It takes a certain sized portable air conditioner (BTU output) to cool a certain sized room – but how do you know what size A/C unit to buy? You don’t want to overkill it with a unit that’s too large or else the compressor will turn on and off too often, which wears it out. Obviously, choosing a model that’s too small won’t cool the room.
Turn to the manufacturers and retailers, of course. The product specs and descriptions should tell you how large a room a certain model will cool. Usually this is measured in square feet, and it assumes the room’s ceiling is 8 feet high. Naturally, a room with an open doorway or wall, poor insulation, many windows, direct sunlight, a fireplace, or even a few dogs residing within will make it harder to cool, and there are no solid recommendations about how many BTU’s to add for those.
However, in my research I came across a fascinating but frustrating anomoly – Manufacturers and retailers are inconsistent at best with their room size recommendations, which makes it really hard to figure out what to believe. Take for example this small sample of 10,000 BTU portable air conditioners from several web sites, and compare their wildly differing recommended maximum room sizes:
- Alen C425 (10,000 BTU): 425 s.f. max (manufacturer’s site)
- Amcor AL10000E (10,000 BTU): 300 s.f. max (description on retailer’s site)
- Danby DPAC10031 (10,000 BTU): 450 s.f. max but 250-350 recommended (retailer)
- Royal Sovereign ARP-1000E (10,000 BTU): 400 s.f. max (mfr. site)
- Soleus MAC-10K (10,000 BTU): 400 s.f. max (mfr. site)
- Sunpentown WA1000E (10,000 BTU): 300 s.f. max (mfr. site)
- Whirlpool ACP102PS (10,000 BTU): 450 s.f. max (mfr. site)
I see a range above from 250 to 450 square feet for 10,000 BTU units. That’s a pretty big discrepancy between units of the same documented output. They say to add 20% more BTU’s than you think you’ll need so you won’t find yourself caught short on hot days, but does that mean a 350 square foot room needs 10,000 or 12,000 BTU’s?
I managed to track down some research on BTU vs. recommended room sizes by the Portable AC Guide.com folks that doesn’t appear to be public on their site right now, but was the research that contributed to their recommended BTU vs. room sizes found on their “How to choose the right sized portable air conditioner” page. They mapped 34 models of portable AC units across all BTU sizes and then found some common ground to come up with their own recommended size chart.
Click the thumbnail below to view the full sized chart.