Legal Question in Consumer Law in California

I am sure the solar company used the number of $1100 as an estimate. You will be hard pressed to find any guarantee in the sales agreement. They are too smart for that.

Be glad you are helping to save the earth.

You may or may not. That is not the kind of question that can be answered based on a summary like that. You would need to sit down with an attorney and go over the details. As Mr. Marman says, if the company covered themselves by couching the figure in terms of a "guestimate" or "customer average," etc., you have no case. If they actually told you as a fact that you would save that much, then you may have a case. For it to be fraud, or negligent misrepresentation, however, they would not only have presented it as a true statement of fact, but they must have known it was not true, or had no reasonable basis for believing it was true. Otherwise it's just a breach of express or implied warranty. The other thing you have to consider is $680/yr (the difference between $1100 and $420) times the life of the system adds up to what? MAYBE $13,000 if the system has a rated life of 20 years (I bet it's less). Pretty hard to mount a court case to recover such a small amount.