BTUFit › Mini split sizing › 1,000 sq ft
What size mini split for 1,000 sq ft?
Quick answer: a 18,000 BTU head. The cooling load for 1,000 sq ft under standard conditions is about 18,000 BTU/h, and 18,000 BTU is the head size that covers it. Sun, ceilings and heating duty move the answer; the table and calculator below cover those.
| Scenario | Load (BTU/h) | Head size |
|---|---|---|
| Standard room (8 ft ceilings, average sun) | 18,000 | 18,000 BTU |
| Very sunny | 19,800 | 24,000 BTU |
| 10 ft ceilings | 19,800 | 24,000 BTU |
| Heating too, mild winters | 20,700 | 24,000 BTU |
| Primary heat, cold climate | 25,200 | 30,000 BTU |
At 1,000 sq ft the arithmetic says one 18,000 BTU head and the floor plan usually says otherwise. An 18k head does cover the load, but only if the 1,000 sq ft is a single volume. A typical 1,000 sq ft floor is four or five rooms, and a head in the living room does nothing for a bedroom behind a closed door in July.
The multi-zone alternative at this size is a two or three zone condenser, and the head combinations are not arbitrary. A 2-zone 18k outdoor unit is normally sold as 9k + 9k or 12k + 9k. A 3-zone runs 9k + 9k + 9k, or 12k + 9k + 6k, on a 24k or 27k condenser. Notice that 12k + 9k is 21,000 BTU of heads hanging on an 18,000 BTU condenser. That is deliberate. Multi-zone condensers are rated to carry more branch capacity than they produce, often up to about 130%, because the heads do not all run flat out in the same hour.
What you give up is the bottom of the range. A multi-zone condenser has a higher minimum output than a single-head inverter, so on a mild October evening with one bedroom calling, it cycles instead of loafing along. A single 18k head throttles further down and holds a steadier temperature in the one room it serves. Every extra head is also a wall penetration, a condensate path, and a filter somebody has to remember to clean.
Voltage, unlike the 500 sq ft step, is not a decision here. 18k heads and every multi-zone condenser worth buying are 230V, so a dedicated circuit and a disconnect are in the job whichever way you go.
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Installed cost ballpark for 1,000 sq ft (US, 2026): a single 18,000 BTU head install commonly falls in the $3,000–$6,000 band when the space is truly open. Multi-zone (one outdoor, several heads) for a floor of rooms runs higher. DIY language only applies to pre-charged / quick-connect kits; 230V work goes to a licensed electrician. Labeled national estimates, not a local bid.
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Frequently asked questions
Is one 18,000 BTU head enough for 1,000 sq ft?
If the 1,000 sq ft is genuinely open, yes: the load is about 18,000 BTU/h and an 18k head covers it. If it is four or five rooms, no, and no amount of extra capacity fixes it, because air from one head does not cross a closed door. Count doorways before you count BTUs.
What head combinations come on a multi-zone at this size?
A 2-zone 18k condenser is usually sold as 9k + 9k or 12k + 9k; a 3-zone as 9k + 9k + 9k or 12k + 9k + 6k on a 24k or 27k outdoor unit. The heads are allowed to add up to more than the condenser is rated for, often to around 130%, because they do not all run at full output at once.
Does a multi-zone cost more to run than a single head?
At part load it often does. A multi-zone condenser cannot turn down as far as a single-head inverter, so with one bedroom calling on a mild evening it short-cycles rather than running slowly. The multi-zone wins on the thing that actually bothers people, which is the bedroom that never gets cold, so this is a comfort-versus-efficiency trade rather than a mistake.
How much does a mini split cost installed for 1,000 sq ft?
A single 18,000 BTU head install commonly lands in the $3,000–$6,000 band when the space is truly open and the wall path is simple. A multi-zone system for a floor of separate rooms runs higher, and the gap widens with each head. DIY pricing only applies to pre-charged kits; the 230V circuit goes to a licensed electrician either way. Labeled 2026 national range, not a bid.