Economic equations were developed using life cycle costing (LCC) to systematically investigate the economic feasibility of energy recovery from anaerobically digested wastewater solids. The boundary includes anaerobic digestion (AD), gas pretreatment technologies (GPT), and energy recovery options. Cost functions and average values for unit capital costs and operation and maintenance (O&M) costs were derived from the surveys of over 40 wastewater treatment plants in the U.S. and Canada, vendor quotes, and literature values.The sensitivity of LCCs to input factors were tested, using factorial design. Electricity price and unit O&M costs of AD and GPT were predicted to be the most important factors so good estimates in determining the economic feasibility in terms of LCC are required. Uncertainty and reliability in predicting LCCs were examined, using Monte Carlo simulation. One-stage thermophilic digestion was predicted to be the most economical process due to a shorter SRT.