A method to analyze the heat generation in luminescent barium borate glasses under continuous optical excitation is presented. The heat development is monitored by infrared thermography. Experimental surface temperature data are used as input for the differential heat equation to evaluate the volumetric heat rate from the spatial and temporal development of the temperature distribution. Having determined the volumetric heat rate in the glass, the heat generation under optical excitation can be estimated without further knowledge of optical parameters. Experiments on barium borate glasses with different doping levels are performed. For comparison, the heat generation is also estimated on the basis of optical parameters only to confirm the accuracy and validity of the presented method via infrared thermography. The experimentally determined total heat generation is in good agreement with those calculated from optical properties.