Introduction: Solar Powered Air Conditioning Unit.

Picture of Solar Powered Air Conditioning Unit.

Most people would like to have their homes cooled by the strength of sunlight which ironically causes heat. How to achieve energy efficient cooling of your abode by harnessing sunlight?

I have successfully implemented a solar powered air conditioning unit for my living room which has been working great since June 2013 . Let me tell you how I have done it.

Notes to keep in mind:

What I have implemented is an off grid power system. My home generates its own power and can run without utility power. As a result my system is typically much more expensive than one that ties to the grid (feeds power back). I just prefer the option having of power should our utility fail or natural disaster strikes (such as hurricane or a drunk neighbor knocking over a utility line pole with a car).

I have fulfilled the electrical code requirements (NFPA 70, TTS-171 Part 1) and power utility mandates for my area. Grid tie or feeding power back to our utility is both not currently possible and highly illegal in my country (the death of a linesman occured due to a customer violation). This instructable is an overview of how I implemented my system and the cost absorbed by myself. If my implementation cannot meet your electrical code needs, utility mandates, budget constraints and design criteria then I cannot assist you on this. You need to conduct your necessary reseach for a safe design and I'm always happy to try my best in answering technical questions you may have.

I published an instructable on how I solar powered my home with design calculations.

Read on and I hope you can find it interesting.

Step 1: Solar Panels for Harvesting Sunlight.

Picture of Solar Panels for Harvesting Sunlight.

Harvesting? Yes you read it right. Harvesting a renewable resource allows powering of my air conditioning unit and most of my household electrical loads.

An air conditioning unit uses lots of energy to remove heat from a room. To provide that energy you need enough solar panels installed properly to capture the radiant energy of the sun. When it comes to solar power - "the bigger, the better!".

I currently have eight 225watt panels on my roof, wired 4 in series and in parallel with the other string of 4. These give me the energy to power my lights, automation pc, refrigerator, dog feeder, WiFi, small appliances and of course that wonderful air conditioning unit.

Mounting can be with a roof rail kit or you can do your own custom mounts made with metal and/or rigid pvc.

Step 2: Solar Charge Controller.

Picture of Solar Charge Controller.

For 1 kilowatt and higher you want a maximum power point tracking (MPPT) charge controller. Basically it gives higher efficiency, can accept a higher voltage to deliver the amps into the battery bank.

I use the outback flexmax 80amp mppt controller. It's the best in class for the industry and it's worth every cent of its cost. It's fully programmable and can handle up to a 60 volt Dc battery bank.

Notice the happy face I drew? Not even the evil scientist guy in despicable me would be as happy making his evil plans.

Step 3: The Battery Bank.

Picture of The Battery Bank.

My battery of choice is the Lifepo4 chemistry. Long life, zero toxicity, enviromentally friendly, high energy density and best of all completely safe (won't blow up! Lol).

My system is 25.6v and uses 16 batteries in parallel.

I previously used lead acid batteries but they simply didn't last long. In 14 months their capacity was approximately 40% of their original. This was a costly mistake and I gave away these and made my Lifepo4 bank. They have been performing admirably and even though at higher upfront cost, the higher service life is well worth it. Please read my instructable for this bank.

Now for anyone doubting the capabilities of LifePO4 batteries, there are many good sources on the web detailing this chemistry. Also think about this: why dont your mobile devices use lead acid batteries? Hmm. Lithium is superior plus I even have a LifePO4 battery to start my car! Take a look.

Step 4: The Air Conditioning Unit.

Picture of The Air Conditioning Unit.

The only option for solar powered air conditioning is to use an inverter air conditioning unit. This is the most energy efficient type in the industry and it is simply amazing. I actually gave away my original 18000btu unit to install a 10000btu inverter.

My inverter AC unit can use as little as 240Watts right up to its maximum rating. This unit runs off 240 volt so I needed a means to power it.

Step 5: Going From 25.6v Dc to 240v AC!

Picture of Going From 25.6v Dc to 240v AC!

How to make this happen? Easy! I used a 1000watt inverter accepting 25.6v dc and outputting pure sine wave AC at 120v. Next I used a 1500watt autotransformer to boost the 120v to 240v. I included a thermal image of the transformer under load. Autotransformers have higher efficiency at the expense of no galvanic isolation once the voltage ratio is 3:1 or less. I could not obtain a 240volt inverter at a reasonable price at the time of the installation, perhaps in the future I will get rid of that, urgh, transformer.

Protection for my battery bank is provided by a mini circuit breaker 100amp.

