Frigidaire FRA156MT1 (15,100 BTU)

Most window air conditioners are meant to cool a single room. But if you have an open floor plan, vaulted ceilings or a one-room building like a shop, the 15,100-BTU Frigidaire FRA156MT1 is designed to cool 900 square feet. Owners are overwhelmingly satisfied with its performance, and several appreciate that it runs on a regular 120-volt outlet so they don't have to install a special circuit. The unit is Energy Star-rated and includes the usual features of all but the most basic air conditioners -- remote control, three-speed fan, 24-hour timer, sleep mode that gradually raises the room temperature to save energy and automatic restart after a power outage. It also alerts you when it's time to clean the antibacterial filter.

However, this big AC might not fit in all windows; it's more than 23 inches wide and almost 18 inches tall, and weighs 100 pounds. It does have a slide-in chassis, however, so you install a lightweight sleeve first and then slide the heavy unit in. It can also be installed through the wall. Some owners say the FRA156MT1 is quiet, but others find it loud and don't recommend putting it in a bedroom or TV room. Overall, this big, heavy, pricey unit would be overkill in most rooms. If you don't need quite as much cooling power, the 12,000-BTU LG LW1212ER (*Est. $320) costs much less and is appropriate for spaces of about 550 square feet.

Most of the user feedback for this air conditioner comes from Lowes.com, which sells the Lowe's-exclusive but essentially identical LRA157MT1 (*Est. $400). Other sites with owner reviews include Walmart.com, Amazon.com and Overstock.com. We spotted no professional evaluations.