The primary purpose of the PhD thesis is to estimate and investigate the energy consumed during the production – process of the most well-known cryptocurrencies and those of who occupy the largest market capitalization, such as Bitcoin, Ethereum, and emerging cryptocurrencies such as the Cardano. At the same time, the examination of the existing energy cost estimation methods will be carried out to draw conclusions regarding the correctness(accuracy) of these estimates, as well as differences in energy consumption among the various forms of validation that exist in cryptocurrencies (PoW, PoS, etc.). Finally, the environmental impact of this production (Co2 emissions, E-waste) will be also investigated.