Have you talked to your landlord about adding solar panels to the roof? He/she could install them and connect them to your apartment's service, which means you would get the power and the savings -- though you might reasonably expect some of the savings to go towards higher rents in the future. With the tax advantages, it's almost a no-brainer.
It's even possible to apportion power between multiple units with PG&E in California. They even allow "neighborhood solar", where you can benefit from a larger system installed elsewhere, like over a parking lot.
I would also +1 the other comments about thinking really hard about whether your system is safe in the event of high winds. Solar panels are basically large sails, you'd be surprised what a 50 or 60 mph wind gust (likely to happen once or twice a year) can do. If you plan on doing this, check your lease - many landlords forbid putting things on the roof or hanging outside windows, or running wires on the exterior of the building.