To actually run your car on sunshine, you'd need a battery system at home. But battery charging losses are greater than the local electrical grid. So it's most practical to use the electricity from the panels at the time of generation and nearby.
Here in Sacramento, SMUD, the local utility, has a "solar shares" program, where you buy into a solar farm nearby. It costs a little more year round, but it evens out your bills all year. You get credits for "your" solar panel generation, and you get to increase demand for solar, there are no installation costs, and no maintenance.
I think utilities are reluctant to give you time-based billing when you have solar in place. They don't want to pay you peak- or ultra-peak-rates for your solar power.
It's what I'll be putting on the roof of my Round The World 4x4.
Possible solutions:
1. Buy an extra Tesla battery and swap the batteries in the evening when you get home from work. I know this isn't presently practical [EDIT: at home without special equipment], but the idea of swapping electric car batteries is being discussed for the future, to avoid long charging times.
2. Buy an exotic and very efficient home battery bank to store the daylight solar energy until it can be delivered (as charging current) to the Tesla after dark.
3. Shame your employer into installing a solar changing station at your place of work. Emphasize the terrific public relations advantage, don't mention the cost.
Your suggestion of feeding the grid is by far the most practical approach, because it's already an option in many places.
It may not be practical to do at home but Tesla has already demonstrated automatic battery swapping on their Model S. They've timed it at twice as fast as filling up a comparable luxury gas car:
California appears to be phasing out that requirement (ability to swap the pack), which is why battery swap stations are no longer being pursued aggressively.
http://articles.latimes.com/2013/may/05/business/la-fi-elect...
http://gas2.org/2014/07/02/ev-battery-swap-stations-may-be-a...
It had to be planned. I don't think it was feasible in the roadster because of the battery placement. But the model S has a nice flat battery on the bottom of the car, making for great weight distribution and easy access. I haven't seen any news of any actual swap stations though.
Also, I don't think that battery lifetimes can be stated with such certainty yet. Few electric cars have been running long enough to know just how the batteries age with that usage. About the closest available is the fleet of older Priuses that are hitting a decade or more on the road, and they seem to have occasional failures but not the consistent aging that's been predicted... but of course they use the battery completely differently, and capacity is less important.
However, during an unproductive daydream session, I realized that my solar panels would produce electricity during the exact hours that my car would be parked at work. In fact, during peak solar hours, my house uses very little energy at all.
Reverse meter billing would perhaps net out the cost of energy used at night with the energy produced during the day -- but I'm fairly certain by the time I get around to doing all this our utility will have implemented demand-based pricing on electricity, making it fairly cheap to charge your car at night.