- What Is a Mini Split HVAC System?
- Our Picks for Best Mini Split Air Conditioners
- Best Mini Split Comparison Chart
- Can You Install a Mini Split System Yourself?
- How Hard is it To Install a Mini Split System?
- How Long Do Mini Split Air Conditioners Last?
- How Much Does It Cost to Install a Mini Split Air Conditioner?
- Do You Need a Mini Split in Every Room?
- Does a Mini Split Heat in the Winter?
- What is The Best Mini Split Brand Name?
Mini Split air conditioning systems are one of the best ways to heat and cool a home.
They cost much less compared to traditional home HVAC systems and cost much less to operate in electrical cost.
This post is here to help you find the best mini split that fits your heating and cooling needs.
What Is a Mini Split HVAC System?
A mini split is a small HVAC system that has separate inside and outside evaporator condensing units.
Two small copper refrigeration lines are run between the two units transferring heat away or into a home.
This allows for the units’ loud, noisy components to be placed outside and quiet parts placed inside.
It also makes them very efficient and low-cost to operate with high SEER ratings.
Mini split units cost much less compared to standard HVAC units.
They are very popular since there are many Do-It-Yourself kits that can be installed by a homeowner bringing down cost.
Mini splits do have their limitations since they don’t push air through ducts; they really only cool and heat the room they are in and don’t push on past walls.
This makes them ideal for garages, home add-ons, mobile homes, or any area that needs a low-cost, long-term solution to heating and cooling.
Homeowners can take advantage of a mini splits cheap cost to operate while cooling one section of a home when the rest isn’t used much.
I am one of those homeowners that love mini split cooling systems and have three installed at strategic locations in a three-bedroom home.
Even though there is a traditional HVAC unit in my home, it is much cheaper to cool the room I am in at the time instead of the entire house.
Plus, mini split units have very high SEER efficiency ratings, which can drastically reduce a power bill.
What works for me will not work for everyone, so it is simply an example of how versatile a mini split is and how it can be used to your advantage to save money long term.
There are many units available in all sizes and price ranges, below are simply the best options I have found and my own personal opinion.
After installing many mini split units, below are the best DIY kits I have set up and have been using.
I also wrote post and made videos of installing the units to show the steps involved.
Be sure to read the reviews on Amazon, forums, here or elsewhere to be sure a unit is a good fit for you.
*This site contains affiliate paid links for which a commission earned.
Our Picks for Best Mini Split Air Conditioners
- Pioneer
- Senville
- MRCOOL DIY Series
- Daikin
- Mitsubishi Hyper Heat
Pioneer makes several units from 9000 BTU to 36000 BTU along with both 120 volt and 220 volt systems.
They have become very popular since they send a whole kit that is perfect for Home DIYers.
A pad to set the unit on and electrical to the pole is not included and will need to be bought separately.
Installing a unit is not hard but does require some skill so be sure to call a professional if needed.
I installed a 12000 BTU unit and it has been working very well. It was installed for a friend in a home addition that had no A/C and made a video along with a post of how I install a Pioneer mini split here.
Most standard home units are measured in Ton instead of BTU with a 12000 BTU unit equal roughly to a 1 Ton unit.
For example, a 1-Ton air conditioner is rated at 12,000 BTU per hour. A 2-Ton unit would be rated at 24,000 BTU per hour.
Most homes usually have a 2-5 Ton unit on the roof, depending on how many square feet the house is.
So far, this unit has worked very well for me, along with the ability to install it without the need for an HVAC company.
Read Here For How I Installed the Unit
Senville is another popular brand that has an entire mini split kit that comes with everything needed to install the system, except for electrical wiring.
It comes in different sizes 9000 BTU, 12,000 BTU, 18,000 BTU, and 24,000 BTU.
I installed a 9000 BTU unit and made a video along with a post showing how I install a Senville unit which is here.
Mini splits come pre-charged with refrigerant that is released after the line set is vacuumed out.
Even though someone could be hired to install it this is also perfect for the home Do-it-Yourselfer (DIY).
Tools will be needed if you do it yourself, such as a vacuum pump and HVAC gauges, but these can be picked up cheap compared to the cost of hiring an HVAC tech.
A handy person combined with all the YouTube videos out there most likely can install a mini split in a day or two.
Read Here For How I Installed a Senville Unit
Of course, someone can be hired to install the system, and this may be the best option for many people.
