More than 500,000 people visit the resort every year, so with towels and linens to wash, and attractions to heat, much of that hot water now can be heated from the rooftop.
Don Wichert of Focus on Energy said he hopes other large resorts take notice. "We think there's a huge opportunity in Wisconsin, and in other places to use it, especially for places like the Kalahari, that use a consistent amount of hot water every day."