10kWh during periods where the energy market price is at the lowest will not pay for 5kWh for periods where the price is at the highest. It will be closer to 0.1-1 kWh for every 10 kWh.
The alternative (the current model where I live) is to have the government be responsible for grid stability, in which they will add taxes and fixed grid connection fees to pay for that service. Crediting overproduction won't make the costs lower for the government, so any such credits will just be a form of subsidy.
I'm happy to sell my solar power at night.
A couple buffer batteries in each home should eventually help even out pricing with everyone trying to sell during peak demand times. But yeah, grid stability might be a fun challenge.