This review aims to present a summary of the current state of art in applications incorporating thermoelectric generator (TEG) units. Description of components critical to TEG system analysis will be provided. Especially practical results available from testing of the experimental systems will be addressed. The review is split in 2 parts, with first part covering TEG fundamental operating principles and materials, the power electronic converters of the TEG loading system, with applications of domestic boilers and biomass stoves. Second part of the review will provide overview of the solar energy harvesting TEG applications.