In some situations it's possible to imagine closed loop systems that produce CH4 from excess power and use it as storage instead of batteries
I suspect you are aware of the grid scale experiment that informed my comment (Falkenhagen): I used to work for the company concerned. Technically it works a treat, as long as you don't mind the losses.
The system problem is that while the excess power from renewables is sufficient to drive wholesale prices briefly negative, the actual volume of energy concerned that we might regard as excess is pitiful compared to aggregate demand. So "power-to-gas" becomes an expensive way of storing fairly small amounts of energy. I can see that it could work (and may have to work) for high value applications like synthetic aviation fuels, but keeping people's Xboxes and TVs running, I really don't see that being commercially viable.