[atq2119]

If I remember my long ago physics classes correctly, irreversible computation inherently costs energy: you can't get its energy "consumption" down to zero because of entropy, no matter how efficient the technology. Our computer architectures are far from reversible in a physical sense. If they were, you could run programs in reverse. That said, the minimum amount of energy required is an absolutely tiny rounding error compared to the waste heat of today's technology.