If you do decide to install a mini split yourself, the most difficult thing will possibly be the wiring.
The electrical is not difficult if you have done it before, such as wiring a dryer or ceiling fan.
Of course, the electrical can simply be outsourced to an electrician who will wire it in quickly if needed.
The MRCOOL DIY Series of Heat pump mini split units are marketed for DIY individuals.
Everything comes with the kit except the electrical, including the line-set and pre-charged unit.
The MRCOOL mini split units do cost more compared to Pioneer or Senville but are very popular and used by many.
One of the things that makes MRCOOL units different from other mini split kits is there is no need to vacuum down the lines.
MRCOOL line-sets are already in a vacuum and have a seal that is broken when bolted onto the outside condenser.
This makes them the easiest to install, with no need to worry about vacuum pumps and gauges.
I installed an MRCOOL Mini Split on a garage which turned out very well and was much simpler compared to other kits.
It used 115-volt 20 AMP breaker the same as most home outlets.
MRCOOL has both 115-volt units and 230-volt units along with different sizes available.
Read Here For How I Installed a MRCOOL Mini Split Unit
Daikin is another A/C manufacturer that has been around for a long time and builds many good units, including mini split DIY kits.
They have differently sized units from 9,000 BTU – 24,000 BTU.
They use a copper line-set that will need a vacuum pump and gauges to pump down.
Many HVAC companies install Daikin since they are well-built units with a good warranty.
In fact, I once worked for an HVAC company that the owner would only install Daikin units.
There are many good units with Daikin one of the more trusted brands.
Read Here for Daikin Mini Split Unit Review and Installation
Mitsubishi is a company that is known for its well-built units and good warranties.
They have many split systems that can be installed, including the Hyper Heat model, which is designed for colder temperatures.
Most all mini split heat pumps work very well when cooling a space in the summer but can have problems in the winter if the temperature drops too much.
Heat pumps can struggle to heat during a very cold winter, with most units able to work down to -8, -10 degrees Fahrenheit.
The Mitsubishi Hyper Heat are heat pumps built to work in very cold climates.
If you have mild winters, such as in the American southwest, most any unit will have no problems heating.
But if you live in a colder northern climate, a Hyper Heat model would be a good option.
It also has a very good 26 SEER rating, making it one of the most efficient units available.
One downside to Mitsubishi units is cost; since they are such good units, they cost more.
They also are not as friendly for a do-it-yourself job and are meant for a professional to install.
They can be installed by an experienced homeowner who has installed a mini split before.
Anyone new to doing an install and looking for a DIY kit would likely be better off with one of the dedicated DIY kits.
Read Here for Mitsubishi Hyper Heat Unit Review and Installation
Mini Split Air Conditioners Comparison Chart
| Name | BTU's | Voltage | SEER Rating |
|---|---|---|---|
| Pioneer | 9000-36000 | 120V-220V | 19-23 SEER |
| Senville | 9000-24,000 | 230V | 20-25 SEER |
| Mrcool | 12,000-36,000 | 115V-230V | 17.5-19 SEER |
| Daikin | 9,000–24,000 | 230V | 17-23 SEER |
| Mitsubishi | 9,000–24,000 | 115V-230V | 26-30 SEER |
Can You Install a Mini Split System Yourself?
Yes, a DIY mini split system can be installed by any handy type of person looking to save on installation costs.
A good kit will come with everything for an installation except for the tools and electrical wiring.
There are several DIY kits available that come in all price ranges and SEER ratings.
How Hard is it To Install a Mini Split System?
Depending on your skill level with general construction installing a mini split can be hard or easy.
You will need to use drills, saws, along with HVAC tools such as a vacuum pump and gauges.
Installing a mini split requires running electrical from a panel, drilling a 3-inch hole in the wall, running control lines, a line-set, and more.
There are many YouTube videos to watch and see if you have the skill level to install a unit.
Calling an HVAC company and getting a quote to do an install likely is best for most people.
How Long Do Mini Split Air Conditioners Last?
Mini Split systems have a long lifespan, with the average unit lasting 15-20 years.
This is well above a traditional HVAC home system that lasts an average of 10-15 years.
Of course, how well maintained the unit is, and the climate will have an outcome for how long it will last.
Changing out the indoor filter and keeping debris away from the outside condenser should be part of regular maintenance.
