Here is an interesting idea: a solar billboard that generates 3.4Kw of electricity during the day (that’s in peak conditions, I guess) and sends it back to the grid. At night, it does consume electricity, also from the grid, to light itself. However, it produces more energy than it uses hence the “this isn’t a billboard. It’s a power plant” tag line.
At this point, this is just a demo, and we don’t know if billboard will massively become solar. If 3.4Kw doesn’t ring a bell, PG&E says that it’s enough to power a family of four for one day. Via Live Science