What Size Mini Split Do You Need? BTU Sizing Chart

By | January 7, 2020

BTU Sizing Chart for Mini Split HVAC Units
Mini Split HVAC systems are great for heating and cooling and are very versatile able to be fitted into most any space.

Besides picking the right mini split manufacture how big a unit is needed also needs to be considered.

This is easy to do by calculating the square feet of the space to be maintained.

How to Get a Rooms Square Feet
To get the square feet of a room measure the length by the width and multiply the two together.
What Size Mini Split Do You Need
For example, a room that is 20 feet long by 20 feet wide would be 20 X 20 = 400 Square Feet.

If there are more rooms such as closets simply do the same and add them to the total.
 




 
BTU Sizing Chart for Mini Split HVAC Units

Area Size Sq FtBTU's Needed
150 to 250 Sq Ft6,000 BTUs
250 to 300 Sq Ft7,000 BTUs
300 to 3508,000 BTUs
350 to 400 Sq Ft9,000 BTUs
400 to 450 Sq Ft10,000 BTUs
450 to 550 Sq Ft12,000 BTUs
550 to 700 Sq Ft14,000 BTUs
700 to 1,000 Sq Ft18,000 BTUs
1,000 to 1,200 Sq Ft21,000 BTUs
1,200 to 1,400 Sq Ft23,000 BTUs
1,500 Sq Ft24,000 BTUs

Take Into account Insulation and Climate
How well a home is insulated as well as the climate should also be considered.

For example, a home poorly insulated will need a bigger unit than a home that is well insulated.

Climate should also be considered mainly in locations that extreme cold weather happens.

Most any mini split will have no problems cooling a space in air conditioner mode but may have problems heating in extremely cold climates.

Heat pump mini split units that both heat and cool reverse the air conditioning mode to heat during the winter.

This means they pull heat from the surrounding air which becomes more difficult as the temperature drops.

Most modern units will have no problems down to 10-20 degrees Fahrenheit but will start to struggle if the temperature gets much colder.

If the outside temperature becomes too cold the outside condensing coils will freeze up with ice.

When this happens a Heat Pump unit will go into what is called defrost mode.

Defrost mode is basically turning the air conditioning on to melt the ice off the outside coils.

Once the ice is melted off defrost mode will turn off and the unit will start heating again.

Often when it becomes very cold heat pumps will cycle between heating and cooling.

For example, if you live in Alaska or a climate with very cold winters you will have no problems cooling in the summer, but the heating will stop once the temperature drops too much.

If you live in the American southwest such as Nevada, Arizona, or Texas it will have no problems heating or cooling with heat pumps ideal for climates such as the American Southwest.


 




 

16 thoughts on “What Size Mini Split Do You Need? BTU Sizing Chart

  1. Gail Caron

    I really need some help. Last year, I had an addition built on my home in southern NJ as a weaving studio. The main room is 480 sq ft (20×24). It has a peaked ceiling that is 20 feet at the highest point. There is a small room (8ftx8ft) attached with a sliding door in between. The HVAC contractor hired by my general contractor installed a 3 ton Fujitsu Halcyon outside unit, a 24000 BTU unit in the studio at about 12 feet high. In the small room there is a 9000 BTU floor mount unit. Both units are run by the same outside unit.

    From the beginning, I have been complaining about the humidity which sometimes exceeds 80%. The best that I can do is about 63% RH if I have the temperature down to around 68 degrees in the studio. At times, there is water dripping from the fins at the bottom of the unit. In the small room, the humidity is usually higher than the temperature. Sometimes there is actually fog in that room.

    The contractor keeps telling me that everything is working fine but my construction is so tight and the units are so efficient that they do not run long enough to remove the humidity. That cannot be how the system is supposed to work. Fujitsu is about useless as far as customer service. I am positive that the system is oversized and finally contacted other contractors. They have all said that it is, but do not want to get involved in a dispute with the original contractor. Can you point me to someone who can walk me through a load calculation so that I can have something to stand on? Thanks.

    Reply
  2. krissy krotzer

    Hi I live in MN, in a mobile home. I need to heat 6 rooms, four of them are bedrooms about 200sq. feet each and are pretty well insulated. the other two are conjoined with a door way but no door and they are about 800sq feet and not insulated well at all. Can you tell me what btu I would need for each room. It gets really cold her sometimes -30

    Reply
  3. Tim Lyons

    Hello, I have a 650 sqft cabin, 2 bedroom 1 bath. I would like to use a mini split for heat. We are in the Seattle area and cooling is not the main reason for the unit. Will an 18k btu unit be able to heat the space. It doesn’t get to cold, low 20’s at worst.

