Described here are systems for regulating the temperature of a heating or cooling device without adjusting the input power. In general, the systems described here comprise a heating or cooling device and a controller. The heating or cooling device typically comprises a cold region and a hot region, there being a temperature difference between the two, and an input power. The controllers are configured to be placed in thermal contact with at least a portion of the cold region and at least a portion of the hot region, and are configured to create a path for heat exchange between the portions of the contacted hot and cold regions. The heat exchanged may be controlled and the temperature of the system may be user adjustable, or it may be automatically controlled.