Bitcoin mining overall cannot be made more efficient in terms of real cost. Given that all costs resolve to energy, this could be restated as, Bitcoin cannot be made more energy efficient. Paradoxically, no matter what technology improvement is introduced, the cost of transaction confirmation remains the sum of the reward for confirmation.

This apparent contradiction arises from the fact that reward ultimately determines cost. An increase in hash rate for the same cost results in a difficulty increase to maintain the block period, increasing cost accordingly. Bitcoin mining must always consume in cost the amount of its current reward.