In 2004, the total installed capacity of geothermal plants located in 24 countries of the world still amounted to 8.91 GW with an annual power generation of 56.8 TWh; in 2009, these indices grew up to 10.71 GW and 67.2 TWh, respectively; in 2014 these indices reached 12.64 GW and 73.55 TWh (Erdlac et al. 2006; Bertani 2015; Shulyupin and Chernev 2015). Details of installed capacity distribution over the world and development trends were reported by Gehringer and Loksha (2012). In the same period, the annual electricity generation based on geothermal energy increased from 56.8 to 73.55 TWh. In recent years, geothermal energy use was growing most rapidly in Kenya (+ 392 MW), USA (+ 352 MW), Turkey (+ 306 MW), New Zealand (+ 243 MW),