    Thanks for any help you can give.

    Reply
  4. Bill Brannon

    I am wanting to use a MrCool mini-split heat pump in a 376 sq. ft. building that is constructed out concrete block. It also has 9 foot ceilings. The ceiling is a drop grid ceiling with acoustic tile without insulation above it. This building is located in the deep south with high summer temperatures and very high humidity.
    Considering the concrete block construction and location, will a 12000 btu be enough? I have considered going to btu but am afraid that will be too large and cause the unit to satisfy the call for cooling too soon thus causing it to not remove the humidity effectively.

    Thank you

    Reply
  5. Roslyn Johnson

    Would a 9,000 BTU mini split work for a small well insulated 425 sq. Ft. Mobile home in Southern California.

    Reply
    1. Bobby

      For many Southern California multi-family projects, around 400 sq. ft./ ton is kind of an average for moderate climate zones (there are 16 in CA). More wall exposures/ windows would drive that towards 300-350 sq. ft./ ton, and mild climate zones like Long Beach tended to be around 500 sq. ft./ ton. When you say well insulated, the roof is probably your biggest cooling load besides the windows. Blackout shades/ curtains would help, particularly on E, W, and S exposures, and exterior shades would help even more in the event hot weather is an issue (awnings as well).

      3/4 ton to 1 ton sounds ok to me. Ask whether the mini split has turndown capability, meaning that it has multiple speed fans and can run at partial capacity. Then I’d go with the 1 ton or 12,000 Btu. Most HVAC contractors can run a heating/ cooling load calculation for you as well, modeling your conditions/ climate zone.

      Reply
  6. Jonathan

    I appreciate the info on your site. I need to heat and cool a room that is 22.5′ x 22.5′ (506 sq.ft.) with 6″ fiberglass in the walls and ceiling, but ceiling is 10′ high. When determining needed BTU, do you take into account the added cubic feet of the higher ceiling and therefore would you need more than a 12,000 BTU unit? I am in the deep South. Thanks.

    Reply
  7. Willis Penfield

    I have a cottage one large room downstairs a master bedroom full bath and a small bedroom upstairs about 800 square feet overall do you think a 12 plus 12 would work well one downstairs and one in the hallway maybe a cassette upstairs and a floor unit downstairs need heat also man who rents likes it hot in winter and cold in summer

    Reply
  8. Thomas C Bridges

    I am building a new Carriage house near Nashville, Tn The first floor is 1400 sq ft 3 car garage Insulated and drywall ed. Second floor is a main area open concept kitchen,Living room and dinette its estimated at 860 sq ft. Bathroom will have its own heat bedroom is 540 sq feet divide wall between the hole area is only 8 ft. so clear height on roof is a !2/12 pitch. Really need help on how to set it up with just Mini system.
    Thanks, Tom

    Reply
  9. david

    need to know what size I need, I live in texas so ya know its hot lo, also its 600 square feet and has 1 window. open concept house its going in. well insulated new sheetrock and insulation no attic or basement.

    Reply
    1. Aaron Benetti Post author

      A 12,000-14,000 BTU unit should maintain a well insulated 600 Sq Ft home even on hot days.

      Reply
  10. Tony Dunlap

    Can I get a smaller unit if I have 3.5 inches of foam in the wall, 9.5 inches of fiberglass in the floor and 2.5 foot blown fiberglass in the ceiling. Area is 495 sq ft and has 7’8″ ceilings. Temp range is -10 to 95. High seer preferred.

    Reply
    1. Aaron Benetti Post author

      If a space is well insulated you likely can get a smaller unit depending how extreme the weather is.

      Reply
  11. Deeana

    Hi,
    I’m considering a Mrcool mini split for my double garage. I live in San Francisco East Bay Area and my garage faces South-West. It’s under 500sf with 8 ft ceiling. The sumner temp can reach up to 110 F and we have fair insulation in the garage. I’m wondering if a 12000btu unit will be effective enough for the space.

    Thanks.

    Reply
    1. Clay Tammaro

      Hi my sunroom is120 sq ft with 10’ceiling. 1/3 of room is glass on 3 sides. Roof,hip walls and walls are well insulated. Sunroom faces south east. I need to cool and heat space, my area goes from -0f to 100f. Could you help with btu size.

      Reply

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