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Calculation Machine

Portable AC Sizing Calculator

BTU sizing for a portable air conditioner.

Reviewed by the Calculation Machine team · How we check our maths

Your values

ⓘ Live results

Results
Recommended rated BTU
9,375 BTU/hr
Equivalent tons
0.78
Note
Single-hose units depressurise the room, pulling in unconditioned air

Quick answer

Portable ACs need roughly 20-25% more rated BTU than a split system for the same room because of single-hose exhaust losses.

The formula

BTU = area x 25 x sun factor x hose factor

Worked example

Worked example

Using the values the calculator loads with.

Inputs

  • Room area300 sq ft
  • Sun exposureAverage
  • Hose typeSingle-hose

Result

  • Recommended rated BTU9,375 BTU/hr
  • Equivalent tons0.78
  • NoteSingle-hose units depressurise the room, pulling in unconditioned air

How to use the Portable AC Sizing Calculator

  1. 1Measure the room's floor area.
  2. 2Adjust for sun exposure since glass adds significant load.
  3. 3Add a hose-type penalty — single-hose units need extra capacity to offset negative pressure infiltration.

Frequently asked questions

Why do single-hose units need more BTU?

They exhaust room air outside without a matched intake, pulling warm outside air back in through gaps.

Can portable ACs replace central air?

Only for small or supplemental spaces — they are far less efficient per BTU than split systems.

About this calculator