Once we get the ridership numbers up we can easily make up for the electricity efficiency.
My understanding is the electricity efficiency is really just a nice bonus (or perhaps justification) for making improvements that would also increase ridership.
I'm only loosely aware of the Electric Fleet, but my understanding is they add capacity that was desperately needed.
Get the rider numbers up and extend the lines. Thats the only thing we need right now.
The above if done across the whole metro should get 30% mode share across the merto which would be world class. It would also cost about $200 per month per adult - which is a lot cheaper than a car - but still massively more than any city spends on transit.
Most if not all electric trains powered by overhead wires have regenerative braking that feeds back to the grid as standard, and Caltrain's new Stadler units definitely do. Nobody paid extra for regenerative braking, it's just the default way to do things on electric trains, to the point that it'd be weird not to have it. Even diesel-electrics often have a kind of regenerative braking, but they don't have anywhere to store the recovered energy so they just convert it to heat via huge resistors.
However, since this has been normal in Europe and Asia for decades, I doubt the additional expense is significant.