Depends on your goals.
If you would like to plunk out a few melodies, with minimal left-hand accompaniment, it is not too difficult. I would say a few months to a year you will be on your way. Factors that are important to consider though.
If you would like to play Classical piano at say grade 8, or early advanced level. Give it a decade from a standing start. In addition to the points above I would add the following: learn to love every aspect of the game. Do not skip a step: technique, repertoire, ear training, theory, history, etudes, etc. There are no hacks or shortcuts.
If you would like to play Jazz piano in a band, assuming you have already reached level 8 in abilities, give it a couple of years. All the points above are valid with the addition of a few other steps.
If I can help, please call.
You've got to learn your instrument. Then, you practice, practice, practice. And then, when you finally get up there on the bandstand, forget all that and just wail.
I'm a professional pianist and music educator in West Toronto Ontario. I'm also a devoted student and teacher of the drums.