The unit of power in the SI system is what?

The unit of power in the International System of Units (SI) is the watt. Power is defined as the rate at which work is done or the rate at which energy is transferred or converted. One watt is equivalent to one joule per second, indicating that if one joule of energy is used in one second, a power of one watt is being exerted.

In the context of other units listed, a joule measures energy, a newton measures force, and a pascal measures pressure. While they all belong to the system of measurements that describe different physical quantities, power specifically describes the rate of energy transfer, for which the watt is the appropriate unit.