Dissertation (MSc Biodiversity Conservation)The efficiency of energy sources used by households was experimentally determined in this study. To achieve the study objectives, comparison was done between different energy sources such as LPG, electricity, charcoal and firewood. The comparison was determined by observing efficiency of energy sources and the subsequent cost. The tools like experimentation, questionnaire, interviews, and documentary data were used. Four types of energy sources were employed to cook 250g of beans. These energy sources include LPG, electricity, charcoal and firewood. The reported Mean (and Standard Error) of time used in minutes were 121.2 ± 0.12, 135 ± 0.12, 137.4 ± 10.2, 182.4 ± 0.42 for LPG, electricity, charcoal and firewood, respectively. Statistically the results revealed that there was a significant difference in time used to cook 250g of beans among the energy sources (F = 232.26, df = 3, P < 0.001). Furthermore, the results showed that there was a difference in cost associated with cooking of 250g of beans whereby the cost is Tanzania shillings, 1711/= (55%) for LPG, 643.47/= (21%) for electricity, 387.10/= (13%) for charcoal and 347/= (11%) for firewood. In this case the study showed that firewood had less cost compared to LPG, electricity and charcoal. Most of the households in urban Zanzibar rely on biomass fuel (firewood and charcoal) for cooking and heating due to their affordable cost and availability. The subsidy in LPG and electricity as sources of energy that is friendly with the environmental conservation need to be considered. This will reduce the heavy use of charcoal and firewood which affect forests negatively.