minimal requirements for window a/c unit, post-hurricane

Greetings, photosynthesizers.

I am very interested in energy efficiency, but have no practical experience with solar panels and batteries. I live in a hurricane-prone area and was wondering about the feasibility of running a small window a/c unit post-hurricane with solar, when grid power is down. In general, I can camp in my own house with no power comfortably for a few days, with the exception of being unable to sleep when that post-storm heat, stillness, and humidity settles in.

Running a gas generator at night is a good way to make your neighbors hate you, and also get your generator stolen/damaged.

My question is, what would be the minimum necessary investment to keep a small room at a reasonable temperature and humidity-level with a window a/c unit and maybe the ability to charge a phone?

The a/c unit I was looking at was this: Frigidaire GHWQ083WC1

This claims to be as efficient as the U-shaped one you guys suggest, but seems easier to install. Note that this would not be a permanent installation in the window, just something I'd use in case of emergency.

Also, given that this would not be a full-time set-up (I don't actually have space for the panels full-time, but could certainly deal with them in this case), I am not so interested in picking up rolling my own generator package as a hobby. I am quite willing to take the boring way out and get an out-of-the-box solution. I was looking at the EcoFlow units, but I don't know if running the a/c unit on one of the smaller models is a complete fantasy or not.

I'm basically just trying to figure a ballpark cost and equipment solution. If the cost creeps up high enough, it probably makes more sense just to pack up and drive as far away as necessary to get a hotel until the situation calms down.

I'm open to any suggestions, including opinions as to why the a/c unit I'm looking at might not be the right one for the problem, and I'm not married to any particular brand of battery/panels.

Just working through this as a mental exercise makes me realize how crazy it is that humans even settled this part of the country without immediate access to electricity!

Thanks for your time.

Some comments in no particular order.

You picked an inverter AC unit which is the best option in regards to energy efficiency and startup load demands


I have a 12k Midea U inverter AC. At full power, I think it takes about 1kw. Full power occurs when settings are on high and the difference between the set temp and indoor temp is large (don’t know the threshold but think it begins around 6 F).

Now some very simple math. Location is important but you can adjust the numbers. 24 hours x 1 kw x 50% utilization = 12 kWh per day.


The 1 kw power draw determines the inverter size. In this case, I would get a 3kw inverter that is a common “size”.


The 12 kWh relates to your battery bank. Using worst case scenario, you can say I want 3 days of AC when the region looses all power. 3 x 12 x 1.20 factor to compensate for efficiency x 1.2 for battery reserve = 52 kWh.

Now, since you have a generator, you may say I just want 1.5 days so that is 26 kWh.


The 12 kWh also impacts the size of your sole array. You want to be able to collect enough solar. Again simple math here with no info on your location. 12 x 1.5 factor to compensate for location / 4 average daily Solar hours = 4.5 kw of Solar. I repeat my self, these numbers can swing drastically based on the above numbers and location.



Cost wise
3kw inverter is $800 to $2000

26 kwh battery is $5,200 (computed at $200/kwh)

4.5kw is solar panels is $1,100 - 2,250 (computed at 0.25 - 0.50/watt)

Subtotal is $7,100 - $9,500

Add 20% misc items such as wiring, mounting hardware, tools, etc

DIY price is $8,500 - $11,400

For informational purposes, Hire it done price is 3-4x so let’s use 3.5x
$30k - 40k

I repeat my self again, estimates above will vary greatly based in assumptions and location.

If I were looking for a temporary AC for emergency use, I would look at an RV Air conditioner that runs off DC.

Panels, solar charge controller, battery. Skip the inverter.

Make a portable battery backup/inverter system and use an inverter AC. Get a small quiet portable generator for recharging the batteries for a few hours a day.

You can take the 30% tax credit on any battery system greater than 3kWH.

Adding a second battery to this example would get your AC to last over night.

Is it really realistic that you going to be sitting there in the dark with the air-conditioner running? Also, what's the weather going to be like just one day after the hurricane passes over?

I think it's a far better option to plan for keeping the frig running, powering some lights, and TV, with some left over for air-conditioning. At my own cabin, I've installed a wall-mount air conditioner, with the idea of running at full speed during the day, and on into early nightfall, and then shutting it off sometime around midnight when outside temperatures have dropped below the air-con set temperature.

I could suggest that you are likely to get by with a significantly smaller investment if you focus instead on keeping the frig and lights on, with extra to keep the bedroom cool.

I think a 48V system with at least golf-cart batteries will give you enough power to get through the night, if you carefully manage the air-conditioner? There are some good strategies for saving some money here.

First, do NOT buy solar panels online. Go to Craigslist, or FaceBook Marketplace and shop for large high-voltage residential panels online, but with cash and carry purchasing. I'm seeing 30V, 250W residential panels going for 50$ recently. That's only 200$ per thousand watts of solar.

Based on what I am seeing for my own system, I'll suggest you need to generate ~10kWh of power per day, with maybe half of that drained from the battery at night-time. If you use rotating mounts like I have, you could mount 1000-1500W of panels on a single rotating array.

Run the air-con at full-blast during the day, and coast with it cycling on and off after sunset. I think you could get by with 1500W, but 3000W would be better. If it's cloudy the day after the hurricane, but the power is off, I'd think that keeping the frig on is a higher priority then keeping the room cool. Even in cloudy weather, at least 3000W might make enough power to keep the batteries close to full charge if only the frig is running. So, call that 600$ for 3000W of panels.

