Sub-metering lets an EV charger be metered separately from a house, theoretically allowing it to take advantage of lower EV rates during more restricted times.
1. https://www.utilitydive.com/news/california-puc-ev-electric-...
It wouldn't make much business sense for the utility to lower your rates when you are charging your car. It's usually the other way around: you charge your car when the utility rates are lower. Which utility is this? Also how are they detecting a car charging vs some other large load like an AC or electric stove?
I'm not sure if it comes from state funding, or profit, but they want to incentivize charging at off peak hours.
https://www.sdge.com/residential/pricing-plans/about-our-pri...
I'm not sure how they detect it, but it's reliable. My naive assumption is that they detect the sustained 7kW increase, in the wee-hours. I haven't attempted to trick it.
This is doubly true in California, where almost no utility will sell you power at low rates during peak demand hours.
As it is, our time-of-use plans are hardly any cheaper off-peak vs on-peak. They've made my plans worse and worse over the years.
It's a technology already used at utilities companies to understand for instance if a household has electric or gas hobs.