During the six-month period (January – June), renewables surpassed nuclear power in three of those months (March, April, and May) while nuclear power took the lead in the other three. In total, according to EIA’s data, utility-scale renewables plus small-scale solar PV provided 20.05% of U.S. net electrical generation compared to 20.07% for nuclear power. However, renewables may actually hold a small lead because while EIA estimates the contribution from distributed PV, it does not include electrical generation by distributed wind, micro-hydro, or small-scale biomass.
EIA has acknowledged the neck-in-neck status of nuclear power and renewables and stated as much in a news release it issued in early summer. However, the agency simultaneously stressed its view that “nuclear will generate more electricity than renewables for all of 2017.” 
Well, maybe …. maybe not.
While renewables and nuclear are each likely to continue to provide roughly one-fifth of the nation’s electricity generation in the near-term, the trend line clearly favors a rapidly expanding market share by renewables compared to a stagnating, if not declining, one for nuclear power. Electrical output by renewables during the first half of 2017 was 16.34% higher than for the same period in 2016 whereas nuclear output dropped by 3.27%. In the month of June alone, electrical generation by renewable sources was 27.15% greater than a year earlier whereas nuclear output dipped by 0.24%.
In fact, almost all renewable energy sources are experiencing strong growth rates. Comparing the first six months of 2017 to the same period in 2016, utility-scale + small-scale solar has grown by 45.1%, hydropower by 16.1%, wind by 15.6%, and geothermal by 3.2%. Biomass (inc. wood and wood-derived fuels) has remained essentially unchanged – slipping by 0.8%. Electrical generation by solar alone is now greater than that provided individually by biomass, geothermal, and oil (i.e., petroleum liquids + petroleum coke).
And on the capacity front, renewables long ago eclipsed nuclear power. For the first half of 2017, the Federal Energy Regulatory Commissions recently reported that renewables’ share of total U.S. available installed generating capacity is 19.70% compared to 8.98% for nuclear — i.e., more than double. 
“Nuclear power is in irreversible decline in the U.S., due to rising costs and failing economics of new and existing reactors, alike,” said Tim Judson, executive director of the Nuclear Information and Resource Service. “Last month’s cancellation of half the new reactors under construction in the U.S. means that gap is going to be wider than projected, and accelerating.”