Economic analysis is an essential evaluation for considering feasibility and viability of large-scale, photoautotrophic algae-based, biofuel production. Thus far, economic analysis has been conducted on a scenario-by-scenario basis which does not allow for cross-comparisons. In 2008, a comparative study was carried out using a cross-section of cost analyses consisting of 12 public studies. The resulting triacylglyceride cost had a spread of two orders of magnitude excluding two studies which were intended for specialty chemicals. The cost spread can be largely attributed to disparate assumptions and uncertainties in economic and process inputs. To address this disparity, four partners from research, academia, and industry collaborated on a harmonization study to estimate algal oil production costs based on a common framework. The updated cost comparison based on a normalized set of input assumptions was found to greatly reduce economic variability, resulting in algal oil production costs ranging from $10.87 gallon(-1) to $13.32 gallon(-1). (C) 2011 Elsevier Ltd. All rights reserved.