The study investigates the transduction of visible radiation at resonant frequencies into thermal energy by surface plasmons on gold nanoparticles. The temperature in aqueous suspensions of 20-nanometer gold particles irradiated by a continuous wave Ar+ ion laser at 514 nm increased to a maximum equilibrium value, which was proportional to the incident laser power and nanoparticle concentration at low concentrations. The heat input to the system by nanoparticle transduction equaled the heat flux outward by conduction and radiation at thermal equilibrium. The efficiency of transducing incident resonant light to heat was determined using an energy balance to obtain a microscale heat-transfer time constant from the transient temperature profile. Modulating the incident continuous wave irradiation increased the transduction efficiency from 3.4% to 9.9%. The results support the development of thermofluid systems that incorporate nanoparticles to transduce light to heat, including miniaturized analytical and manufacturing devices.The study investigates the transduction of visible radiation at resonant frequencies into thermal energy by surface plasmons on gold nanoparticles. The temperature in aqueous suspensions of 20-nanometer gold particles irradiated by a continuous wave Ar+ ion laser at 514 nm increased to a maximum equilibrium value, which was proportional to the incident laser power and nanoparticle concentration at low concentrations. The heat input to the system by nanoparticle transduction equaled the heat flux outward by conduction and radiation at thermal equilibrium. The efficiency of transducing incident resonant light to heat was determined using an energy balance to obtain a microscale heat-transfer time constant from the transient temperature profile. Modulating the incident continuous wave irradiation increased the transduction efficiency from 3.4% to 9.9%. The results support the development of thermofluid systems that incorporate nanoparticles to transduce light to heat, including miniaturized analytical and manufacturing devices.