The typical central air-conditioning system of the early 1990s had a SEER of about 6. This model operates at low speed about 80 percent of the time, and shifts into high gear only when necessary. But experts say Trane tends to be more expensive than Carrier for comparable quality levels, and the company has been slower to begin the transition to the newer, more environmentally friendly refrigerant that manufacturers will be required to use by 2010. For these reasons, the TTZ is not included in ConsumerSearch Fast Answers. The rationale is that the newest designs are relatively unproven, and their more complicated two-speed compressors may require more repairs.
Midrange units are significantly less expensive as well.
This unit's warranty, including 10 years on the compressor and coils and 5 years on all other parts, is the best we've seen, and experts say it's quiet and efficient at its single speed. Budget models will get you a SEER of about 10 and less sound insulation. But you should still expect a sturdily built unit with a decent warranty. Cooling load is computed based on the size of your house, the climate in your area, and other factors such as shade, glass area and ventilation. If your air conditioner is undersized, it won't cool effectively.