Use of efficient chillers such as this EarthWise™ CenTraVac from The Trane Company may be a justifiable way to combat global warming in spite of their use of ozone-depleting HCFCs, as the units are designed to keep refrigerant releases below 0.5% per year. This unit achieves very high efficiencies using a multiple-stage compressor with three impellers. Source: The Trane Company