You will find many guides on the net about how to make alot energy credits. So people suggest to play certain STFs and sell the equipment... other suggest to take part in the race.
Everything right.. everything works.
However... in my eyes this takes too much time.
I tell you how to earn a few million ec in just one hour.
1. You need to be a Vice Admiral (I actually dont know if it works that good for lower ranks.... but i assume that its still ok for them)
2. Set the game difficulty to ELITE (this makes the game of course harder... but has the very positive effect that you get better loot)
3. Now play to the Eta Eridiani sector block and enter the Ker'rat warzone
This is were the money making starts.
Task is to destroy as many cubes, spheres, probes and most important the repair hulks as possible. If your DPS is high enough you can even attack the Tactical cube... if not just ignore them.
Practically everything in that system drops loot.
Best is if you play with others and scan the 8 encryption nodes... once done practically everything turns hostile and you can start shooting.
Almost everything in this system drops loot... good loot (up to very rare mk xii items).
Collect everything, disband the junk and once the inventory is full (that does not take long) leave the system, fly to K-7 or call the Azura and put these items on the exchange.
Now enter Ker'rat again and start your 2nd round.
Thats... you get dunno... maybe 4-5mio ec per hour.