Do electric cars really help the environment and how?

 They are certainly much better for the environment than internal combustion engine (ICE) cars, both due to dramatically-reduced local emissions, and due to much higher efficiency, which when combined with either a low-enough grid carbon intensity, or your own clean (e.g. rooftop PV) power, makes for greatly reduce emissions from transport. Another advantage is that the grid intensity can improve over time and thus the vehicle emissions fall after purchase, unlike an ICE vehicle. Other answers go into much more detail about what grid intensity produces a better overall result, so I won’t repeat that here.

Of course electric cars are nothing like as good for the environment as walking or cycling or using the bus, tram or train. EVs do not solve any of the problems of congestion, road danger, urban sprawl, noise (well a bit, but surprisingly little - it’s nearly all tyre/wind noise), resource use and inefficient use of space.

So, yes stop selling fossil cars pretty-much immediately and sell electric ones instead, but don’t promote private car use over the other transport solutions, at least not in urban areas, because it is a problem much more than it is a solution in that environment. If this seems like a very strange thing to say, then I suggest you visit a city with good cycling and public transport infrastructure and experience what it’s like when the place is not dominated by cars. It’s a revelation. In the meantime try some of Clarence Eckerson Jr’s Streetfilms to get some idea of what a place can be like when cycling is prioritised:

Electric cars are zero emission so their operation generates no pollution, but that’s only true if you only examine it from tailpipe emissions and not the whole story when you consider the entire product cycle, not from cradle to grave, but from cradle to cradle including manufacture and recycling.

It takes an enormous amount of energy to manufacture batteries and there is no current infrastructure to recycle spent (EV) batteries. Of course the power source to charge an EV is also an important consideration, plus the extensive use of lightweight materials - aluminium is more energy-intensive to produce and recycle than steel, and plastics are virtually not recycled but burnt as fuel since virgin plastic is cheaper than recycled plastic.

The optimal solution to any problem is often multifaceted rather than sole source, and problems themselves are often difficult to identify, or often ignored because they don’t contribute to profits. Then there are often conflicts with government mandates and corporate capabilities to consider.

If you don’t know how to make internal combustion engines or how to optimize them, then you’re likely to gravitate toward sticking some batteries and electric motors in a chassis and call it a car; the simplicity of it (taken within context) has even attracted companies such as Dyson and others into the game - would you buy a car made by a vacuum cleaner maker? and are they motivated by opportunity and profit rather than the environment?