Yet hidden above the glowing Eiffel Tower, neon resort awnings and a black pyramid that shines a beam of light into space, is one of the largest rooftop solar arrays in the country.

Twenty acres of sun-catching glass sit atop the Mandalay Bay convention center, and when new installations are complete, it will become the biggest rooftop solar array in the US.

In recent months, three of Nevada's largest casino companies—MGM Resorts, Wynn, and Las Vegas Sands—have announced plans to buy and produce more renewable energy for their hotels, a move driven both by increasing demand for responsible energy use from the companies that rent their conference halls, and a surplus of cheap power from solar farms in Nevada and California.