Solar power now provides roughly 1% of the world’s electricity. It took 40 years to reach that milestone. But, as they say in tech, the first 1% is the hardest. You can see why in this chart below.

As solar prices drop, installation rate rises. As the installation rate rises, the price continues to drop due to the learning curve.

How fast is the acceleration?

Looking at the projections from GTM, it will take 3 more years to get the second 1%.

Then less than 2 years to get the third 1%.

And by 2020, solar will be providing almost 4% of global electricity.

GTM expects that by 2020, the world will be installing 135 GW of solar every year, and will have reached a cumulative total of nearly 700 GW of solar, roughly four times the 185 GW installed today.

For context, at the end of 2013, after almost 40 years of effort, the world had a total of 138 GW of solar deployed. We’ll deploy almost that much in a single year in 2020. And the numbers will keep on rising.

The growth of the total amount of solar deployed around the world continues to look exponential, with a growth rate over the last 23 years of 38% per year. Over the last three years it’s slowed to a mere 22% per year. All exponentials become S-curves in the long run. But for now, growth remains rapid, and may indeed accelerate once more as solar prices drop below those of fossil fuel generation and as energy storage plunges in price.

The first 1% was the hardest.

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There’s more about the exponential pace of innovation in solar, storage, and other technologies in my book on innovating to beat climate change and continue economic growth:The Infinite Resource: The Power of Ideas on a Finite Planet