Since my pure sine wave inverter can only deliver 1000Watts, the lowest temperature I can get to on battery power is 26C which is pretty good. If you can afford a bigger unit then all the more power to you!

Simple yea?

A side note: isn't it damn confusing reading about a pure sine wave AC inverter and also an inverter air conditioning unit? Don't blame me for that weird terminology.

Also if you don't know if your inverter is pure sine wave here are ways to find out:

1. It would be clearly labeled on its nameplate as pure sine wave output.

2. You can use an oscilloscope.

3. Plug a AC powered fan into the output and if it buzzes while operating then it is NOT a pure sine wave inverter.

4. If the advertised specs claim for example 1000Watt power and a surge rating of 2000Watt, then that inverter may not be pure sine wave. Pure sine wave inverters typically don't have a large surge rating (i.e. 2x its maximum continuous rating).

Step 6: Enjoying Green Energy Air Conditioning!

Picture of Enjoying Green Energy Air Conditioning!

With the inverter on and the air conditioning unit powered, I enjoy comfortable air from my battery bank. I included a thermal image of the unit running off the batteries.

A special note here. This system I have described is part of a larger system for my home. My design was for an off grid system to deliver maximum reliability. The cost for all components is higher than a grid tie system. It has been my aim to introduce some basic design and implementation concepts to others so they may gain ideas for possible installations on their own. It's not the purpose of this instructable to mandate to anyone that this is the ONLY way solar powered air conditioning can be achieved. It's one way and I'm happy to have executed it.

Please note that with my setup I don't have a large enough battery bank to run the unit all night. Therefore I implemented an automatic transfer switch to power the unit from our utility when a low voltage dc threshold is reached.

The transfer switch is fully software controlled by my home automation pc. Take a look at the third and forth pics. The software was created from FLOWSTONE. Take a look at my home automation instructable.


jaylai30 (author)2017-05-21


can you please send to me your diagram for SOLAR AIR CONDITIONING

xakocsianex (author)2017-04-19

how much will it cost to have this assembled?

ManarK2 (author)2017-04-18

After an entire winter of being dormant and not in use, an air conditioning system has a big job at task upon first starting up for the summer. The way an air conditioning condensing unit (outside unit) works is by changing the state of the refrigerant in the system from a liquid to a gas. This generates a heat transfer and cools the air through a coil inside your home. So after 7 months of not being used the component that compresses the refrigerant back to a liquid has not been used and lubricated through the refrigerant.

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ManarK2 (author)ManarK22017-04-18

and thanks for this great post

BigEdB (author)2016-12-13

Greetings !

I've read all your solar instructables, and am really impressed! (I'm a retired (or maybe "tired" electronics engineer living totally off grid). Keep up the good work!

Mr. B

Mjtrinihobby (author)BigEdB2016-12-13

Thank you kindly!

marcelr17 (author)2016-11-26

je n arive pas a le mettre en service

tic solar light duopach mettre notice en francait

PramodD12 (author)2016-10-28

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ssmith204 (author)2016-10-05

You should of used the dc solar power connected to the air con's DC BUS on compressor inverter.

Mjtrinihobby (author)ssmith2042016-10-25


thamesindustries (author)2016-10-24

I am a Nigeria where renewables, especially solar is getting some attention. I stumbled on your very good presentation and can tell you two years down the road " better late than never". Thank you for providing this knowledge sharing forum. It would be a pleasure to partner with you on some interesting solar powered projects here.

KevinB340 (author)2016-07-24

Looking to purchase land and develop a functional modern off grid home. Think I found 15 acres with a cleared area to build. Would you be interested in helping design the solar power system? And if so what steps need to be taken to get a bid from you on cost

Atilla99 (author)2016-07-10

Wow, what a nice setup. First I would like to thank you for sharing your knowledge specially with the Lifepo4 experience, sharing is the key point for mankinds evolution.

I see that you have 4 panels on each side of the roof. How does that effect the efficiency, did you ever consider know how much more you could get with a solar tracker, maybe less panels, maybe not worth the effort and cost? Just curious.

Amitsinha (author)2016-06-30

Is it possible to run ac on battery charged by solar panels

EugineB2 (author)2016-03-17

Hi, this us Gin from Philippines. I just want to ask if what is the voltage capacity of each battery you have? Coz you mention you have a 25v now. We have a single battery and it is a 12v. So to acquire a 24v is I need to have another one? I know this sounds stupid question but we are dealing electricity here and this might not a simple equation like 1+1=2.

nfarrow (author)EugineB22016-06-26

You need to learn about

Ohm's Law

fred3655 (author)2015-04-15

Using a solar panel to run an attic fan is the best return on investment, for anyone paying attention.