If you can really cool down the room during the day, and switch over to battery at night, you can get by with maybe 5kWh overnight. CostCo sells a 6V 220Ah golf-cart battery that's running 110$ right now. Eight of those for 900$. You don't want to deplete lead-acid to less than 50% capacity, so (220Ah X 50% X 48Vbattery bank) = 5280Wh, or ~ 5.3kWh of battery power. With an air-con cycling on and off at night, I'd suggest you'll be running at ~350W/hour, so that should get you through the night.

You'll need a good MPPT charge controller to handle the 60A that 3000W of panels are likely to make. I myself went with the Midnight200, but a more economical brand might be the Epever Tracer 8420AN. The 8420 has a 200V limit, which will allow you to wire those panels 3S or 4S, depending on what you buy.

Now, the inverter. You want a quality sine-wave inverter for anything that runs on an electric motor, which means refrigerators, freezers, air-conditioners, and fans. I myself have Schneider's Conext 4024, which is an excellent inverter, but they also make the 48V model, the 4048. Besides just being sine-wave, it also offers split-phase 120-240V, and an automatic generator charging circuit, so generator power can be seemlessly be fed into the inverter to charge the batteries if the clouds really won't cooperate. That inverter will run you ~1600$.

Lastly, a transfer switch, copper wire and fuses/breakers to connect it all. You want a transfer switch between the solar system and your main electrical panel, so the solar power can NEVER mingle with grid-power. Do NOT exclude the transfer switch. Lives may depend on it. Use fuses or breakers for each solar string (more than two strings). Use 10 gauge copper wire from the panels to the charge controller, 6-4 gauge wire from the controller to the batteries, and HEAVY 00 or 000 gauge wire from the batteries to the inverter. Use the same gauge of wire between batteries as what goes to the inverter.

So, lets add up the numbers....
Twelve 250W panels: 600$
Eight 6V batteries: 900$
MPPT Charge controller: 350$
Sine-wave inverter: 1600$
Wire, fuses, spit, ect: 250$
Total: 3700$ A bit more with taxes, shipping, and any core-charges, but let's say <4000$ out the door.

Thanks, you guys have given me a lot to process and a lot of numbers to check against specs. It's now clear that I can't get away with a $500 self-contained unit with the associated small panels.

I watched the video Browse linked to and even though the construction looks pretty simple, I don't feel confident in my ability to do so. For example, he said "obviously you don't plug this in while the panels are connected" and I didn't understand the danger, so I don't even have a baseline reasonable competence. Since I don't plan to make this a real hobby and am really only interested in using the system in case of emergency, hopefully no more than every few years, I don't really have the experimental drive to manage the project safely.

I would feel comfortable using hardware you guys would dismiss as overpriced garbage for the uneducated masses, but that kind of idiot-proofing looks mighty expensive.

To answer some of the hurricane-specific questions Michael asked, I've found the night to be when I want a/c the most during an outage. Post-storm, the humidity is typically incredibly thick and the temperature does not drop significantly, making sleeping nigh impossible. The daytime is usually occupied with cleaning up the damage outside, which is also awful, but you can't work with an a/c strapped to your back anyway.

I have gotten good at emptying the fridge as the storm approaches. It's no contest between a/c and a fridge for me. A fridge just heats up the interior of the house and doesn't help you sleep. Being unable to sleep is the thing that drives me from my home.

Also I should note that I don't have anything like the space available for panels as in Michael's photos. I have limited roof space that I could really only use temporarily.

Thanks for again for all your considerate help. It has given me a lot to think about.

You could probably get by with any of the larger portable power stations...Ecoflow, Bluetti, Anker, etc. with an additional battery or two. Lots of reviews on Youtube for those. Add a small inverter generator or some solar panels for recharging and you should be fine for shorter outages. Gavins Garage on Youtube has a lot of reviews for various models you can peruse.

The fridge isn't going to use that much power compared to A/C.

The idea is to run the A/C during the day to get the humidity in the house down. That minimizes the batteries which are the expensive part. So run it wide open during the day to dry out and cold soak the house and then basically let it coast overnight with minimal batteries.

It will probably be cheaper to get a Pulsar 2200W Propane generator and a 100LB propane tank. That'll power a window A/C for idk, maybe 3-4 days. Get 2 tanks for longer runtime.

Otherwise, you need like an EG4 3k, 5kWh battery, and 4 big solar panels (400W+) at a minimum. Not to mention even with an adequate setup, if the weather is cloudy and rainy after that hurricane you're still going to fall short.

Thanks for the lesson on cooling, teal95, that's an important way of looking at the issue of humidity that I wasn't considering.

And thanks to Browse and hwy17 for more data to process. I will check out those videos and take a closer look at what panels are offered in the bundles I was looking at. I'm thinking those panels might be the limiting factor that makes the whole plan unmanageable.

But that's what I wanted to find out by talking to you guys.

Interesting that the thing that makes life feasible down here is also the most energy-intensive. Ain't no free lunch.

I'm still working on training my wife on living with the solar system. She wants to leave the A/C off until about 4 pm and by that time the solar output is already decreasing rapidly so it kills the batteries. Add cloud cover and the batteries haven't been fully charged in a week. But last months electric bill was $13 instead of $500.