Honeywell HW2CESAWW9

An inverter compressor runs at variable speed, ramping up and down as needed potentially reducing energy consumption.

A remote control for multimedia.

A growing number of air conditioners now have electronic controls. Much like the digital thermostats for heating systems, these can (fairly reliably) hold the room at a certain temperature, shown on a digital display. Many also include a timer feature that allows the user to set an "on" or "off" time--great for, say, having the air conditioner activate automatically to cool a room before you return home from work.

This feature automatically varies fan speed according to differences between room temperature and the thermostat setting. When the difference is wide, the fan runs at higher speed; when the gap is more modest, the fan runs more slowly. The speed will change automatically as needed, to respond to changes in selected setting or room temperature.

This indicator light or flag signals when the filter needs cleaning. It's usually triggered after a certain number of hours of operation have elapsed on the internal clocks in electrical control models. Flag-type indicators can activate in the event that dirt and debris blocks the filter.

The energy-efficiency rating, as supplied by the manufacturer (and as certified by the Association of Home Appliance Manufacturers, AHAM, unless otherwise noted in the Recommendations & Notes). The higher a unit's EER, the lower its operating cost compared with other models of its size.

The combined energy-efficiency rating, as supplied by the manufacturer (and as certified by the Association of Home Appliance Manufacturers, AHAM, unless otherwise noted in the Recommendations & Notes) which calculates the model's efficiency when combining operation in cooling and standby modes. The higher a unit's CEER, the lower its operating cost compared with other models of its size.

The unit's cooling capacity, as supplied by the manufacturer (and as certified by the Association of Home Appliance Manufacturers, AHAM, unless otherwise noted in the Recommendations & Notes). Capacities range from 5,000 British thermal units per hour (enough for a modest-sized bedroom) up to 12,500 Btu/hr. (adequate for a large, sun-drenched room or even two interconnected rooms).

In general, smaller-capacity models are lighter, while larger-capacity and some high-efficiency models tend to be heavier.