Lightweight hash functions have become important building blocks for security in embedded and IoT systems. A plethora of algorithms have been proposed and standardized, providing developers with a wide range of performance trade-off options. This paper presents a comparative analysis of 22 software-based lightweight hash functions, including submissions from the NIST lightweight cryptography standardization process, ISO, and the SHA-3 competition. We use a novel benchmark methodology that combines an AVR ATXMega128 microcontroller with the ChipWhisperer power analysis toolset. We evaluate and compare the various hash functions along several dimensions, including execution speed, memory footprint, and energy consumption. Using the composite \({{\,\mathrm{E\text {-}RANK}\,}}\) metric, we provide insight into the various trade-offs and overall efficiency each hash function offers to system developers.