One of the key challenges in G.fast is to minimize the power consumption at distribution points. G.fast standards define Discontinuous Operation modes that provide avenues for power reduction by allowing intermittent transmission of users along time slots. In this paper, we formulate a power efficiency problem as a user-slot assignment problem, where we schedule users to time slots during discontinuous operation such that the total power consumption is minimized. Since the general user-slot assignment is NP hard, we propose a weighted $A^{*}$ algorithm based solution that achieves reasonable performance with limited computational resources. Further, the proposed user-slot assignment is also G.fast standards compliant and therefore can be implemented in practice. We also explore different precoding as well as user grouping strategies that can be employed while performing user-slot allocation. Finally, the main insight of this work is that on using our user-slot assignment algorithm and by only precoding during the normal operations, we achieve energy efficiency levels comparable to those achieved when precoding is applied during the discontinuous operations without the suggested user-slot allocation.