this post was submitted on 06 Jul 2025
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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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[–] [email protected] 17 points 9 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.

[–] [email protected] 4 points 7 hours ago

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

[–] [email protected] 9 points 14 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?

[–] [email protected] 7 points 7 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.

[–] [email protected] 4 points 5 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.

[–] [email protected] 1 points 4 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.

[–] [email protected] 1 points 56 minutes 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.

[–] [email protected] 10 points 14 hours ago* (last edited 14 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..

[–] [email protected] 5 points 13 hours ago* (last edited 13 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.

[–] [email protected] 11 points 13 hours ago (2 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?

[–] [email protected] 3 points 12 hours ago* (last edited 12 hours ago) (2 children)

There's no radiator, it's a heat exchanger.

You have two sections in your heat exchanger. One part wants the cooling agent cold so it can effectively imterchange heat from your room into the cooling liquid. The other part wants the cooling agent hotter than the air outside so it can effectively dissipate the heat to the outside. To achieve that the liquid gets compressed. On the cold side it gets cooled with airflow.

I don't think sunlight will change anything significant in that mechanism.

[–] [email protected] 6 points 10 hours ago

I think it’ll have an effect. If you think of the cross section of the piping in the condenser (radiator in the outside unit shown in photo), you have heat trying to transfer from the fluid on the inside diameter, through the pipe wall, then to the air surrounding the outer diameter.

Heat has to flow from hot to cold, so ideally you have a gradient from hot to cold going from inside to outside.

But suppose the sun intensely heats that pipe wall and it ends up higher than either fluid on either side of it. Now you’ve got heat flowing from the wall to both inside and outside.

Not saying that ever happens, but every degree warmer that the pipe wall is, is a slow down in the heat transfer rate. Less of a gradient for the heat flow.

[–] [email protected] 4 points 11 hours ago (1 children)

...I hate the be the one to tell you this but there are two radiators in a heat pump. The condenser and the evaporator are both evaporators.

[–] [email protected] 1 points 11 hours ago* (last edited 11 hours ago) (1 children)

While they both interchange heat, the principle of evaporators and radiators is different.

The condenser and the evaporator are both evaporators

Did you add that to prove yourself wrong?

[–] [email protected] 2 points 9 hours ago (1 children)

probably just a brain fart - they've both heat exchangers.

[–] [email protected] 62 points 1 day ago (3 children)

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

[–] [email protected] 9 points 10 hours ago* (last edited 4 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.

[–] [email protected] 3 points 3 hours ago

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

[–] [email protected] 9 points 15 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.

[–] [email protected] 44 points 1 day ago (1 children)
[–] [email protected] 13 points 22 hours ago

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

[–] [email protected] 2 points 14 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.

[–] [email protected] 35 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

[–] [email protected] 6 points 19 hours ago

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

[–] [email protected] 12 points 22 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.

[–] [email protected] 13 points 15 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.

[–] [email protected] 2 points 14 hours ago
[–] [email protected] 16 points 1 day ago (4 children)

And your HOA just lets you?

[–] [email protected] 6 points 15 hours ago (1 children)

My neighborhood is just too dull to have one I guess. Although once per month the city workers come and pick up leaves and sticks if you place them by the curb, which is pretty exciting.

[–] [email protected] 5 points 10 hours ago

Easy there, chief. Remember where we are right now.

[–] [email protected] 33 points 23 hours ago* (last edited 23 hours ago) (1 children)

It’s a sad reality when people assume having an HOA is a given.

Feel bad for people subjected to it but I’d never purchase a property under the thumb of an HOA. Sucks how ubiquitous they have become.

[–] [email protected] 2 points 10 hours ago

And you can’t legally stop her!

[–] [email protected] 11 points 22 hours ago (2 children)

Not all HOAs are bad... mine pretty much only exists to take care of our neighborhood pool, they've even loosened some of the few restrictions that had been in place since the 70s (restrictions on the type of fencing or sheds has been lifted). And it tends to run with a flat budget so our rates are very low for the area.

[–] [email protected] 4 points 11 hours ago (1 children)

I'm glad it's working out for you, but fuck if I'm about to pay some self appointment group to tell me what kind of fence or shed is unacceptable for me to own on my own property.

If I want to plop down a shopping container on my own front lawn, anyone who doesn't like it can kick rocks.

[–] [email protected] 5 points 10 hours ago

And that's why I'm glad there are properties without an HOA because I don't want to have to see the shit you put on your front lawn.

[–] [email protected] 8 points 15 hours ago (1 children)

For now.

The fun thing about HOA’s is that they can change and are absolutely dynamic. You never know when Karen’s crew is going to come into power.

[–] [email protected] 2 points 10 hours ago

Oh, they also changed the bylaws so that further changes to the bylaws require 75% approval from all homeowners in the neighborhood. Karen's crew is going to have to do a lot of work if they want to make any significant changes.

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[–] [email protected] 9 points 22 hours ago

If you're hot, they're hot!

[–] [email protected] 3 points 17 hours ago
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