It’s exponential.

livemint.com/…/the-exponential-growth-of-solar-po…

To call solar power’s rise exponential is not hyperbole, but a statement of fact. Installed solar capacity doubles roughly every three years, and so grows ten-fold each decade. Such sustained growth is seldom seen in anything that matters. That makes it hard for people to get their heads round what is going on. When it was a tenth of its current size ten years ago, solar power was still seen as marginal even by experts who knew how fast it had grown. The next ten-fold increase will be equivalent to multiplying the world’s entire fleet of nuclear reactors by eight in less than the time it typically takes to build just a single one of them.