Roof requirements: You need as little as 50 square feet for a starter system and as much as 500 to 1,000 square feet for one capable of meeting all a home's energy needs. A square foot of single or poly-crystalline silicon module area produces 10 watts of power in bright sunshine. So a 1,000-watt system needs 100 to 200 square feet of roof.
Composition shingle roofs are the easiest to work with; slate the most difficult. Shake roofs, flat concrete tile and mission tile roofs fall in between.
Importance of sun: Shade is a killer and cloudy days cut efficiency to 10% of full output. A south-facing roof is best.
State law says your neighbor's tree can't block the sun from getting to your solar panels.
Cost factors: Costs vary wildly due to differences in energy consumption. $8,000 a kilowatt of solar capacity is a good benchmark. So a 2-kilowatt system would cost about $16,000.
The state Energy Commission manages an $84-million fund (paid for by utility ratepayers) that covers up to half the costs of a solar system. Contact the energy call center, (800) 555-7794. Los Angeles Department of Water and Power customers aren't eligible but the DWP has a similar program. Call the department at (800) GREEN-LA.
Finding a solar provider: The Energy Commission and the California Solar Energy Assn. (http://www.calseia.org) provide lists. Ask questions and go with a company that has experience.
Getting connected: Contact your utility for an interconnection agreement and a purchase and sales agreement so you can trade solar power for utility power when you need it.
(Sources: California Energy Commission and Don Loweburg, Offline Independent Energy Systems.)