ZoneBtuBTU per head, per room, per orientation — not one number for the house.

What size mini split does a 200 sq ft bedroom in Shreveport, LA need?

200 ft² bedroom in Shreveport, LA
6,000BTU/hr
5,229 BTU/hr of load at 26.1 BTU/ft² — the figure for 2,985 cooling degree days
200 ft² bedroom in Shreveport, LA6,000 BTU/hrHead size to buy5,229 BTU/hrCalculated load4,000 BTU/hrWhat the 20 BTU/f…
Head size to buy6,000BTU/hr
Calculated load200 ft² × 26.1 BTU/ft²5,229BTU/hr
BTU per square foot hereinterpolated from Shreveport's 2,985 cooling degree days26.1BTU/ft²
What the 20 BTU/ft² rule givesthis room needs 31% more than the rule says4,000BTU/hr
Summer design temperature99°F
Winter design temperaturea mini split heats too — this is the number that decides whether it can carry the room alone24°F
Summer day–night swinga fairly dry climate20°F
Days at or above 90°F103days/yr
Oversize from the size stepwithin the normal step15%

Notes

  • The "20 BTU per square foot" rule is a Midwest number. Shreveport runs 2,985 cooling degree days, which works out to 26.1 BTU/ft² — so for this bedroom the rule is 31% short. A single national figure has to be wrong somewhere, and this is where.
  • Bedroom: the room where oversizing hurts most — quiet, low load, long runtimes wanted.
  • 6,000 BTU/hr sits close to the load, which is where a mini split works best. Inverter equipment is happiest running long and slow at part load; it is the short, hard cycles of an oversized head that leave a room cold and damp.
  • Shreveport is fairly dry — summer nights stay within 20°F of the day's high, the signature of humid air. A meaningful share of this head's work is removing moisture, and it only removes moisture while it is running. This is the climate where an oversized head produces a room that reads cold and feels clammy.
  • Do not forget the winter side. Shreveport designs to 24°F. A cold-climate rated head will hold most of its capacity there, but a standard one will not — ask for the capacity at 24°F in writing.
  • Where these numbers come from. Shreveport Regional Airport, 71 km from downtown Shreveport, daily records 2015–2024. Design temperatures are calibrated against published ASHRAE values at eight airports and land within about 2°F of them.

The short answer

A 200 square foot bedroom in Shreveport, LA needs a head of about 6,000 BTU per hour. The calculated load is 5,229 BTU/hr.

Where that number comes from

Shreveport, LA runs 2,985 cooling degree days a year, which puts the room at 26.1 BTU per square foot rather than the 20 BTU/ft² the generic charts use. Applied to this room the rule gives 4,000 BTU/hr.

The winter half of the question

Shreveport, LA designs to 24°F. A mini split is a heat pump, and its heating capacity falls as the outdoor temperature drops — the nameplate is measured at 47°F, not at the temperature you actually need it.

Sizing a single room is not sizing a house

There is no other room to absorb a mistake. An oversized head short-cycles, never runs long enough to dehumidify, and leaves the room cold and damp.

Nearby sizes

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