How many watts could a windmill generate?

Hypothetically, if i were to hook up an old timey flour windmill to a generator, how much power could i produce with its rotation?

Depending on one’s use case, one can also use a windmill, of any age, to directly generate hot water. Mostly useful if the end use for those watts is hot water. This is more efficient than wind to energy to hot water.

Edit to add: To get ahead of the obvious, but stupid question.

No, likely not hot enough to make steam to spin a different windmill/turbine to make electricity.