Absorption chillers use heat to generate chilled water for cooling. If the source of heat is inexpensive or even “free”, such as recovered waste heat from a biogas-fueled engine-generator set, absorption chillers can cost significantly less to operate and maintain than conventional electric compression chillers. The fact sheet gives an overview of the two types of absorption chillers, lithium bromide/water and water/ammonia, and describes the basic process, components, designs, and comparison with conventional chillers.