I don't know a ton about them as far as trouble shooting. All I know is I have a hybrid one, meaning that it has electric coils to heat up the water small amounts during the day, and then overall is heated in large amounts by my oil fed furnace.
So when the thing sits around all day being unused, the coils heat it up and keep it the right temperature range, but when I take a shower or use hot water, (and the tank is evacuated a bit, and new cold water comes in) it is heated by oil.
I doubt you have oil fed furnaces out in Cali, but a hybrid set up, using natural gas is probably the most efficient set up. Oh, and make sure you insulate the tank very well with a good wrap.