The correct way to say something is hired on an hourly basis [closed]

Which of the following is correct?

We hire our bicycle...

  1. by the hour.
  2. by hours.
  3. by an hour.
  4. for hours.

Regardless of whether OP is hiring ("renting" in the US, apparently) bicycles as a supplier or as a customer, if the standard charging unit is an hour, said bicycles are hired/rented by the hour.