This is always used as an argument against going electric, but it's flawed for a few reasons.

1st, that 94% doesn't hold everywhere. I live in NZ. We're at about 80% renewable for grid energy.

2nd, the type of people who can afford, and choose to go electric for environmental reasons, are the same people who are likely to be installing solar panels and other renewables at the property.

3rd, even you have pointed out that your 94% figure is well out of date... because most governments (Except a few derps) are trying to increase the percentage of renewable energy in their grids. I'm not sure where you are, but assuming you're in the US, it's actually 78% now, and 60% for the UK

4th, the cars themselves generate power through solar, and regenerative breaking. No, it's probably not enough to keep you running without plugging in to the grid, but it is a further reduction.

There are environmental issues related to electric cars, but they're in the manufacturing. Not in the reliance on grid energy. Assuming that the car survives it's full lifecycle, even only relying on grid power with their current percentages of renewables, the overall impact is STILL a net reduction in emissions.

There are plenty non-environmental reasons for going electric too

TL;DR: Ye, nah, the grid energy argument doesn't hold water. Love it or hate it, electric cars are the future.