From above the thermal energy content of 14.2 kg LPG is 194.1 kWh. Therefore 194.1kWh
energy is contained in one cylinder of 14.2 kg LPG which costs Rs. 1,1003. Therefore 1 kWh of
thermal energy of LPG cost Rs. 5.67. So, comparing with LPG the generation of 3.0 m3 or 16.68 kWh
the biogas could save Rs. 92.74 per day. Table 1 shows the cost estimation of LPG in terms of
cooking gas. The simple payback period was found to be 2 years.