Usually people power peltier units using PSUs which can get expensive with the more units you have. For those of you looking to build a TEC cooler with a lower cost, here are some options: Corsair CX430 can be bought on sale for ~$15-20 and provides an upgrade path for larger Pelts since it has a larger amperage and a fan. One of the best choices without breaking the bank Original Xbox 360 power cables (175 watt) can be used to provide 12 volts at ~4.2 amps per unit. Since they can power three units per plug they are an option. However sinve there is no fan positioning is key since they get warm. Should only be considered if you already have one and only a few TECs.