Let’s start off with what these are. LowE2 is 2 thin coats of silver oxide on one of the surfaces of you dual paned glass so it is reasonable to assume that LowE3’s 3 coats are even better as the reduce heat flowing out of your home (measured by U-Factor) or the sun heating your home up from the outside (SHGC). On a cool winter day in San Francisco, a bit of sunlight heating up your floor is a good thing (besides your dog/cat will thank you for it) and 2 coats allow more sun in. There is a reason why the state only requires you to have LowE2 in coastal cities. In this case, the government is right. Another item to consider is that LowE3 has a darker tint to it which some people don’t like on their homes as it looks industrial. If you live in San Jose, Pleasanton or father into the east bay, you don’t have a choice and need LowE3.
Call for a in-home visit and ask as we know the code better than most.