Temperature control systems and methods can be designed for controlling the interior climate of a vehicle or other the climate of another desired region. The temperature control system for a vehicle can have a thermoelectric system providing heating and/or cooling, including supplemental heating and/or cooling. The thermoelectric system can transfer thermal energy between a working fluid, such as liquid coolant, and comfort air upon application of electric current of a selected polarity. The thermoelectric system can supplement or replace the heat provided from an internal combustion engine or other primary heat source. The thermoelectric system can also supplement or replace cold energy provided from a compressor-based refrigeration system or other primary cold energy source.