Another factor seldom considered by idealists is the space requirements for alternative energy. If you covered the roof of a Walmart with photovoltaics it would not produce enough energy to supply all the needs of the store. A couple weeks ago I read calculations of the space required to provide solar electricity to NYC. The state of Connecticut would have to be covered with solar panels just for NYC (skyscrapers have limited roof space and high occupancy/energy demand).
Also having worked around my own system, solar panels only utilize about 15% of the energy the sun provides. The remaining 85% produces high temperatures on the panels that will literally burn the piss out of you when you bump into a panel. Excess heat is also destructive to the components, one contributor to the short lifespan of a panel. Some manufacturers are saying they have a 40 year lifespan, but that is only based on accelerated testing, not real world proof. Other data suggests they may have it up to 30 years, but the biggest problem remains, they lose efficiency over time just as a matter of the physics that produces the electricity. Like I said, technology will drive improvements.