The one thing I always wonder about these schemes, is reimbursing the battery owner for the wear and effective use of charge cycles. Batteries are (very expensive) consumables, so pulling power from idle batteries comes with a background cost to the owner.
Green Energy
Everything about energy production and storage.
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What is the use case for an EV to provide power to the grid?
Peak times vs. off peak.
This makes sense to me.
Charge car overnight offpeak costs, power house during peak hours
Here’s one scenario: Go to work with a partial charge, charge during the day using excess solar production when electricity is super cheap, drive home fully charged, sell some power to the grid during peak domestic use hours, keep enough to safely get back to work, repeat.
The highest few hours of peak demand each year. It can make sense to use relatively expensive storage for that because you're using it infrequently.
The use case (as opposed to public transit and stationary grid batteries) is that rich people get to feel good about themselves while still being subsidized by and separated from the working class.
If utilities have to pay car owners an realistic amount for prematurely degrading their batteries this would be uneconomical. Thus this is either hoping for car-owners being ignorant and only realizing it a few years later or it will never take off.
Usually it is no problem for utilities to get a loan for installing grid tied batteries, as it is nearly an guaranteed payback and they can either buy better suited battery technology or recycled car batteries in bulk for it.
Maybe if the technology allows running them completely separate from the grid for personal battery backup and utilities finally pass through off-peak electricity prices to customers so that it makes sense for home owners to use their batteries during peak hours...
I don't think it'll be economical for a daily cycle, but there's a good chance this comes out as a reasonable choice for the 10-15 highest-peak-demand hours per year.