Californian governor Jerry Brown has signed into law a bill that will require the state to acquire all its electricity from zero-carbon sources by 2045. While the news is being reported as a push to 100% renewables power generation, the website Quartz has highlighted the nuance of the wording of the bill. By stating ‘zero-carbon’, the bill leaves open the possibility of the use of nuclear power and carbon capture and storage equipped conventional power generation. As Quartz explains, this appears a pragmatic choice, as a recent study estimated that to run the US grid on 80% renewables with lithium-ion battery storage as a backup would mean US$2.5 trillion dollars (€2.15 trillion) of expenditure on batteries at present prices, and around four times more in the case of 100% renewables. (The study, described in an MIT Technology Review post, mentions how the Californian situation is particularly acute.) Battery storage prices will fall in the coming years, and there may also be a shift, as Germany foresees, to higher use of electricity when the sun is shining and/or the wind blowing, and lower use otherwise, but nevertheless the “zero carbon” wording may prove highly important to the state in meeting its goal.