Sizing Guide
What Size Mini-Split Do I Need? A Sizing Guide for East Texas Homes
Mini-splits are sized in BTUs, and the square footage of the room is only the starting point. In East Texas, sun exposure, insulation, ceiling height, and humidity decide whether a room needs a small head or a large one. Here is how sizing works, what changes it in a Tyler home, and when a mini-split is the wrong tool altogether. Call 903 HVAC at 903-393-1044.
Proper Manual J Sizing on Every Installation
The short answer: start with the size of the room, then adjust for how the room is built and where it faces. A 300 square foot bedroom on the north side of a well-insulated house and a 300 square foot bonus room over the garage with west-facing windows are not the same load, even though a chart would give them the same number. That is also why "what size mini-split for a 2,000 square foot house" has no single answer. A whole house is several rooms with different loads, and the right answer is a room-by-room calculation, not one big unit.
Mini-Split Size by Room Square Footage
The table below is the common starting point for a single room in a hot climate. Treat it as the first draft of a number, not the final one. The adjustments that follow are where East Texas homes usually move up a size.
| Room Size (Sq Ft) | Starting Capacity (BTUs per Hour) | Typical Room |
|---|---|---|
| Up to 250 sq ft | ~6,000 to 7,000 | Bedroom, home office |
| 250 to 400 sq ft | ~8,000 to 10,000 | Large bedroom, sunroom |
| 400 to 550 sq ft | ~12,000 | Living room, converted garage |
| 550 to 800 sq ft | ~15,000 to 18,000 | Open living and dining area, shop |
| 800 to 1,200 sq ft | ~18,000 to 24,000 | Large open floor plan, lake-house addition |
| 1,200 to 1,500 sq ft | ~24,000 to 30,000 | Small whole home, usually as multiple heads |
These figures are a rough starting point for a single conditioned space. One ton of cooling equals 12,000 BTUs per hour, so a 12,000 BTU head is a one-ton unit.
East Texas Adjustments That Change the Number
The chart assumes an average room. Most of the rooms we are asked to cool in Tyler are not average, and these are the conditions that push the size up or down:
- West-facing windows. A room that takes the afternoon sun carries a heavier load than the chart suggests. The common rule of thumb adds about ten percent of capacity for a sunny room and takes about ten percent off for a heavily shaded one.
- The room over the garage. Heat comes up from the garage below and down from the roof above, and the walls often have less insulation than the rest of the house. These rooms are the most common case where the chart undersizes.
- Uninsulated shops and garages. A metal shop or an unfinished garage gains heat far faster than a finished room of the same size. Insulating first is often the better investment, and the sizing changes once it is done.
- Lake-house additions with a lot of glass. The view rooms at Holly Lake Ranch and Emerald Bay are built around windows. Glass area, not floor area, drives the load in those rooms.
- Kitchens. Cooking adds heat that a bedroom never sees. Room-by-room sizing guides usually add several thousand BTUs for a kitchen.
- Ceiling height and occupancy. The chart assumes standard ceilings and a couple of people. A vaulted ceiling or a room that regularly holds a crowd needs more.
Why Tyler Is Not the National Chart
Most sizing charts online are written for the whole country. East Texas summers run long and hot, with stretches of 100 degree afternoons in the worst years, and the humidity is the part that charts miss. A mini-split does two jobs here: it lowers the temperature and it pulls moisture out of the air. A unit that is too large cools the room quickly and shuts off before it has run long enough to dehumidify, which leaves the room cool but clammy. That short cycling also wears the compressor. In this climate, the right size is often smaller than a nervous homeowner expects, and bigger is not safer.
Spring adds one more local wrinkle. Pine and oak pollen in March and April load the filter in a mini-split head faster than most people expect, and a clogged filter cuts the capacity of a correctly sized unit. Cleaning the washable filters through pollen season keeps the unit performing at the size it was chosen for.
Single-Zone vs. Multi-Zone
A single-zone system is one outdoor unit and one indoor head. It is the right tool for one problem room: the addition, the shop, the bonus room, the sunroom. It is sized to that room and nothing else.
A multi-zone system runs several heads from one outdoor unit. It works well for a small home without ducts or for a group of rooms that are used at different times. The sizing trap is that multi-zone outdoor units come in fixed capacities, and the heads on them have minimum sizes. If the smallest available head is larger than a bedroom needs, that room ends up oversized, and the short-cycling and humidity problems above show up in every bedroom on the system. When we design a multi-zone system, we size each room first and then choose the combination of heads and outdoor unit that fits, rather than picking a big outdoor unit and dividing it up.
When a Mini-Split Is the Wrong Tool
If you have a whole house with ductwork in good condition, a central system is usually the better answer, and a mini-split in every room costs more and looks busier than one central unit. Ductless earns its place where ducts do not exist, cannot be extended, or serve one area badly. Our guide on mini-split vs. central air compares the two in detail. Sizing a mini-split for a room that a central system could serve does not fix the underlying duct problem, and we will say so.
How 903 HVAC Sizes a Ductless System
We run a Manual J load calculation for ductless installations the same way we do for central systems. It accounts for insulation, window area and direction, ceiling height, and the East Texas design temperatures and humidity, and it gives a BTU figure for each room rather than a guess from square footage. From there we match the load to the Samsung wall-mounted heads we install, which come in a range of capacities from small bedroom units up to sizes that handle a large open room. Price is set by the capacity, the number of zones, and the installation work, which is covered in our guide on what drives the cost of a mini-split. Details on the systems and the installation process are on our mini-split installation page, and once the system is in, seasonal cleaning is covered under mini-split maintenance. If you are sizing a central system instead, start with our guide on what size AC you need.
Want the Room Sized Right the First Time?
Get a load calculation for your addition, shop, or lake house from a woman-owned, family-run East Texas team with over 40 years of experience.
903-393-1044 Book Your ServiceFrequently Asked Questions
There is no single number, because a 2,000 square foot house is several rooms with different loads. A whole-house ductless system is designed room by room, with a head sized for each space and a multi-zone outdoor unit chosen to match the total. A Manual J load calculation gives the figure for each room, and we run one before recommending a system.
A mini-split is the right tool where ductwork does not exist or cannot reach: an addition, a converted garage, a shop, a sunroom, or a room the central system has never cooled well. If your house has ductwork in good condition, a central system is usually the better choice for the whole home. We will tell you which applies to your house before quoting either one.
We do not recommend it. Handling refrigerant requires EPA Section 608 certification, the line set has to be evacuated and charged correctly for the unit to reach its rated capacity, and most manufacturers void the warranty on a system that was not installed by a licensed contractor. A poorly installed head also runs undersized no matter what the label says.
No. An oversized mini-split cools the room quickly and shuts off before it has run long enough to remove humidity, which leaves an East Texas room cool but clammy. The frequent starts and stops also wear the compressor. The right size runs longer at a lower speed, holds the temperature steady, and keeps the humidity down.
