Solar Self Consumption
Most people who have solar panels intalled on their property tend to be out during the day when the solar is at it's peak. As a result this energy is being fed back to the grid, resulting in the owner of the system having to buy back electricity in the evening and night at normal electricity costs.
Self consumption systems store excess power generated during the day in batteries. This power can them be used when the sun has gone down helping to further reduce the annual electricity bill.
If the owner uses all the stored power the system simply reconnects the to the grid giving a smooth transition.