A violation of PC 118 or perjury is difficult to prove under CA state law. Note subsection (b) which provides that "No person shall be convicted of perjury where proof of falsity rests solely upon contradiction by testimony of a single person other than the defendant. Proof of falsity may be established by direct or indirect evidence."
Beyond that the falsity must be willing and knowing. Probably for these reasons you don't see many perjury prosecutions.
To answer your question about the penalty of perjury under California law, I will use welfare fraud as an example. Perjury prosecutions are actually pretty common in welfare fraud cases.
Most welfare documents are signed under penalty of perjury. In many counties in California, including in San Bernardino, when a person makes false reports about their income, living situation or other facts that determine the amount of government aid, the District Attorney will file one of two charges:
Penal Code 118(a), perjury, which is a felony punishable by 2, 3 or 4 years in prison.
Welfare & Institutions Code 10980(a), obtaining government aid by false statements. This is a "wobbler," which means it can be charged as a felony or a misdemeanor. As a felony, it has a maximum prison sentence of three years; for a misdemeanor, you can get up to a year in jail.
In these cases, the DA will usually agree to dismiss the perjury charge if the defendant pleads guilty to welfare fraud. The defendant is then placed on felony probation, usually with some jail time, and an agreement the felony conviction will be reduced to a misdemeanor when the defendant pays back any welfare overpayments.