In the photochemical conversion of hydrogen peroxide (H2O2) into radical ·OH, the rule of radiation dose (the quantum yield) on the oxidation kinetics is well known. In contrast, the H2O2 dose mostly remains an attempt-and-error variable. Here, we propose a method to estimate the efficiency of H2O2 dose consumption by the mineralization micro-kinetics that enables a generalist strategy for a more cost-effective dose of the oxidant. It needs the time-dependent H2O2, micropollutant, and product (CO2) measure. Photo-Fenton (FP) hydrochlorothiazide (HCT) oxidation using a tubular photo-reactor and UVA radiation assisted in demonstrating the method. The average value of ~ 38% was on top of the best efficiencies associated with some of the fastest mineralization rates. Such efficiencies depend on the stochiometric concentration of the oxidant. Here, the variable stoichiometric H2O2 excess for mineralization is proposed as a universal metric to quantify the (under-) over-dose of H2O2. Overall, H2O2 excess between 2 and 5 leads to H2O2 consumption efficiencies above 30%, together with a fast rate of CO2 formation (mineralization). In contrast, any value below one invariably leads to a sluggish oxidation rate, leading even to the total depletion of the oxidant. Besides proposing a selection criterion for the most cost-effective H2O2-dose and providing some examples, this work carefully analyzes the commitment of the H2O2 excess concerning the energy costs (EEO).