Plasmon-resonant nanoparticles are being integrated into a variety of actuators and sensors due to their extraordinary optical capabilities. We show a continuum energy balance accurately describes thermal dynamics and equilibrium temperatures in plasmon-resonant nanoparticle systems. Analysis of 18 data sets in which temperature increased ≤10.6 ºC yielded a mean value of R2 >0.99. The largest single relative temperature error was 1.11 %. A characteristic temperature was introduced into a linear driving force approximation for radiative heat transfer in the continuum energy description to simplify parameter estimation. The maximum percent error of the linearized description rose to 1.5 % for the 18 sets. Comparing the two descriptions at simulated temperature increases up to 76.6 ºC gave maximum relative errors ≤7.16 %. These results indicate the energy balance and its linearized approximation are applicable to characterize dynamic and equilibrium temperatures for sensors and actuators in microfluidic and lab-on-chip systems over a broad range of heat-transfer lengths, power inputs and corresponding temperature increases.