Estimates place Bitcoin’s current energy consumption at 141.83 terawatt-hours/year, an amount comparable to Ukraine. While Bitcoin’s energy problem has become increasingly visible in both academic and popular discourse (see Lally et al. 2019), the computational mechanisms through which the Bitcoin network generates coins, proof-of-work, has gone under-examined. This paper interrogates the “work” in proof-of-work systems. What is this work? How can we access its material history? I trace this history through a media archaeology of computational heat, in an attempt to better situate the intimate relationship between information and energy in proof-of-work systems. I argue the “work” in these systems is principally heat-work, and trace its ideological constructions back to nineteenth-century thermodynamic science, and the reframing of doing work as something exhaustible, directional, and irreversible (Prigogine & Stengers 2017; Daggett 2019). I then follow thermodynamic discourse through Cybernetics debates in the 1940s, illustrating how, early in the formation of Information Theory, the heat-work undergirding the functioning of a “bit” was obscured and compartmentalized, allowing information to be productively abstracted apart from its energetic infrastructures (Hayles 1999; Kline 2015). I conclude with a discussion of the heat-work within the Application Specific Integrated Circuit (ASIC), Bitcoin’s principal mining tool, arguing that proof-of-work mining is not a radical exception to the computing status quo, but rather a lens through which to think more broadly about computing’s complex relationship to energy, and ultimately, how this relationship can be different.