A Peltier is a heat pump, When electricity is pumped trough it, one side get's very cold, while the other side get's very hot. They due this at a expense though, they not only pull away heat from the cold side, and move it to the hot side, but also add in additional heat of their own. Meaning they are not very effecient. A 60 watt peltier may only pull 40-watts of heat away from the cold side, but add in 20 watts of their own to the hot side. In order to work more effecient you have to pull the heat away from the hot side, by using air, or even better- water cooling. Peltier in watercooling systems can often get well below zero degree's on their cold side.