Although I am an advocate of the use of PV, particularly with the government and utility incentives that may be available, the "sustainability" is in doubt. Why? Because although PV panels reduce electrical energy produced by coal, they're not very efficient (about 15% conversion).
Generally, an array that can fit on half a garage (about 4 kW) will produce enough electrical energy for the average house, and warranties are about 25 years. Nobody's owned the current PV products for 25 years so they might last longer, say 40 years, but who knows if performance deteriorates over time.
Regardless, the continued gains in efficiencies and reductions in manufacturing cost will make current PV panels obsolete in 5 to 10 years. When the current PV panels are replaced, where will they go? As a monstrous hybrid (difficult if not impossible to recycle into their original materials), they can only be reused (donated to low-income economies) or trashed. So it all depends on whether your definition of "sustainable" includes just today, or tomorrow.