If you have a "smart" electric meter, you may be eligible for special rates, especially if you do your charging during the overnight hours.I have no idea about "tiers." We just have one bill and rate never changes no matter whether we use a little or a lot. Our electric bill for the new house has been pretty good. The old house was drafty as hell and has a POS air conditioner, so bills were super high for 5 months of every year. So far, this house has been pretty good with the electric bill. We'll see how much hubby's charger adds to it.
I'm with San Diego Gas & Electric (even though I'm not even in San Diego County) and I was able to get a different rate tier based upon time of day. The fun part is paying more to have the electricity sent to me ($112) than to generate it ($81).

I can download my hourly power usage and when there's a big difference in power used, that's when the car is most likely charging. Normally, I would charge after midnight, but the wife works third shift so must charge prior to midnight.