Mjtrinihobby (author)fred36552016-06-01


Zamieuth (author)2016-05-19

I work for a large solar and our utility scale panels are 85.6 VOC at around 5 amps I am very intrigued on this idea and would like to talk furthercompany

SopianR (author)2016-04-24

Hi Sir, very nice invention. I just want to know how long the energy will last to support air conditioning? In case I use it during the night, how many hours will it last?


Mjtrinihobby (author)SopianR2016-04-25

just about 4 hours with the temperature set at 28C. If my battery bank were larger then even better. It all boils down to money, how much you are willing to spend on the entire system.

MoG5 (author)2016-04-22

this is really really some beautiful work i would love to figure out all the details possible. I am building a home in morocco and would love to save money on air conditioning by installing such a beautiful system in such a year long sunny country. i hope more people are willing to share similar experiences to help others. thanks

Mjtrinihobby (author)MoG52016-04-22

Thank you very much!

GbengooseW (author)2016-04-18

Hello. You have 8 solar panels running quite a few electronics including the a/c. How many solar panels would you need just to run the A/c unit?

I want to do this for a 350sq ft room. Nothing else will be powered, just the A/c unit.

Thank you!

Mjtrinihobby (author)GbengooseW2016-04-18

Actually since the air conditioner demand is about 80% of the total home load, the same exact number of panels will apply if I only used the Air conditioner. You need to remember factors such as cloud shading and weather conditions will always reduce the energy you harvest. Always max out your charge controller with solar panels to ensure a reliable system. Do not go bare bones on these systems.

cmatkin (author)2016-04-15

In Gin's defense, Why else go to a diy website if not to ask the obvious or not so obvious questions? I'd say your response was rude and a bit arrogant.

GoharA2 (author)2016-04-14

Can you give me your contact number???

KenzL1 (author)2016-03-18

Hi...may i know what is the cost of the solar panel?

STS79 (author)2016-02-03

This is fantastic idea! How many panels would you need if you only ran your AC unit?

marc_cl (author)2016-01-27


first of all I'd like to say this is an amazing project. I have a question though that you might be able to answer for me. is it possible to transform a "conventional air conditioner unit" to function as an inverter one?

Mjtrinihobby (author)marc_cl2016-01-27

This is a question I personally pondered before replacing my standard air conditioning unit. Theoretically you can power the compressor motor with a variable frequency drive. The problem is the compressor motor is not rated for use on such drives since it will experience insulation failure due to the fact vfd output is not perfectly sinusoidal.

To sum up, even if you tried it, it would actually be cheaper to install the inverter type rather than heavy mod a standard unit. Also the safety factor of potential fire hazard makes modding very unappealing.

Kinnishian (author)2015-12-29

I appreciate the intent and effort in this. You also documented a lot of your general solar build (in that sense, an excellent solar power instructable.)

But I have some misgivings about the title and effect. It's really...."standard powered air conditioning unit" where the standard power you develop is interesting and impressive, because you make it from solar. But I didn't see anything really specific about the solar power air conditioning unit, besides that it is single-phase (lots of split units are three phase AC)

Mjtrinihobby (author)Kinnishian2016-01-19

Thanks for the compliments. Solar powered devices derive power from photovoltaic equipment but they are often standard design equipment that can take power from utility or inverter. Special note goes to dc compressor air conditioning equipment that is very easily tailored to solar power.

CraftAndu (author)2016-01-19

This is so clever!

Mjtrinihobby (author)CraftAndu2016-01-19

thank you kindly.

dragonkx (author)2015-04-16

With 8 solar panels on the roof, your pretty much setup for a full solar system (depending on house size). I prefer sunpower panels, their more efficient and can produce 300+ watts per panel. All you would need is an inverter, and 2 20 volt breakers and tie it into your breaker box. It would power the whole house, or reduce the cost and feed back into the grid for unused power. It would avoid the battery pack.

Mjtrinihobby (author)dragonkx2016-01-18

again, grid tie is not possible in my country.

ary3 (author)2016-01-04

Hey a fellow Trini! Love the instructable. Been looking at solar panels for a little while but the cost of shipping them home is a killer. I have a small set up in the car though, a 60Watt panel and 300Whr LiPO4 battery bank, both from AspectSolar. Where do you order your panels from? I see some online for reasonable prices but I'm scared of the cost.

Mjtrinihobby (author)ary32016-01-05

ah! I bought them from ECT Solutions in Cunupia (679-3444). The owner's name is Haroon is I remember correctly. He delivered right to my home. To me they are the best on the island. 225Watt panels in 2013 were 3500TT, prices have since improved significantly. I'm interested in that you have a LIFEPO4 battery. My car also has it for starting the engine.