Some brand names do last longer since they are better built, such as Daikin or Mitsubishi units.
With that said I have seen low-cost brand names keep working for many years and known brand name units break down.
If you have the money, one of the quality brand names, such as Mitsubishi, would likely be best.
The Pioneer or Senville units will likely be best if you are on a budget.
When installed properly and with the right maintenance, almost any mini split brand name will last many years heating and cooling.
How Much Does It Cost to Install a Mini Split Air Conditioner?
The cost to install a mini split can vary greatly since several things need to be considered.
- The average cost for a mini split unit is between $700-$2500.
- The average Do-It-yourself job costs $100-$500 for electrical and tools, plus the mini split unit.
- The average cost for an HVAC company to install a mini split is between $1000-$5000.
If you are a Do-It-yourself type person, a lot of money can be saved installing a unit.
The unit will need to be bought along with electrical wiring and tools.
There are many budget tools that can be used, which will bring the cost down.
If you plan on hiring an HVAC company to do the installation, the only way to know the cost is to call around and get quotes.
Every company and location will be different for how much they charge for an installation.
How a home is built, the location of the mini split, and the electrical panel will all be things to consider.
For example, a unit close to an electrical panel will cost less to run AC power compared to a unit far away from a panel.
Do You Need a Mini Split in Every Room?
HVAC systems are sized to the square feet of the space.
For example, a 700 Sq Ft home would need a unit rated for 18,000 BTUs.
Read Here for how to Size a Mini Split
Since mini split systems are ductless, they don’t push air on past walls and only cool the space they are in.
A large home with multiple bedrooms would benefit from multiple mini split units.
When mini split units are installed as the sole heating and cooling source in large homes, multiple units or zoned units are used.
For example, a 1500 Sq Ft home usually has 3-4 units strategically placed in different rooms.
A smaller house such as a mobile home will usually have 1-2 units.
Each home will be different and need to be thought out for the best install and setup.
Does a Mini Split Heat in the Winter?
A mini split heat pump unit will both cool in the summer and heat in the winter.
Notice the word Heat Pump.
As long as it is a heat pump, it has what is called a reversing valve that sends heat outside or inside on-demand.
This means that as long as the unit is a heat pump, it will heat and cool.
Most mini split units are heat pumps but be sure it is labeled as a heat pump.
One problem with heat pump HVAC systems is they don’t work well in very cold climates.
Most new units can work down to a -5/-10 degrees Fahrenheit before they start to struggle; of course, check the unit’s rating for temperature.
If the temperature drops too much, they will have difficulty pulling heat from the air, and the outside condensing coil will freeze up.
This makes them ideal as a heating solution in climates such as the American southwest.
For very cold climates, another heat source should be installed for very cold nights.
What is The Best Mini Split Brand Name?
With the many mini split system available, there is no single best brand name.
Every homeowner will have a different price range, installation, and climate.
For those who want the best brand name, warranty, and SEER rating mini split the Mitsubishi units are widely agreed to be the best.
They are more expensive compared to other packages and are not as DIY (do-it-yourself) friendly as many other kits.
Daikin is also a good brand name with a good warranty and costs less than the Mitsubishi units making them a good mid-range system.
Pioneer and Senville are budget systems built for the DIY individuals looking to save money and install the kits themselves.
MRCOOL is the best kit for the home do-it-yourself type person with their kits set up directly for a homeowner installing a system themselves.
All these units, when installed properly, will last many years heating and cooling.
Which mini split is the best will depend on how much you want to spend on a unit and if you install the system yourself.
Summary
The Pioneer, Senville, Daikin, Mitsubishi and MRCOOL Ductless Wall Mount Mini Split are good units with different sizes and voltages depending on the need.
The smallest unit is a 9,000 BTU with bigger sizes if needed.
There are many more units and simple ones that I have installed and worked well for me.
With the variety of different packages, there is no doubt a size that will fit any location it is needed in.
Installing a unit yourself is always an option if you have had previous experience with A/C systems and wiring.
Paying someone else to install the unit is a good idea if you don’t have any experience in HVAC, wiring, or construction in general, as there can be potential hazards.
As always, be sure to read the reviews on Amazon, forums, here, or elsewhere to be sure a unit is a good fit for you.
I need air conditioning added to a room and was told to get a mini split. The room is an addon and is 20 x 15 feet. What size mini split do I need to buy?
