From the article:
ClearSign says its technology also shows a 1 percent thermal efficiency improvement compared to a baseline case with a conventional low NOx burner without flue gas recirculation (FGR). OTSG systems typically operate with FGR to lower NOx emissions. FGR, however, penalizes thermal efficiency, increasing fuel and electricity costs.
ClearSign estimates use of Duplex versus systems operating with FGR will reduce annual operating expense between $90,000 and $100,000.