  We use Total Solar Irradiance (TSI) measurements from the VIRGO (Variability
of solar IRradiance and Gravity Oscillations) instrument on board SOHO to
obtain preliminary estimates of the mean total radiative energy emitted by
X-class solar flares. The basic tool is that of summed-epoch analysis, which
has also enabled us to detect and partially characterize systematic errors
present in the basic data. We describe these errors, which significantly
degrade the photometry at high frequencies. We find the ratio of GOES 1-8\{AA}
luminosity to total bolometric luminosity to be of order 0.01.
