The unit of measure of power used in the SI system is:

The unit of measure of power in the SI (International System of Units) is indeed expressed in watts, where one watt is equivalent to one joule per second. When discussing larger quantities of power, kilowatts, which are 1,000 watts, are commonly used. This is particularly true in contexts such as electrical power generation or consumption.

Power quantifies the rate at which energy is transferred or converted, making kilowatts a practical measure for evaluating energy efficiency and capacity. For example, electrical devices and engines are often rated in kilowatts, reflecting their performance and energy consumption.

In contrast, newtons are the unit of force, joules represent energy or work done, and work, although related to power, is fundamentally a measure of energy transfer and is not a unit of power itself. This differentiates why kilowatts is the most appropriate answer in the context of power measurement within the SI system.