A 9,000 BTU unit is rated to cool 350-400 square feet. Your room 20 x 15 is 300 square feet.
Ok to all you expert HVAC persons…
The Mr cool lines are already vacuumed and charged so that’s why you can’t cut or shorten the lines? You just hook them up and turn out the valves and your done?
Yes, the lines are already sealed so they simply hook up. The Mr Cool lines are made of an easily bendable mesh with copper ends so they cant be cut. Other units use straight copper which can be cut and shortened with new flared ends.
Pioneers break every few months. They warranty the parts not the labor. You’ll spend more money on the labor to keep them running than they are worth.. that’s if you can find someone to work on them!!! Stay away. Go with a more reliable, popular manufacturer!
I installed a Pioneer 7 years ago and its still working great.
I am looking for a mini split for a garage in an ocean air setting. The Mr. Cool has a nice warranty (5 year parts 7 year compressor) and they market what is called Gold Fin condenser that is resists long term corrosion. Do you feel that this is more of a marketing thing or are the products better long term in ocean air? It is much more expensive than the Pioneer system and I’m trying to determine if it’s worth the extra cash.
I’m unsure of the best corrosion resistant mini split. I would go with the best warranty or the best budget unit that is low-cost to replace every 4-5 years. Let us know what you find.
They do not send you electrical because that is something in which its rules and regulations change from state to state. In Massachusetts, installing a minisplit that does not have existing electrical connections, requires a licensed electrician to connect the proper breaker in your panel and to run these new wire by federal state and local codes. I recommend checking on this. from what I understand if you go to sell your home after this you will be fined a significant amount of money for not using a licensed electrician or pulling a permit. This whole system is a catch 22 because you are technically not allowed to do this unless you have a Valid EPA Clean air certificate ( however, ive never seen nor do I even know who to report that to, I don’t believe that it is enforced very well.) but this is all stuff we learn in the first 5 minutes of hvac school. (in mass anyways) I understand it is slightly different from state to state.
They also don’t know what to send you based on your needs, This is a terrible system to install even if your looking for the minimum cost for zone heating and cooling, It sounds great, but you can google everything im telling you. These systems design which allows you to “do it yourself” works, but is not ideal, the problem is the risk of system contamination during install. These pre charged lines are not customizable in length you get what you get and have to make it work. Also there are many things not in the book that needs to be accounted for if you intend to get any longevity out of this product. 5 years limited 7 year registered warranty (on compressor) is TERRIBLE COVERAGE, has anyone compared it to daikin, Mitsubishi, fujitsu any other manufacturers warranty? The problem with these systems and I have already replaced 2 of these, as well as had countless service calls for them, Almost every time the issue is between 3 and 6 years the system stops working usually do to a restriction in the outdoor unit, this system has a series of internal filter driers (strainers) inside of the copper lines in key places, and these are the only defense against moisture, since your lines come pre-charged and you cannot purge or vac. as recommended. So what happens is the system will function with small un-noticeable amounts of moisture(aka non condensables) which will if your lucky make its way to the compressor and seize that since that is one of the only things covered under warranty…. but unfortunately what is more likely happening the strainers and internal filter driers are getting clogged, and or the moisture is grouping freezing and creating blockages in the line. This is a SERIOUS problem for this system design, due to the sealed pre-charged lines this essentially means replacing the lines and or system one or both units. The do it yourself design makes service nearly impossible on this system. All I can say is if you buy this expect it to last 3 or 4 years and expect it to cost more to fix than it did to install. and you might as well forget about that warranty, even the things they do cover, they will deny you for because you haven’t been doing the recommended manufacturers 2 times a year maintenance. Its one hell of scam, if you want a cheap minisplit, you can get that from a pro, with warranty and at a very competitive price, with twice the efficiency at least, twice the warranty, for less than twice the price. Also some smaller companies will let you do certain things your own to save on labor if you are mechanically inclined and desire to do some work yourself, but we would choose what to have you do basic things like setting units in place, or finishing touches to clean up the appearance etc… Many of the companies in Eastern mass anyways are willing to work with you, and are happy to get a little help on certain parts of the install, preparations etc…
I have not seen one comment from a professional that is not agreeing with all or at least in part, what I am trying to warn. In the end of course make your own decision, I’m sorry if I am offending anyone, just as a professional of the trade, a small business owner, and direct experience with these systems I feel I have an obligation to my region to warn, notify, share my opinions whatever you want to call it , I just cant sit back and watch so many people jump on this train, when I personally have several customers who feel they were entirely scammed by this product. It can be very misleading and mis-informing. It can go well but from what I have seen is not the norm. Im seeing these systems life span at ONLY 3 to 6 years.
