Tool
BTU Check
A portable air conditioner box carries two capacity numbers for the same machine, and the larger one is the one printed in the product name. This works out a range in the smaller units and tells you which figure on the spec sheet to hold it against.
Floor area of the room
Direct afternoon sun
A window the exhaust hose can reach
Which number to read on the box
5,000 to 6,500 BTU SACC
Compare that against the smaller figure in the specifications, not the larger one in the product name. The two describe the same machine measured two different ways.
The arithmetic came out below the band shown, and the band has been held at the bottom of what this catalog stocks: 5,000 BTU SACC is the smallest SACC figure any listing here states.
Stated SACC figures in this catalog near that rangeBLACK+DECKER Portable AC, 9,000 BTU at 5,300 BTU SACC; Midea Portable AC, 8,500 BTU ASHRAE at 5,000 BTU SACC.
The arithmetic, in full
- Base load = floor area in square feet × 20 BTU/h per square foot, read as a SACC figure.
- If the room takes direct afternoon sun, add 10 percent to the base load.
- Round the result to the nearest 500 BTU.
- Open a band 1,500 BTU wide, starting at that figure.
- Hold the whole band inside the 5,000 to 12,000 BTU SACC span the listings in this catalog state — both ends of that span are read off the data rather than typed in.
Worked for this selection: 200 sq ft × 20 = 4,000 BTU, with no sun uplift applied, rounded to 4,000 BTU.
What it does not account for: ceiling height, insulation, how many people are in the room, heat given off by equipment, how well the windows seal, or what the sun does to the wall rather than through the glass. It is a starting figure for reading a spec sheet, not a load calculation.
The exhaust has to leave the building
A portable air conditioner does not make cold air. It moves heat out of the room through a hose, and the hose has to reach a window. Venting it into the same room, into a closet, into a hallway or into a ceiling space puts the heat straight back where it came from.
The hose runs hot in normal operation. Keep it away from bedding, curtains and furniture, and keep the run as short and as straight as the window allows. If the room has no window the hose can reach, a vented portable unit is not the answer for that room — and an evaporative cooler is not a substitute, because it publishes no BTU figure, removes no heat from the space, and adds humidity to it.
Why there are two numbers at all
Two test procedures exist, and they measure the same machine under different conditions. The ASHRAE figure is the older method and reads higher. The SACC figure comes from the Department of Energy procedure written for this appliance category, accounts for heat a single-hose unit pulls back into the room, and reads lower. Across the five vented units in this catalog the SACC figure sits between roughly 59 and 86 percent of the headline number.