In certain embodiments, a thermoelectric heat pump includes a heat transfer region having an array of thermoelectric modules, a waste channel in substantial thermal communication with a high temperature portion of the heat transfer region, and a main channel in substantial thermal communication with a low temperature portion of the heat transfer region. An enclosure wall provides a barrier between fluid in the waste channel and fluid in the main channel throughout the interior of the thermoelectric heat pump. In some embodiments, the waste fluid channel and the main fluid channel are positioned and shaped such that differences in temperature between fluids disposed near opposite sides of the enclosure wall are substantially decreased or minimized at corresponding positions along the channels.