It's the new EEG 2027 Amendment which changes things fundamentally. Instead of receiving a flat payout per kwh, installing and connecting a new solar installation from 2027 will be under market condition contracts and depending on the contract has maybe to pay a fee when feeding in during negative price times. The incentive now changed from 'we need to get solar and pay for the electricity' to 'store your electricity and use it yourself'. All existing solar installations before 2027 will continue to receive the flat payout when feeding in the power for 20 years.

It's solar so you can literally just unplug it. Although at the scale of an individual house you can just unplug (or otherwise deactivate) pretty much anything. It's the industrial scale stuff that can't be adjusted on a dime.

Why not store it in small and large battery systems and use it later?