We think the Swedish bike rack and carrier company Thule offer superb options for e-bikers. None of us are going to want to put an electric bike on the roof, and unless you have a neat folding Gocycle to put in the boot, then you're looking at a towbar bike rack. Electric bikes tend to be heavy, so this is the only option really.
Thule offer excellent options like the EasyFold, the EuroClassic G6, or the VeloSpace. All are suitable for e-bikes, and have simple, effective locking mechanisms.
Check them out here, and visit the Thule site.