IEEE 802.11ac WLANs propose the use of 80 and 160MHz bandwidths. Over such bandwidths the large frequency variability of the channel motivates the dynamic allocation of resources per OFDM subcarrier. In this work we focus on power adaptation (power loading). Besides physical layer performance analysis, we account for protocol overhead and for practical implementation issues in WLANs. In particular, we consider the exploitation of coherence time in 80MHz TGac indoor channels trading-off algorithm accuracy for channel estimation overhead. We further study the trade-off between algorithm performance and computational complexity to conclude that optimal solutions do not necessarily perform better than sub-optimal low-complex ones. We show that pure power loading provides only a modest performance gain compared to static schemes and propose power loading combined with the deactivation of highly attenuated subcarriers as a candidate approach for improving WLAN.