Which cars come first and when depends on CO2 emissions requirements, Blume said.

It won't surprise you to hear why they're sharing resources: money. Blume said it would cost about 30 percent more for each brand to develop their own EV platforms. It won't be a trivial expense even then. Stadler estimated that it would require a "low single-digit billion euro sum" to develop the platform by 2025.

This is separate from the Mission E, which remains Porsche's current focus. And this doesn't preclude either company from building custom platforms when their goals demand something specific -- we'd expect Porsche to go that route for sports cars. However, it does give you a good idea of what to expect when EVs hit the market in earnest. As with some conventional cars, the biggest differences between EVs may revolve around power plant choices and styling rather than their underlying designs.