The BIGGEST problem with clean energy

In my mind, individual houses could use advanced Flywheels to store energy during non-peak hours & use both solar & wind energy to spin the flywheel up using highly efficient electric motors/generators when excess energy is being generated & put surplus energy into the grid when the flywheel(s) is/are at capacity.

The costs of such a solution aren't currently viable for most homeowners though, but *flywheels can last decades* without losing efficiency & advanced options are already on the market. They also don't represent a fire hazard like molten salt solutions.