Good Morning,

I live in the Chula Vista, CA area. (San Diego). I built a granny flat. I have a 400AMP underground service from the street to a 2 meter base on my existing home. 200 AMPS for the front house on one meter, and 200 AMPS for the rear house on another meter. There are two, 200AMP breakers on the meter base box to feed the panels to each home.

The panel for the second home is located 121 feet from the meter base and is connected with two inch PVC electrical conduit underground. This should give you enough information to answer the question, which is:

What type and size of wire do I need to connect the meter base to the breaker panel in the second/rear home? I have reviewed several similar questions and there does not seem to be a definitive answer. I'm hoping I can use aluminum, because I priced the cost of 3/0 copper and almost fell over ! I did note when the power company connected their lines to the meter base, they used aluminum wire.

Thank you very much.

You can use 4/0 (hot) 4/0 (hot) 2/0 (Neutral) Aluminum USE-2/RHH/RHW-2.
You will also be required to run a #6 bare copper conductor in the same conduit per 2008 NEC. Yet, if your jurisdiction is not enforcing the 2008, I would run it any way. I'm not going to get into the requirements on should I or shouldn't I run an EGC. It's best to just run one!

Note: Some jurisdictions require you to run four conductors to remote structures requiring power, and some do not. It is best to check with your authority having jurisdiction on this requirement. But, if it was me, I would run it!

Hope this helps!