Depending on the context I would say:
De hora a hora y media.
Entre hora y hora y media.
When you have one as the minimum of your time range and no more than two as the maximum, you can omit that in Spanish.
De hora a hora y media.
De una hora a dos horas y media.
But, on the other hand, when you have a different minimum, you can omit the time "unit":
De tres a tres horas y media.
De diez a veinte años.
