The rising price of electricity in some areas is highlighting new types of hvac equipment that cut the cost of cooling. Among them are dual-drive chillers that can automatically switch, on the fly, between electricity and natural gas. As power prices become more volatile, such equipment could help a customer control his energy costs. It may even allow him to "sell" back part of his electric load to the utility.
When the price of oil was high, customers could switch over to natural gas until the price dropped again. Utilities promoted this option even further through interruptible gas tariffs that offered deep discounts (as high as 40%) for gas if the customer agreed to switch back to oil when called by the utility, typically during very cold spells. Dual-drive chillers could do the same thing for electricity on very hot days.