Okay I ran some numbers for you. I don't know what "scv" california is, so I used Fresno, roughly central to CA to figure this.
To save $400/mo or $4,800/year, you'll need between a 25 and 30KW system.
That's... enormous. The array will be larger than your house and require half a room full of inverters and batteries.
I have no idea what it would cost... I'd expect well in to 100,000+. Of course it's my understanding that California provides significant rebates to help offset the costs, and supposedly if you have a big enough system you can even tie into the electrical grid and sell power above what your house needs at any given time back to the electric company for a credit, though PG&E has a track record for being difficult with this, even though they are required by law to do it.
There is a calculator online that you can use to see what various sized systems will save you in electrical costs. Google "PVWatts" to use it. Then you'd have to go and get companies to estimate the cost of the system to you. Generally speaking, even with government subsidies, a solar panel system will return in about 20-40 years on investment, so you need to be really committed.
