They've already bought a large battery - bolted under their electric car. Perhaps one day our cars will drive us into work, we'll plug into the grid there (or have it drive itself home), and home solar will talk to the grid and tell it how much to,charge our car during the day. Then we'll go home and run our house off the car battery overnight, making sure to leave enough battery power to get to work the next morning. Or party on Friday night because it was sunny and we have a couple dozen extra kilowatts that don't need to be saved for commuting in the morning!