BTU is the standard measure of cooling power, so the honest way to compare air conditioners is cost per BTU. This ranks every popular window, U-shaped and portable model that way. One catch: portable units are rated on a more generous scale, so filter to a single type to keep the comparison fair, then match the BTU to your room.
Prices reviewed 11 July 2026. AC prices swing with the season and heatwaves, so check the live listing.
| Air conditioner | BTU | Room | Type | Price | $/1000 BTU |
|---|
About 20 BTU per square foot: a 300 sq ft room wants ~6,000 BTU, a 500 sq ft room ~10,000 BTU. Add for sun, kitchens and high ceilings. Do not oversize much, or it cools before removing humidity. Filter by room size.
Window and U-shaped cool more efficiently and quietly per dollar; U-shaped units are very quiet. Portables are easier to install and move but less efficient, noisier, and rated on a more generous BTU scale. Compare within one type.
Portables often quote an older ASHRAE BTU that runs 30-40% above the real-world DOE SACC figure. Window units use a stricter standard, which is why we keep the types separate.
Yes for most. Inverter and dual-inverter units cost a little more but run far more efficiently and quietly, varying compressor speed instead of switching on and off. Over a summer the savings usually justify it.