Verizon, the biggest wireless provider in the U.S., is doubling its investment in on-site solar.

Yesterday, the company said it would support another $40 million of solar PV projects developed by SunPower at facilities in five states, adding to the $140 million it has invested in renewables over the last two years.

With 25 megawatts of projects now completed or in the pipeline, Verizon will soon become the leading producer of solar among all telecommunications companies in the U.S.

Why is the company doing it? James Gowen, Verizon's chief sustainability officer, said it's all about "driving shareholder value" by investing in a technology that is providing reliable savings. Gowen also said it's part of a bigger resiliency strategy that includes installing on-site fuel cells and intelligently managing energy use within corporate buildings.

The days when corporations bought renewable energy credits in order to look "green" seem to be over. Many of the biggest corporations, such as Apple, Google, Microsoft, Ikea, Wal-Mart and Verizon are contracting for thousands of megawatts of renewable electricity to power their operations, while also installing record amounts of solar PV directly at facilities.

Verizon's Gowen told Bloomberg TV in an interview that solar is "delivering value for us all year long."

"It’s not just about going green. It’s about driving shareholder value; it’s about building redundancy," he said. "Green energy -- regardless of your industry, regardless of what’s going on -- it’s good for all."

Watch the Bloomberg interview: