The energy efficiency, greenhouse gas (GHG) emissions and carbon efficiency of rice paddy production were analyzed in Sari, Mazandaran province of Iran during 2011-2012. Data were collected through questionnaire and interview with paddy producers. The results showed that the net energy gain was 27932 MJ ha-1 and energy efficiency was 1.83 during production. The results of Cobb-Douglas (CD) model showed that the energy inputs of machinery, diesel fuel, chemical fertilizers, and biocides had positive impacts on yield, while seed and human labor were negative. For 1 MJ increase in energy input, the input of seed, labor, machinery, diesel fuel, chemical fertilizers and biocides, yield were changed 0.058, 0.992, 0.078, 0.004, 0.027, and 0.089 kg, respectively. Energy input of machinery with high beta coefficient (0.64) had the most impact on crop yield (p≤0.01). The total GHG emission for paddy production was determined to be 1936 kgCO2eq ha-1 with diesel fuel and machinery having the greatest contributions. The carbon efficiency was estimated to be 4.01.

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