I have 4 fans in the same room If I install the necessary piece in each fan, can I then use 1 remote for all or do I need all 4 remotes?

You can, but what often happens, even with just 2 is, 1 May receive the signal, other won't, then they are out of sync(Pressing the light button may turn 1 on, and turn the other off).
Then you have to try to get transmitter to be received by 1 to get back in sync. With 4 this will be tougher.
Try it, If you have a good strong signal, you may not have a problem.
Good Luck

I recommend against using remotes, especially for multiple fans. Just use wall controls.

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