Solar has two issues:
1. It doesn't handle high inrush currents very well, for example when a large industrial motor is turned on. However, it's great for things devices that draw relatively constant power (televisions, computers, lights, charging electric automobiles, refrigerators, etc).
2. There's currently no economically viable way to store solar energy. Batteries are too expensive and have a short lifespan.
Both of these can be solved with advancements in flywheel technology. Here's a link to Beacon Power's site. This company makes industrial flywheels. I won't go into the technological details, so I'll just say that flywheels convert electrical energy into kinetic energy and vice versa, and they can do so at around 98% efficiency. NASA has been using them for years. The problem is that they're really expensive right now, mostly because there's not much of a demand. But once the general public has its hands on solar energy that's cheaper than coal, the demand for energy storage is going to go through the roof. Flywheels are theoretically capable of handling high inrush currents, as well, but that's more difficult to engineer than simple energy storage.
Here's a decent Scientific American article on solar cell cost trends: