Heat transfer compositions are usable in their own right or are suitable as a replacement for existing refrigeration usages. The compositions possess a reduced Greenhouse Warming Potential, yet have a capacity and energy efficiency (which may be conveniently expressed as the “Coefficient of Performance”) ideally within 20% of the values of those attained using R-134a, and preferably within 10% or less (e.g. about 5%) of these values.