's in direct sun. Also the unit is just under the corner of the sail so air can definitely get up and around. There's about F10* difference between the siding in direct sun and the condenser.

[–] ceenote@lemmy.world 14 points 1 day ago* (last edited 1 day ago)

I doubt it. That's quite far and it's open so there's plenty of room for it to spread out. You wouldn't want part of your building to be in the air stream because the air from the condensing unit would heat it up, but it's fine if the tarp gets warm.

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