I haven't researched the overhead costs, but there are alternative kinetic "batteries" that have been proposed, some of which are already being used:

- Use excess energy generation to drive a gravel-filled train up a few miles of 2% grade, back down the track to drive turbine(s) for energy to be tapped

- Run water up an incline into a reservoir. This can simultaneously serve irrigation purposes. Water level is indicative of available energy to be sent through turbines

- Multi-ton flywheels. I've seen that some fusion experiments use this for massive, quick energy bursts. Magnetism prevents excessive wear/tear on bearings