It was after this that Tappan saw the solution. Ever since, the system has operated flawlessly and nonstop. During the day, when the cost of electricity is higher due to public demand, the system produces more power than is needed by the dairy. This is sent through a metering system and into the power company's lines. The amount is credited to Arizona Dairy's power bill.
Cost of electricity is lower at night.
This is when the dairy makes its ice and handles other power consuming tasks. In essence, they buy power when it's cheapest and sell it back to the utility when it's more expensive. They did just that. Five years have passed since the first power came from their generator. Despite some earlier problems and the need for design modifications, the entire half million cost, and all interest on the loan, is now paid off.