copy&paste from another reactor thread that I replied to:
The main recipe is deuterium + tritium cells which produces 1 helium plasma cell. The process takes 128 ticks and the cell can be turned into 8192k EU in a plasma generator, so this gives you 64000 EU/t. (requires 31.25 plasma generators)
However the fusion process requires 4096 EU/t to keep the reactor heated up, so you effectively get 59904 EU/t.
Let's look at the fuel production:
You will need 1 tritium and 1 deuterium every 128 ticks = 6.4 seconds. 1 tritium needs 4 deuterium in a centrifuge and 1 deuterium needs 4 hydrogen cells in a centrifuge. Each process takes 150 seconds so you'll need a lot of centrifuges to keep up with the reactor!
How many?
144 !!
24 centrifuges for deuterium to tritium (150 seconds / 24 = 6.25 seconds) for which you'll need 24*4=96 centrifuges turning hydrogen into deuterium.
another 24 centrifuges turning hydrogen into deuterium for the reactor itself
so:
120 centrifuges for hydrogen to deuterium and
24 centrifuges for deuterium to tritium
Now we also need to create all that hydrogen.
To make it short: you need 30 electrolyzers for that. (5*4 hydrogen / 6.4 seconds ~ 30*4 hydrogen /38 seconds)
so assuming you are not using overclocked machines:
144 centrifuges * 5 EU/t + 30 electrolyzers * 120 EU/t =4320 EU/t for fuel production.
This results in a total EU gain of 55584 EU/t. (a little bit more than that, because we have a very small fuel overproduction)
Regarding overclockers:
Each overclocker cuts the processing time in half and doubles the energy required per process.* (so the EU/t goes up by a factor of 4)
Personally I'm using 3 overclockers in each of the centrifuges, which cuts down the required number of centrifuges to 18, which is quite reasonable for the server to handle. (Overclocking the electrolyzers would obviously be a bad idea.)
The total power consumption of the centrifuges goes up by a factor of 8 so my fuel production needs 5*144*8 EU/t + 120*30 Eu/t = 9360 EU/t so about double of the design with 144 centrifuges.
Thus my total energy gain with this system is about 50000 EU/t.
TLDR: use 30 electrolyzers without OCs and 18 centrifuges with 3 OCs each (will require HV so you will need to use some transformer upgrades)