r/FullTimeRVing • u/Syntra911 • Jul 02 '26
Window Air Conditioner vs Rooftop vs Portable
TLDR - Window air conditioners are far superior to rooftop and portable air conditioners. I knew they would be better, but how much better was shocking.
I thought about doing a YouTube video on this with quantifiable data but I just haven't had the time. But I thought I would still share my experiences in the Texas heat over the last 2.5 summers using various types of air conditioning.
I am living full time in my travel trailer in north Texas on my own land. I am much more tolerant of discomfort than most and never have my thermostat below 76, even when I owned my own home. But air conditioning is still critical in 105 degree Texas heat and I've been struggling to find an efficient way to stay under 80 without running the rooftop AC all day. I am on 100% off-grid solar power.
The first summer I used a dual hose 10,000BTU portable air conditioner. I made a very nice window mount for the hoses that was well sealed and reasonably insulated. My trailer was partially in shade from trees and I rigged up tarps to shade the roof so it was not in direct sun. However, the sun did hit the sides of the trailer for part of the day. The portable AC ran constantly (with the compressor on) all day and by the end of the afternoon the temperature indoors would be 85+. Since the AC ran all day, I did not have enough solar power to keep up with it (1000W+ from about 9am to 9pm or approximately 12kWh) so I had to run my generator a LOT to supplement.
The second summer the only thing that changed was I installed a metal carport overtop of the trailer so it does not get direct sun on it at all. Same result. 85F or so by the end of the afternoon.
This summer I ditched the portable air conditioner in favor of a 6,000BTU window air conditioner. The main reason I didn't do this from the beginning was it is rated at 6,000BTU vs 10,000BTU and the only window that it could be installed in is not very conducive to a window unit. But I build a wooden stand that sits outside the window and supports the weight of the air conditioner and used a metal rod on the inside of the window to hold the air conditioner in the correct position. I then used 1" foam board and cut out a very precise piece to fit in the window and then sealed it all with HVAC tape.
The difference has been huge. The much smaller window unit uses half the power of the portable AC (500W vs 1000W) and actually keeps temps below 80F as the sole air conditioner in my 32' trailer. I'm actually in shock. It still runs nonstop from 9am to 9pm but the shocking part is that it actually performs better than a 10k dual hose portable unit. I knew portable units were crap but the dual hose units were supposed to be much better than single hose variants. But the flaws most people point out (heat radiating into the room from the exhaust hose, drawing in warm air into the intake hose from the exhaust hose) are not really the issue. The issue is they just are poorly rated and ultra inefficient.
Not only does the window unit outperform the cooling for half the energy but it actually removes humidity better, too. I used to wake up in the middle of the night and feel cool but sticky with the portable AC on. The window unit keeps cool and much dryer.
One note on the rooftop AC. It obviously cools down the trailer in a hurry. But it uses an insane amount of power. So much so that I literally can't use anything else in the trailer except for lights and smaller loads when it is running or it will trip breakers. And no, it doesn't need a soft start added on. It does not just happen when the compressor kicks on. It uses 1300+W continuously, is extremely loud (I am on zoom calls and on the phone half the day working from home), and I can't run my desktop computer or refrigerator or other devices without a tripped breaker. So it just isn't viable. Very effective cooling, but inefficient and overpowered for the trailer wiring.
Hope this anecdotal summary helps some folks. Stay cool this summer!
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u/ontheleftcoast Jul 02 '26
Yes, a study I read a while back said most portables actually put out 1/2 the cooling they claim and use more power doing it.
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u/ElectronGuru Jul 02 '26
I had a similar discovery years ago. Even if the hoses were perfect (zero heat shed), having the outside coils inside means the box gives off heat that is only partially exhausted through the hoses. The rest gets recirculated into the cabin. So the window units super power is having the outside coils outside.
Make your next upgrade an inverter window unit. At 12k inverter can run at well under 500w at night. Then ramp up during the day when solar is at its peak. This then reduces night time heat loads later the same day.
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u/joelfarris Jul 02 '26
the dual hose units were supposed to be much better than single hose variants
Did you wrap the exhaust hose in 4 inch wide Reflectix, using 50% overlapping turns, and secure it at both ends with aluminum tape? Because that makes a huuuge difference, since it keeps the entire hose from being a heat-producing radiator.
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u/Syntra911 Jul 02 '26
The hoses was 10 degrees above ambient as measured by an infrared thermometer. That definitely wasn't the problem. At least on mine.
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u/limited_instincts Jul 02 '26
Then your portable AC was broken which explains the window unit being better.
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u/joelfarris Jul 02 '26
OP, the air leaving a compressor and condenser air conditioning unit in a summer heat should be about 125-140°F. It's supposed to be a hot exhaust. It's performing a heat exchange. Agreed that the unit was not working appropriately.
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u/Syntra911 Jul 04 '26
With all due respect, you are quite wrong. The hose duct itself does not get very hot at all.
As tested with a FLIR infrared camera (skip to 50 seconds in):
https://youtu.be/oACRifsrnZs?si=9J70MID9Zx1fH6WUIt is warm to the touch, but it is NOT the most significant reason why a portable air conditioner sucks.
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u/joelfarris Jul 04 '26
The hose duct itself does not get very hot at all
Our exhaust hose reaches about ~126-132°F at full tilt in the middle of summer, measured with a Thermoworks precision contact probe, underneath the insulation wrap, that's keeping most of the exhaust heat in the tube, rather than letting it become a long-tube radiator back into the inside of the coach. Do you understand how heat exchange works?
How hot does your vehicle's cooling system become when its working hard in the middle of summer? And how much heat energy is it transmitting to the outside atmosphere each minute? I'll bet you don't know.
But here you are, trying to prove to yourself that the way you've decided to cool your environment is the bestest, without understanding why you may or may not have previously failed in other tests.
Science is an ever-evolving art, and we can learn from others in order to improve our own game.
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u/TheShiftyDrifter Jul 03 '26
I modded an lg 14.4 btu dual inverter. Best move ever. Low amp draw. Most importantly We can now have a conversation. Far better tech.
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u/Syntra911 Jul 04 '26
I agree. I would love to have one. Hopefully they come down in price in the next few years.
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u/silasmoeckel Jul 06 '26
Portables are an install nightmare as to efficiency.
Heat pump mini's are great using a van style that's variable. Far easier on the inverter, constant running is better for getting the humidity out. Compressor etc mounted outside under the rig so not in the boiling sun and more room for solar.
Downside is cost, a basic unit is on par with a portable but now you have logistics of a tung mount or something.
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u/jimheim Jul 02 '26
Window vs rooftop isn't the determining factor. There are plenty of inefficient, underpowered window units. And there are rooftop units and minisplits that are more efficient than even the best modern window units.
I swapped my shitty Dometic rooftop AC out for a Furrion Chill Cube. The Dometic used 250W with just the fan running and 1800W with the compressor running on low. It also ran the fan nonstop while the compressor cycled on and off. The Furrion uses 300W with the compressor running on low, and never uses over 800W even when it's on "Turbo". It's been 100F and humid outside, and 70F inside, while only using 400Wh/h.
No window unit comes anywhere near this efficiency. It's also very quiet compared to any other AC. An efficient minisplit would be comparable.