SHA- 256, but is millions (maybe billions) of times more energy efficient than a general-purpose CPU evaluating SHA-256. The relevant specs for Bitcoin mining hardware are wattage and giga-hashes (or tera- hashes) per second, which can be converted into raw energy required per hash. Search online and find the most energy efficient mining hardware you can (e.g., least joules per hash). I found the Antminer S19 Pro, which operates at 29.5 J/TH. Find the cheapest real-world electricity rates you can, anywhere in the world. Use these to estimate the monetary cost of computing 240, 250, . . . , 2120 SHA-256 hashes.