Private message me for more information or questions!

ary3 (author)Mjtrinihobby2016-01-18

Sorry, I've been busy last couple of weeks. I think I met him, that place is just 10 minutes away from where I live, never checked them out before (lol). The LIFEPO battery doesn't replace my car battery, I just have it for portable power mainly, and to power some auxiliary equipment. Very nice for not draining the car's battery. I will check out ECT solutions, looking to build a small set up to power some outdoor LED lights, and maybe a security camera system.

Left-field Designs (author)2016-01-17

Great description of the power system. Have you considered super capacitors or ultra capacitors to replace the batteries. Even ups batteries like the ones you use have a limit of a couple of thousand charge cycles, also batteries are only about 60% efficient. Capacitors however are close to 100% efficient, have hundreds of thousands of charge cycles and also have no internal resistance so are more efficient to charge. The will however cost more money in the first place.

Here you went wrong:

1. My batteries are NOT ups batteries.

2. The charge efficiency % of my LIFEPO4 batteries are in the early 90s.

3. Capacitors are NOT 100% efficient.

4. All capacitors have unacceptable high self discharge rates. This is why you don't find them powering cell phones, laptops, mobile power etc.

5. Which solar charge controller on this planet will deliver charge to your proposed capacitor bank? NONE!

6. How do you plan to balance the charge across series sets of capacitors? There are no systems available commercially to do that.

7. All capacitors have an internal resistance which is prohibitive for high current electrical loads.

NikhilJ5 (author)2015-05-16

And how do you feed your 1000w inverter and 1500w autotransformer. I think they themselves are taking 2500w/hr. While your ac on a standard load must take only about 1400w.

hippiechk (author)NikhilJ52015-12-29

i didn't write this but can answer your question. Inverters/transformers only draw up to the rated amount when they feed to a device. The inverter itself draws a very tiny amount when not in use and only if if it has an Indicator light. In use the inverter/transformer will also run a small cooling fan but again, still draws only a very small amount.

I hope this helps, its been a while. Keep trying the math back & forth can take a bit to grasp. Happy New Year!

bratan (author)hippiechk2016-01-18

You are not entirely correct. In inverters draw more power in standby than what is needed to power indicator led or a fan. I have same brand of inverter as author, and it can noticeably deplete beefy 12V AGM battery I have in my shed overnight. Without any load! Fortunately it has remote control circuitry which allows me to put it in "deep sleep" mode where it really draws less power than LED.

Gilius (author)2016-01-17

So you're converting DC to AC so that the air condtioner can take that AC and pass it to an inverter to make it into DC. Wouldn't it be easier to tap into the inverter of your air conditioner somehow?

Mjtrinihobby (author)Gilius2016-01-18


Kinnishian (author)2016-01-14

I think in fact the retrofitting of a standard AC based air conditioning system to the rarer DC powered scroll compressors, might be a better definition of "solar powered air conditioning unit." But upon further thinking, I'm a little misguiding in thinking that. By and large, it's probable that any "DC scroll compressor" (like in those 12V/24V REAL compressor fridges) is in fact a BLDC variant that is not that different than the AC motors. So by using a sine wave converter on your AC...I guess you are kind of using a DC system, I mean, it's not much different that's all (the biggest difference is you're stepping up your voltages as opposed to using a compressor wired for more current and less voltage.)

In fact however there is one more way you can get solar powered AC, but I wouldn't expect anyone to have tried it. Look up "vapor absorption cycle" it's what the propane fridges use. It would be very cool if someone made one, but would mostly only benefit if you live somewhere always with enough sunshine to need to use it (because you can't get anything except cooling out of it, unlike a solar panel where you can also charge your devices if you don't need the solar during the winter.)

WilfriedS3 (author)2016-01-13

If I have it right your system provides enough energy for your entire home which includes a single AC unit.

If i want to AC e.g. 5 rooms, for some of your set up i simply require bigger meaning more powerful equipment, that is obvious.

But I doubt i need 5 times the battery bank (which would be 60 batteries) and was wondering if there is an easy calculation that can be made. I am afraid I do not know much about batteries, am just assuming you are already using the biggest ones commonly available.

Mjtrinihobby (author)WilfriedS32016-01-14

trust will need an enormous battery bank. Think of it this live in the forest and depend solely on rainfall for water..would you really insist on having a small collection tank or get the biggest tank you can afford? think about this carefully.

About This Instructable




Bio: As of April 2017 I have decided to no longer post on instructables. The fact that several of my published works have been removed without ... More »
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