A photovoltaic system converts light  into useable electricity for your home. Modern PV systems are very reliable, cost about $8000-$12000 per kilowatt installed (before incentives), require about 100 sq ft of unobstructed area per kilowatt, and weigh 4-6 lb per sq ft (for mono  and multi-crystalline panels).

A typical household uses 10,000 kilowatt hours (kWh) of energy each year. A 3 kilowatt PV system in Western Oregon will produce about 3000 kWh during the year, or about 30% of the annual household energy. In Eastern Oregon, the same system would generate about 4000 kWh, or about 40% of the annual energy.

Energy payback of PV:

How long does it take a photovoltaic system to generate the energy that was used to manufacture it?  NREL says 1-4 years.  Read the report.