I'm planning to drive my UK-registered electric vehicle in the Netherlands and Germany. I may (by design or accident!) drive in a low emissions zone in either country. Do I need to have a sticker on the car, or do these only apply to petrol/diesel cars?
In Germany, the answer is yes: If an area is restricted you need a sticker (“Umweltplakette”) even if your vehicle is electric and obviously qualifies. Comments mentioned the fact that you can order it online and some exceptions for cars with another national sticker or special number plates but you definitely need a marker of some sort. Otherwise, you will have to locate some certification bureau that can issue the sticker. It's been a long time since I did it but as far as I know you get a sticker on the spot for a small fee, based on the car's registration papers. You do have to plan for 15 minutes and check their opening hours (the most annoying thing if you travel on a week-end).
In the Netherlands, there is no sticker and you do not have to do anything in advance. Enforcement is fully automated for Dutch number plates and you can check online if your car qualifies. For foreign number plates, it's up to you to check the rules and enforcement is obviously more difficult but if your car does qualify, you can simply drive in the restricted area without any formalities. Exact restrictions vary depending on the city but for cars, they only impact diesel engines and an electric vehicle obviously qualifies.