We can currently support a sizable number of PHEVs with our current infrastructure. Since cars are by far the largest consumers of petroleum fuel the effect would be sizable. The key is to add incentives to purchasing them over traditional engined cars.
Until batteries undergo a complete revolution in capacity electric cars will only be a novelty for city drivers. I can just imagine the line of a couple hundred cars at a turnpike rest stop waiting a couple hours to recharge their car. You mention "average range", and my average commute is 32 miles, but my "desired range" is at least a thousand miles if not more, which is possible with a few short 10 minute fill-ups. A car without such a range would not be something I'd ever consider buying as a primary car.
I see two paths forward for emission-less cars, developing batteries with larger capacities/building more nukes and also more efficient extraction of hydrogen and developing sturdier fuel cells. Some of the gen 4 nuclear reactors are designed to purely pump out waste heat which can be used to produce hydrogen (using petrochemicals unfortunately, but far more efficient than electrolysis).
While you mention Solar the problem of course is off-peak consumption coincides with off-peak electrical production for Solar. I see Solar / Wind as always being a novelty as well until we find better storage devices. I believe Canada uses gravity pumps to store off-peak power, but this isn't terribly efficient.