The electricity will be reduced by the fact that Round 1 is not computing-intensive and most of the miners won't be "allowed" by the rules (if followed) to advance to the second round. The second round will be only among the first N2. This will reduce the electricity greatly.

In the traditional PoW, all miners are hashing for big complexities most of the time. While TRPow round 1 complexity is not electricity intensive. The complexity of Round 1 will be set to be small. So Round 1 is pure Luck and Round 2 is where the calculation power is needed.