You aren't "building" anything per se. You're taping flexwatt (that you can buy prewired) to the back of a fridge (or Igloo cooler, whatever), filling some soda bottles with water, and plugging the flexwatt into a thermostat. Or, spend a few hundred dollars to have someone else attach a heating element to an insulated box and have an unreliable thermostat that you should replace with a Herpstat anyway.![]()