Decentralized solar generation helps the grid in some ways but hurts it in others, specifically the need for sundown peak generation. See for example the "duck curve" problem that CAISO is facing: https://www.caiso.com/Documents/FlexibleResourcesHelpRenewab...
Only if you don't have batteries at home. Tesla promotes buying the roof with a battery pack which would allow you to use evening energy by battery and charge overnight (good for the grid) for the morning peak.
