These guys have two projects (check their operating plants) using flywheels. They're used for frequency regulation. About 20MW each.
Or do you plan to focus more on microgrids?
We're still working out costing, but it might even make sense for residential use to take advantage of time-of-use rates or energy arbitrage. Other applications are industrial processes that require high power for short periods.
Hopefully constructive feedback: I would put that residential thing further down on your list. I think that stuff tends to be too complicated unless / until you can aggregate a lot of loads (eg. I think Tesla only recently recently started doing this stuff residentially. Probably awhile before you reach their scale...)
