I   Quick reference

SI Units

The watt. This SI unit is named after James Watt. As for
all SI units whose names are derived from the proper name
of a person, the first letter of its symbol is uppercase (W). But
when an SI unit is spelled out, it should always be written in
lowercase (watt), with the exception of the “degree Celsius.”

from wikipedia

SI stands for Système Internationale. SI units are the ones that all engineers
should use, to avoid losing spacecraft.

SI units
energy onejoule 1 J
power one watt 1 W
force one newton 1 N
length one metre 1 m
time one second 1 s
temperature one kelvin 1 K
prefix kilo mega giga tera peta exa
symbol k M G T P E
factor 103 106 109 1012 1015 1018
prefix centi milli micro nano pico femto
symbol c m μ n p f
factor 10-2 10-3 10-6 10-9 10-12 10-15

My preferred units for energy, power, and transport efficiencies

My preferred units, expressed in SI  
energy one kilowatt-hour 1 kWh 3 600 000 J
power one kilowatt-hour per day 1 kWh/d (1000/24) W    40 W
force one kilowatt-hour per 100 km 1 kWh/100 km 36 N
time one hour 1 h 3600 s
  one day 1 d 24 × 3600 s    105 s
  one year 1 y 365.25 × 24 × 3600 s    π × 107 s
force per mass kilowatt-hour per ton-kilometre 1 kWh/t-km 3.6 m/s2 (  0.37 g)
Table 1.1. SI units and prefixes