Refrigerator economizer:

If your refrigerator is still one of the old types with an ‘automatic defrost’ system, this economizer can help you reduce your electricity billls. These old models are provided with a small heating element to prevent icing up, but in general this is at best inefficient and adds unnecessary kilowatt-hours. The circuit described in this article limits the number of defrost cycles in such a way that your electricity bills are reduced without an increase in ice formation.