In Cuba, the electrical system used is the U.S., ie flat blade 110V 60Hz, that's the one in all the houses. This creates a problem because Cuba due to the economic embargo is forced to import electrical equipment from other markets, especially in Europe. Since the European system is 220V 50Hz round shank, in Cuba it has become imperative to also have this voltage in all hotel facilities and in many houses.
As a result of this, in all the hotel facilities and the vast majority of private accommodations, the guest can have 100V outlets and 220V interchangeably. No need to bring adapters, much less voltage transformers, to use your electrical devices during your stay in Cuba. In the unlikely event that a guest brings a device with a very specific electrical outlet, the hosts of private accommodation will deal to solve the problem in a way you can use your equipment normally.