With energy-consuming equipment, such as water heaters and refrigerators, we have good data on energy consumption and can set clear standards accordingly. In some product categories—clothes washers, for example—Energy Star standards were adopted because those standards provide a high enough threshold to represent just the very top segment of the product market (less than 10%). In other product categories—e.g., refrigerators and dishwashers—we set a higher threshold than ENERGY STAR: for example, exceeding those standards by 10% or 20%. With lighting and lighting control equipment, certain generic products qualify, such as compact fluorescent lamps and occupancy/daylighting controls, while in other categories only a subset of products qualify. In some cases, products that meet the energy efficiency requirements are excluded, because of evidence of poor performance or durability. Microturbines are included here because of the potential for cogeneration (combined heat and power) that they offer.
Platinum XM and ZM
American Standard (the parent company of Trane) offers the Platinum XM and ZM air conditioners with variable-speed fans and Dual Duration™ compressors that provide two-stage cooling: a smaller compressor handles most of the work, but on the hottest days a larger compressor takes over. With SEER rating of up to 18 and 20 respectively, these are among the highest-efficiency central air conditioners available. They are available from 2 to 5 tons, and have a ten-year warranty. These units use R-410 refrigerant.
The two most important issues with compressor-based cooling systems are energy efficiency and potential ozone depletion from refrigerants. Most unitary equipment now uses R-22, an HCFC, as the refrigerant. This refrigerant is slated for phaseout by 2020. A few units use HFC refrigerants, which do not affect the ozone layer but are greenhouse gases that contribute to global warming if released to the atmosphere.
Seasonal energy efficiency ratio (SEER) ratings compare cooling capacity (in Btu) to energy inputs (in watts) and are helpful in evaluating central air-conditioner performance. One ton of cooling capacity represents the ability to remove 12,000 Btu of heat per hour.
Also consider the moisture-removal capability of air-conditioning equipment.
Ratings and Commentary