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| Symbol | Definition |
|---|---|
| ≡ | exactly equal |
| ≈ | approximately equal to |
| = | equal to |
| digits | indicates that digits repeat infinitely (e.g. 8.294 369 corresponds to 8.294 369 369 369 369 …) |
The kilowatt (kW) is equal to one thousand (103) watts. This unit is typically used to express the output power of engines and the power of electric motors, tools, machines, and heaters. It is also a common unit used to express the electromagnetic power output of broadcast radio and television transmitters.
The petawatt (PW) is equal to one quadrillion (1015) watts and can be produced by the current generation of lasers for time-scales on the order of picoseconds (10−12 s). One such laser is the Lawrence Livermore's Nova laser, which achieved a power output of 1.25 PW (1.25×1015 W) by a process called chirped pulse amplification. The duration of the pulse was roughly 0.5 ps (5×10−13 s), giving a total energy of 600 J.