You can you tube “how to evacuate an ac system” , “essential preparations to mini split install”. etc… This is the last comment I will make on this matter.
There is no certification requirement since the refrigerant is sealed in the unit. I have installed several mini split systems over the years using different manufactures and have never had any issues. All the units are still working great. My favorite is Senville but Pioneer other units are also good. Your comment is just misinformation.
Good blog post Aaron. I’m looking at a DIY mini-split for our 40+ year old home with aged ducts and a defunct AC compressor. A couple of units would get us by for the thirty some days a year we actually need air conditioning. The local AC contractors are quoting from $7K to $19K for a complete central air change out. Most want to abate the old asbestos insulated ducts that still work, and replace the old updraft gas furnace that still works great. I figure I can install 3 split units to do what we need for less than half of what these contractors want for a system, and then there’s no guarantee it won’t break down or cost me a fortune to run.
So, since I’ve built a couple of houses, a couple of boats, a car or two and an airplane, I figure I can install a minisplit. LOL
What is the warranty policy from both Pioneer and Senville for DIY? Some of the manufacturers won’t warranty their units if you DIY. Mr. Cool is easy to get out here but 50% more expensive than a unit that does not have pre-charged linesets. You can buy a nice robinaire 2-stage vaccum pump from amazon for about a hundred bucks, and a gauge set isn’t much more.
Do I need a micron gauge? If I get stuck I can call a pro, but some seem reluctant to work on a DIY system, or want to charge a grand to show up.
Can you comment? I’m really torn about this. We’ll likely only stay in this house for the next five years, fast approaching retirement and won’t be able to afford to stay in So-Cal once the money flow stops. LOL
Thanks!
Installing 2-3 mini split units sounds like a good option and what many HVAC companies will likely recommend. The units are currently listed as warranted. Be sure to check for how long when buying encase it changes.
So far I have not had any problems so have not had to deal with any warranty and it may be best to read the comments on Amazon to see if anyone had to deal with a return.
I used a cheap vacuum pump and HVAC gauges to pump the unit into a vacuum. It is easy enough to do and I doubt you will have any problems since you have built homes before.
Let us know how it goes
I would like some advice on placement and type of indoor unit in a 600 sq ft house. The layout is front half is 1 open vaulted room with 12′ peak ceiling. Back half of house is two small bedrooms with 8′ ceilings and a hallway bath. Do I place one unit in the big room on a exterior wall or a one ceiling unit in the center hallway that has attic access?
Daikin prob one of the best mini splits on the market and my top 3 are Daikin , Fujitsu and Mitsubishi
After reading the reviews on the Pioneer mini split I decided on the 220 volt 12,000 unit. From what I have read 220 volts operates more efficiently than 110 volts over the long term.
Mini-splits are the best cooling systems as someone who has traveled internationally to many locations I can tell you they are used around the world for a very long time now. When properly installed they are very efficient which is great for lower monthly bills. And yes they are so quiet, especially the newer ones. It is best to plant some shade or build a small cover for sun relief on the outdoor unit such as lattice. It will not only help it operate more efficiently which will also help cool the building. In fact shade can significantly lower temperatures which also prolongs a units life.
I’m looking for a small mini for my boondockin rv I’m very interested in a 110/120 volt 9000 btu , I’m only interested in a super energy efficient one ,one like the Diy Mr Cool at 9000 btu ,25seer would be sweet ,but I guess I’m dreaming, which one would you recommend ? Thanks 😊
We have a multi-zone system with 3 outdoor condensers and 9 indoor units. They are all Mitsubishi Hyper-Heat units.
After having the for roughly a year they are amazing. Power bills are 35% lower during the summer than our previous unit. We live in Texas so summers can be pretty brutal.
They also heat in the winter and work great but our winters are mild compared to northern states. They can provide 100% heating capacity down to 8*F and still provide some heat all the way down to -10*F.
Overall I have been super satisfied. Every room has its own thermostat control and scheduling so I can turn off or adjust rooms when not being used.
