US solar output up 47% in '17

In the year to September, the electricity generated from solar panels was 47% more than the same period of the previous year.  New investment in solar was prolly pushed up by the likelihood of a big rise in tariffs on imported panels next year.

It's tempting to say, "so what?", because solar produced just 1.9% of total electricity generated in that period.  But consider.   Let's suppose the rate at which the percentage of solar rises as new solar farms are built is just 23% per annum rather than 47%, slowing next year (see chart) because the prices of solar panels go up after tariffs are imposed.   This takes the percentage from solar to 5.5% by 2022, which is what   GreenTech Media and SEIA (Solar Energy Industries Association) forecast.

Source: GTM/SEIA
Note: the left axis shows new capacity not cumulative capacity

 Assuming that growth rate continues--and it might accelerate, because the cost of solar will resume its falls after next year's increase, and meanwhile, storage will more than halve its cost over just the next 5 years--that implies 15.5% of all electricity generated will be from solar  by 2027, and 44% by 2032.  In practice I think solar will be a bigger part of electricity generated by then because its cost will have declined so much it will easily edge out gas and what is left of coal.  But even 44% implies that soon after, more than 50% of the USA's electricity will come from solar.   Since wind will also be growing, though more slowly, its current 5.6% will have risen to 20% or more, and hydropower will be 5 or 6%, its current level.  By 2040, easily 100% of US electricity generation will be from renewables.