Watt is the electrical unit for the rate at which energy is generated or consumed. If a lightbulb has 100-watts, it uses 100 watts of electricity for every second it’s on. A kilowatt equals to 1,000 watts, and a kilowatt hour is how much energy was used to generate 1 kilowatt of power in 1 hour.
A common misconception is that the brightness intensity is based on watts. Brightness is measured in a different unit called lumens, so don’t hesitate to get some efficient low-wattage bulbs.
The word watt comes from the 19th century scientist James Watt, known best for contributing to the invention of the steam engine. He also created the unit known as horsepower, which refers to the power of the steam engine. This concept came from his calculations that one mill horse was able to move 33,000 pounds in one foot per minute (foot-pounds). Today, we now use horsepower to measure the strength of locomotives, automobile engines, vacuums, and other machinery.
What does this have to do with watts? Well, mechanical power is energy that results from moving machines. In the same sense, electrical power results from moving electrons, which is also mechanical energy. And while mechanical power—measured in horsepower—is easy enough to recreate with a mill horse and some weight, electricity is a little trickier to measure with a mill horse. (??) Also, 1 horsepower equals 746 watt. The watt is the logical unit of measurement to use for electricity, however, and it’s what we continue to use today.