I doubt there’s any way our HSA would allow us to install these. They won’t allow window AC units so I’m guessing this is just as bad in their eyes. Unless maybe it is an emergency waiting on AC to be repaired.
I have worked in HVAC for awhile and installed many of these. One thing I would suggest if you live in a region that could receive snow is to install risers to keep the unit elevated. This is needed to help protect the fan and keep the unit from freezing up while in heat pump mode.
Nice post! Thank you so much for the info. I was really looking for some tips on choosing the best mini-split sir conditioner. So lucky I found your blog. It is full of useful and interesting facts.
Hello Aaron. Thank you very much for your post. I would like to know if you could look at the floor plans of our earth dome (three barrel vaults) and help me decide what units to buy. We have already an air recovery system and in line dehumidifiers. We do not have ceilings so it is a bit peculiar. It is a cool demo project as we are pioneers in SW Florida for this type of construction. I am sure you would love to see pictures and the blue print too. Let me know. Thank you.
Want to buy a new version of the air conditioner like Pioneer Air Conditioner Inverter+ Ductless Wall Mount Mini Split System Air Conditioner, Thank you for a good read I found this blog useful.
I have a long line set and need to add additional refrigerant. How do I do that?
Using 3/8 LIQUID line, add .6 ozs per foot OVER the excess tubing from the unit factory charge.
Factory charge WILL be different from manufacturer to manufacturer. Some charge for 15 foot while others charge for 20 foot and others may even charge for 25 foot. That you will need to know.
Subtract the extra tubing length from the factory length listed on the equipment. Multiply the extra length times .6 to get adjusted charge for tubing size.
25 feet times .6 ozs equals 15.0 ozs. Divide this by 16, which is the number of ounces in a pound and you will get the amount needed for extra line set.
Can I install ventilation ducts with this ? I plan on using for entire house 36000 btu version. Need it to make it to 3 bedrooms.
I want to install (DIY) a mini split AC in my 235 square foot master BR. The easiest DIY seems to be the Mr Cool, but they only go down to 12000 Btu and I probably only need 6-7000 Btu. If I go with the Mr Cool, will the unit cool my bedroom so quickly that it will cycle on and off a lot—-making more noise? Should I not consider this one and rather look at others? Others that might be DIY possibilities only seem to offer 9000 Btu as the smallest. Thanks for any help. Dennis
Any chance you can put a better photo of the HVAC wiring? More at an angle? Can”t really see conclusively which wires are connected to which terminals. Maybe a photo of the humidifier end of it too. I”ve installed my own humidifier and various thermostats, figuring out all the wiring myself. Curious to see if anything jumps out at me if I can see the connections better.
I am an ex-pat living in Mex. My 1 ton LG quit on me the end of last summer. I was told by 2 AC shops here it would be cheaper to buy a new one than repair the old one. I have been shopping for a new one and today at a large chain store I looked at several brands at the low end prices and most were in the $5,500 peso range (more or less $300US. I had been told by 2 reputable AC shops that it would cost about 1000 pesos to install one. But the store had a Westinghouse 1 ton for 5,500 pesos but were having a promotion and installation was free. But in the back of mind I thought I remembered something about Westinghouse”s reputation had fallen into the sewer over the last few years. I came home and checked WH mini-splits on the net. I had trouble finding anything and then found customer comments on Amazon website. there were 3 reviews and they were all 3 star and the reviews were not good. Amazon said that it was no longer available and didn’t know if or when it would become available. What do you know about Westinghouse mini-splits? I live on my Social Security and watch every peso I spend but I think I am going to pass on the promotion and buy a cheap one with better customer reviews and just pay the 1000 pesos for an installation.
i get conflicting reports on what size i need. i live in Texas got a 600 square foot home open concept just 1 person. it gets hot hot hot lol. i have installed new insulation and walls only has 1 window and no basement or attic what would u recommend ? hear 12000 from some and 18000 from others, torn between going pioneer senville and the Mr cool. thanks in advance for any info
A 12,000-14,000 BTU unit should keep a well insulated 600 Sq Ft space cool even on hot days. Of course insulation is a big factor. A well insulated 600 Sq Ft home should have no problems staying cool with a 12,000 BTU unit, if in doubt go for a larger 14,000 BTU unit. If the space is not well insulated a 18,000 BTU unit would likely be best.
Let us know how it goes.