The power balance and conditions of co-existing radiative and non-radiative surface plasmon resonance modes have been exploited at the metal film-water interface. Angular (AIM) and wavelength (WIM) interrogation sensing conditions were applied. Polycrystalline, void-free metal layers were sputter deposited, composed of nm-sized crystalline grains. Radiative decay of propagating SPs, with emission into the upper half-space, has been observed for 50-nm thin Au and Ag-layers on BK7 glass and polymeric substrates in the AIM. The associated thermo-optical power budget has been quantified by calorimetric heat flow recordings, comprising a micro-fluidic set-up. For the Au-water interface, at least 88 ± 4 % of the SP-absorbed optical power dissipates by phonon excitation, followed by heat transfer from the metal film into the adjacent liquid phase. Only a small fraction of 2.4 ± 0.6 % dissipates through radiative emission. In presence of a rough interface and WIM conditions, radiative SP-decay persists by emission into the lower half-space. The luminescence type feature most likely originates from radiative excitation and decay of localized SPs, coupled to propagating SPs within the film volume. The spectral characteristic is in accord with earlier reported experimental observations by others and numerical simulations.