Solar energy has sex appeal. If you want to show the world you're doing something to reduce pollution, you put photovoltaic(PV) Generation of electricity directly from sunlight. A photovoltaic cell has no moving parts; electrons are energized by sunlight and result in current flow. (PVPhotovoltaics. Generation of electricity directly from sunlight. A photovoltaic (PV) cell has no moving parts; electrons are energized by sunlight and result in current flow.) panels on your roof to generate clean electricity. Even better, you drive a plug-in hybrid or an all-electric car and charge your car's batteries with your clean solar electricity.
The good news for solar enthusiasts is the cost of installing a solar electric system on your home just keeps falling and falling. Let's take a look at some data and then ask if it’s time to abandon energy efficiency.
from Building Science http://www.greenbuildingadvisor.com/articles/dept/building-science/does-cheaper-solar-mean-we-can-forget-efficiency