The objective of this study is to conduct a cost/effectiveness analysis of the computation of reference evapotranspiration (ETo) in the peninsular of Florida. A meteorological station on the Fort Meade Mine in Polk County, Florida was used to provide data for the calculation of ETo. Five ETo equations were tested to determine the accuracy and cost/effectiveness to the fully measured ASCE Penman-Monteith (Full ASCE-PM) equation on daily, monthly, and annually time steps. The ETo equations ranged in amounts of parameters from the Full ASCE-PM to the Hargreaves. The energy terms accounted for approximately 90% of the total ETo flux. Solar radiation alone also accounted for approximately 90% of the total ETo flux. The highest cost-effectiveness ratios were equations that were able to accurately estimate values without relying on expensive meteorological equipment and/or omitted terms that had a lesser influence on the magnitude of ETo. The seasonal variability in the climate and consequently the emphasis of each meteorological parameter on ETo will create seasonal errors in the reduced sets of the ETo equations. Large seasonal errors were associated with temperature based ETo equations, while solar radiation based ETo equations accurately preserved the seasonal trends. At least in Florida, solar radiation is the key driving force in both the magnitude and the seasonality of ETo.