  This paper introduces Waste Factor (W), also denoted as Waste Figure (WF) in
dB, a promising new metric for quantifying energy efficiency in a wide range of
circuits and systems applications, including data centers and RANs. Also, the
networks used to connect data centers and AI computing engines with users for
ML applications must become more power efficient. This paper illustrates the
limitations of existing energy efficiency metrics that inadequately capture the
intricate energy dynamics of RAN components. We delineate the methodology for
applying W across various network configurations, including MISO, SIMO, and
MIMO systems, and demonstrate the effectiveness of W in identifying energy
optimization opportunities. Our findings reveal that W not only offers nuanced
insights into the energy performance of RANs but also facilitates informed
decision-making for network design and operational efficiency. Furthermore, we
show how W can be integrated with other KPIs to guide the development of
optimal strategies for enhancing network energy efficiency under different
operational conditions. Additionally, we present simulation results for a
distributed multi-user MIMO system at 3.5, 17, and 28 GHz, demonstrating
overall network power efficiency on a per square kilometer basis, and show how
overall W decreases with an increasing number of base stations and increasing
carrier frequency. This paper shows that adopting W as a figure of merit can
significantly contribute to the sustainability and energy optimization of
next-generation wireless communication networks, paving the way for greener and
more sustainable, energy-efficient 5G and 6G technologies.
