Joule
A joule (symbol J) was a unit of energy. Comparable units included electronvolt and calorie.

Comparative list of energies 
Microjoule = 0.000,001 joules
microjoules: In 2368, William T. Riker told Soren to rechannel every single microjoule to the transporter systems on the Magellan to escape disaster. ()

Millijoule = 0.001 joules
5 millijoules: Tom Paris used a cardio-stimulator to cajole the heart of 's son to life. Although the initial charge of 3 millijoules was unsuccessful, the second charge set at 5 millijoules was successful. ()
20 millijoules: The starting dose of energy with a cortical stimulator was 20 millijoules. ()
30 millijoules: A simulation of potential surgery for Seven of Nine was ended by The Doctor when he was forced to raise a neurostatic pulse from 20 millijoules to 30 millijoules. () 
50-70 millijoules: In 2376, a cortical simulator using an energy pulse at 50 and 70 millijoules was used successfully to save B'Elanna Torres after she suffered complications from oxygen deprivation. ()
75-90 millijoules: In 2375, a cortical stimulator using an energy output of 75 and 90 millijoules was unable to save the Silver Blood duplicate of B'Elanna Torres. ()
 300-350 millijoules: Despite using 300 and 350 millijoules on Hoshi Sato, Phlox was unable to resuscitate her following infection from a silicon-based virus. ()

Joule
0.2 joules (= 200 millijoules): Phlox increased a cardio-stimulator's output by 0.2 joules in order to help save Major Hayes' life. ()
25 joules: Using an equal energy output of 25 joules, Jadzia Dax and Worf were able to link their tricorders on a mission during the Dominion War. ()

Kilojoule = 1 thousand joules 
4.3 kilojoules: The weak and primitive deflector shield protecting the Lysian Central Command had an output of only 4.3 kilojoules and could have easily been taken out with a single photon torpedo. ()

Megajoule = 1 million joules
1.05 megajoules: a standard Federation phaser rifle could output 1.05 megajoules per second with a beam. ()
2.1 megajoules: The ship-mounted disruptor weapon capacity of a 24th century Lysian destroyer was rated at 2.1 megajoules. ()
4.7 megajoules: A hand-held Cardassian phase-disruptor rifle had a 4.7 megajoule power capacity, three-millisecond recharge, and two beam settings. ()
5 megajoules: Starfleet phase-pistols of the 22nd century were generally kept under 5 megajoules of power output. ()
10 megajoules: Malcolm Reed discovered that increasing the output of phase-pistols to 10 megajoules added enough energy to destroy Borg shielding. ()
10 megajoules: Using an annular confinement beam during investigation of null space, the Magellan used up 10 megajoules, taking their energy reserves from 34% to 9%. ()

20 megajoules: In an attempt to activate a scanner discovered in the Gamma Quadrant, Data suggested transferring 20 megajoules of energy from the dilithium chamber into the plasma inputs of the device. ()
37 megajoules: When transporting a test cylinder to a Romulan science vessel through a micro-wormhole, B'Elanna Torres ordered for power to the phase transition coils to be increased to 37 megajoules. ()
40-50 megajoules: When converting energy to power a derelict Xindi-Insectoid assault shuttle, Charles Tucker III originally used 40 megajoules of power from , before raising it to 50 megajoules. Due to problems with the matrix converter, they were unable to continue powering the shuttle directly. ()
600 megajoules: The unidentified aliens placed a device on board Enterprise which ran with a tremendous amount of energy, over 600 megajoules. ()
800 megajoules: The Nechisti shrine had 800 megajoules of biogenic energy running through it. ()

Gigajoule = 1 billion joules
4.6 gigajoules: The Breen CRM 114 was capable of cutting through shields with an output of up to 4.6 gigajoules. ()
80 gigajoules: 22nd century Starfleet phase cannons had multiphasic emitters and a maximum yield of 80 gigajoules. ()
500 gigajoules: These phase cannons were rated for a maximum power output of 500 gigajoules. ()

Terajoule = 1 trillion joules
30 million terajoules (=30 exajoules): The graviton ellipse contained 30 million terajoules of subspace energy. ()
30 million-90 million terajoules (=30-90 exajoules): A neutronic gradient encounter by the  rose from 30 million to 90 million terajoules of energy before hitting the vessel and causing widespread system failures. ()

Exajoule = 1 quintillion joules
100 exajoules: The 's attack on Harlak generated a power surge in the 100 exajoule range that was detected by the  in the planet's orbit. ()

External links

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Measurements
Energy