Shortest answer: You can't.
Short answer: You don't need to.
Long answer: Because Google PowerMeter and Pulse Energy both require their data to be time stamped with UTC, and because largely the user does not view time-stamped data in the EMU itself, but rather through Google PowerMeter and/or Pulse Energy, and since those companies do the time zone conversion for you, the EMU is 'locked' to UTC.
We looked at giving the option of having the user set a time zone, but it gets really complicated real quick with daylight savings rules, the constant changes to those rules, the fact that there are a few time zones that are only split by 1/2 an hour and so on. It was a lot more expedient for the EMU to be set to UTC and to have it sync with a time server that provides its time as UTC and be done with it.
All that said, three things may change that:
1. We have just released the public interface update for the EMU. This opens wide the doors for people to access their energy data via many other methods than just GPM or PE. While most methods provide local time via their own sources, some will use the EMU time, and so we do recognize that some users might want to see something other than UTC as their time stamps.
2. We have some other cool stuff in store for the EMU which I can't really talk about just yet, but enough to say, we will be revisiting the need to set a local time zone as part of these features.
3. We have had 1 or 2 requests for the EMU to be able to do a time sync with a specified time server. That server may not be set to UTC.
We are looking at this option as well.
Hope that answers your question.
If you want any specifics, just ask and I will do my best to answer.