Effects be on the car if it is not driven for over a year?

Hello,

It will depend on several different variables. Like the weather (geographic location) if it will be parked indoor or outdoor etc.

If is it parked in a clean garage and stays mostly clean/covered, you might not have too much to worry about. You will need a new battery first of all. Also, might need some fuel additive to rejuvenate the fuel.

If it is outside in the elements, then it is possible that the impact would be much more severe. Besides needing a battery, it is likely you will have to do a thorough cleaning under the hood. Clean out the throttle body and any other components that might have dirt. The fuel could be in worse shape. You might have to drain the fuel and use fuel additive and fresh fuel. It is also possible to have dry rotted hoses. You might also have some leaks that will need to be addressed.

Will likely need a tune up and cleaning of components.

https://www.2carpros.com/articles/how-to-tune-up-a-car-engine

So really it will all depend on the weather as well as the vehicle overall condition.

Hope this helps.

Please let me know of any questions.
Thank you.