Concept 
SI unit 









There are SI units for many any and all useful physical quantities,
of which just a few are given in the table below. Importantly, the SI system
is a system. If you put SI values into a formula for all quantities, the
answer always comes out in SI units.
On the Internet, it is not easy to express superscripts without using pictures that take too much time to load. Therefore, we use a caret to express the exponent. For example, we use m^2 to represent square meters. 



























It is important to remember that energy is measured in joules, and
power is measured in watts. One joule = 1 watt ´
1 second. People usually associate the watt with electricity, but that
is because the SI system has traditionally been used only for electricity
in the US. The watt is a general unit for power  energy divided by time
 regardless of whether electricity is involved.
The socalled power company sends you a bill for energy (not power), but it uses a nonSI unit for time. To get the energy, they multiply kilowatts by hours to get kWh. 
For more information,
see National Institute for Standards & Technology (NIST)