I finally put the effort in to do a test. It helped that I already had a pre-built titanium boiler / large turbine setup in Creative.
Running 128 charcoal through the boiler consumed 29,600 L of water. The large turbine returned 26,900 L of water. So, only 2,500 L of water destroyed during startup, far less than the 17,000 L I estimated, or the amounts I thought were being consumed each cycle in actual usage.
A single-block distillery produces 6 L/sec distilled water at a cost of 32 EU/L. A 128v distillery produces 12L/sec for 64 EU/L. 5,000 L water destroyed per cycle by 2 boilers = 160k EU to replace at 32V, or 320k EU at 128v.
The distillation tower produces 625 L/sec of distilled water at a cost of 3.8 EU/L at 128v. It’s 100x as fast as the LV block, which is understandable given that the material cost is around 30x as much and uses more valuable materials, and 8.3x as energy efficient.
Interestingly enough, the distillation tower recipe destroys water, since it’s 576 L water in and 520 distilled water out, and the single-block recipe is 5L for 5L. I don’t really care, since it’s the destruction of water inside the distilled water loop that concerns me, not the original source water.
I don’t think I’ll put in the investment. 320k EU/cycle is about a 1.5% loss, and doesn’t warrant the cost and effort of a distillation tower.