# 5.3 Energy Consumption & Ecology ###### tags: `Blockchain` The following notes are taken from [Coursera](https://www.coursera.org/learn/cryptocurrency/home/week/2) --- ### Thermodynamic Limits :::success - **Landauer's Principle:** Any non-reversible computation must consume a min amount of energy - Specificaly, each bit changed requires (kT in 2) joules ::: - **SHA-256 is not reversible** :::danger Energy consumption is inevitable ::: ### Energy Aspects of Bitcoin Mining - **Embodied energy:** used to manufacture mining chips & other equipment - should decrease over time - returns to scale - **Electricity:** used to perform computation - should increase over time - returns to scale - **Cooling:** required to protect equipment - costs more with increased scale ### Estimating Energy Usage: Top-down - Each block worth approximately $15, 000 - Approximately $25/s generated - Industrial electricity: $0.03/MJ - $0.10/kWh :::success Upper bound on electricity consumed: 900 MJ/s = 900 MW ::: ### Estimating Energy Usage: Bottom-up - Best claimed efficiency: 1 GHz/W - Network hash rate: 150,000,00 GHz - (excludes cooling, embodied energy) :::success Lower bound on electricity consumed: 150 MW ::: ### Data Furnaces - **Observation:** in the limit, computing devices produce heat almost as well as electric heaters - Why not install mining rigs as home heaters? - Challenges - Ownership/maintenance model - Gas heaters still at least 10x more efficient - What happens in summer? ### Open Questions - Will Bitcoin drive out electricty subsidies - Will Bitcoin require guarding power outlets? - Can we make a currency with no proof-of-work?