Solar energy-produced electricity is poised to grow exponentially as solar panels get cheaper to install, more efficient batteries are developed to store the sun’s energy and investors pour more money into an increasingly reliable energy source.

Energy produced by the sun is already providing electricity to about 30 percent of the United States, and investors have taken notice of the investment potential. Big banks, pension funds and insurance companies are seeing opportunity in the $15 billion industry that provides stable returns and isn’t dependent on overall market conditions for its continued growth.

“They write bigger and bigger checks,” said Jesse Grossman, chairman and CEO of New Jersey-based Soltage, which develops and operates large solar farms for hospitals, municipalities, commercial and industrial clients in 15 states. Grossman made his comments at a recent panel discussion on electricity hosted by the University of Houston.

Read more: Solar energy now mainstream power source