Research shows that the running cost for a solar-powered arrangement will reduce with the consumption going up. That means that your ROI is even more impressive as your requirement for solar-powered units increase.
Unlike houses that have a roof structure of smaller dimensions and often not at the same level, roofs of factories are (a) Very expansive and (b) Flat from end to end. And that means that the company can install solar panels for long stretches. Thus, creating a large bank of unhindered, unobstructed rows and columns of solar panels.
Tesla has its own largest factory, Gigafactory that depends on solar power for its operations. Likewise, Apple runs its largest data centre on energy from the sun (a 200MW unit). There are several other companies that are moving to solar energy for their plants.
It is time architects and energy experts across the globe take this energy source seriously and recommend their clients to go solar now. Manufacturers will not say no because they care for the bottom line.