You do realize that batteries are not the only method of energy storage? In fact, there are lots of better ways to store excess energy from renewables over longer periods of time, but power to gas was mentioned as an example that works everywhere, and can use abundant existing storage and distribution systems.

Lets add a reference to get some actual numbers to play with: The US Energy Information Administration has published a report reasoning about the levelized cost of electricity (LCOS) for new power plants of different energy sources [1]. According to page 8 of this report, the LCOS of one megawatt hour of nuclear energy is around 69 USD, while solar is around 33 USD and onshore wind is 37 USD.

If you factor in a 50% loss in converting the renewable energy to gas and back to electricity you end up in the same ball park as nuclear, but without the proliferation, safety, and waste problems.

[1] https://www.eia.gov/outlooks/aeo/pdf/electricity_generation....