A primary finding of this review of O&M cost is the large variability in O&M cost fraction. Sources from industry (e.g. Sanyal (2004; 2007), Ormat (2020a), and Calpine (2020)) are rare and difficult to interpret due to lack of documentation and resolution. Larger, bottom-up analyses (e.g. GETEM, NETL) have increased transparency, but leave in question their validity by only promising that they are providing realistic values. Thus, in genGEO, we cautiously apply more weight to the industry-derived values and estimate from this meta-analysis that an appropriate O&M cost fraction is within the range of 4.5% to 6.5% (Equation S61).