2000L of Hydrogen can be produced by electrolyzing 3000L of Water at 30 EU/t (LV) taking 100s (2000 ticks). This consumes 60,000 EU per 2,000L so 30 EU/L.
4L of Deuterium can be produced by centrifuging 16L of Hydrogen at 20 EU/t (LV) taking 0.8s (16 ticks). This consumes 320 EU per 4L so 80 EU/L + 30 EU/L (Hydrogen) = 110 EU/L.
4L of Tritium can be produced by centrifuging 16L of Deuterium at 80 EU/t (MV) taking 0.8s (16 ticks). This consumes 1280 EU per 4L so 320 EU/L + 110 EU/L (Deuterium) = 430 EU/L.
125L of Helium Plasma can be produced by fusing 125L of Tritium and 125L of Deuterium at 4096 EU/t (IV) taking 0.8s (16 ticks). This consumes 65536 EU per 125L so 524.288 EU/L + 430 EU/L (Tritium) + 110 EU/L (Deuterium) = 1,064.288 EU/L.
However, in order to start the reaction the reactor first consumes 40,000,000 EU.
1,000L of Helium Plasma is worth 4,096,000 EU when consumed by Plasma Generator. This means it has an energy value of 4,096 EU/L, which is about 3.85x more energy than its consumption.
The problem is of course the kickstart 40 mil EU. The net gain can be calculated as (4096 / 1064.288)x - 40000000 where x is the amount of Helium Plasma to produce per 1 cycle. So the net gain can only be positive when the batch size is more than:
(4096 / 1064.288)x - 40000000 > 0
(4096 / 1064.288)x > 40000000
x > (1064.288 / 4096) * 40000000
= 10393437.5
... whopping 10,393,437.5 L (10393.4375 buckets) of both Deuterium and Tritium. But don't forget that "low tier" Plasma Generators have poor efficiency. The mark I generator outputting EV can only do it with 50%, doubling the size of the smallest possible batch.
So no, never try to do it with a batch size something like 600 buckets. It is far more than you think.
With no overclocking (preferred!), it takes 2000 ticks to produce 2000L of Hydrogen. This means its production rate is 1 L/t.
For Deuterium and Tritium it takes 16 ticks to produce 4L by consuming 16L of Hydrogen. So the production rate is 0.25 L/t and the consumption rate is 1 L/t.
Overclocking is not recommended for fuel production because it never comes without penalty. It makes no sense to waste EU to generate EU.
For Helium Plasma it takes 16 ticks to produce 125L by consuming 125L of Deuterium and Tritium. So the production rate is 7.8125 L/t and the consumption rate is also 7.8125 L/t.
But at the same time Deuterium is also used for producing Tritium. Its overall consumption rate is therefore 7.8125 + x L/t where x is the number of MV centrifuges for Tritium production.
If you need to run the reactor nonstop, things go real crazy...
To keep up with the fuel consumption 7.8125 L/t, you need to produce Tritium with at least 31.25 MV centrifuges. Processing Array comes in handy here. You only need two processing arrays with 16 MV centrifuges, each running on EV. This incurs no overclocking penalty.
Assuming you have 32 MV centrifuges for Tritium production, the consumption rate of Deuterium is 7.8125 + 32 = 39.8125 L/t. This means you need at least 159.25 LV centrifuges. Since a single Processing Array can only run at most 16 machines, this means you need 10 processing arrays running on HV.
Assuming you have 160 LV centrifuges for Deuterium production, the consumption rate of Hydrogen is 160 L/t. This means you need at least 160 LV centrifuges, again 10 processing arrays running on HV.
10 processing arrays (HV) for Hydrogen, 10 (HV) for Deuterium, 2 (EV) for Tritium. 1 IV for Helium Plasma.
20 HV = 5 EV, 5 + 2 EV = 7 EV < 2 IV, 2 + 1 IV = 3 IV. Yes, you need 3 amperes of IV (or 1 ampere of LuV) to run the entire system nonstop.
Fusion Control Computer Mark I cannot do any overclocking. Mark II does 2x overclocking if the kickstart energy is less than 160,000,000 EU. Mark III does 4x overclocking if the kickstart energy is less than 160,000,000 EU, and does 2x overclocking if the kickstart energy is less than 320,000,000 EU. This incurs no penalty. It simply doubles (or quadruples) the energy consumption rate and halves (or quarters) the processing time.
However, even with no overclocking it requires 22 processing arrays to run nonstop. By overclocking it with Mark II you need 44 processing arrays. For Mark III you need 88. This is hardly practical.