Batteries are good for N cycles (to simplify) and take M carbon to produce. If it cycles N times and is charged with fuel that emits <M carbon, that’s going to

Batteries are good for N cycles (to simplify) and take M carbon to produce. If it cycles N times and is charged with fuel that emits <M carbon, that’s going to be a net carbon output surplus. This is expected and desired from solar to have some carbon output as a tradeoff to supply bursts of demand, but needs to be compared with eg a comparable coal plant (or “wood pellet” plant I guess) in order to figure out how much improvement it gives.