The total energy flux for three different plasma process devices has been measured by means of a simple thermal probe. The procedure is based on the measurement of temporal slope of the substrate temperature during the plasma process. A substrate dummy which is thermally isolated is inserted into the plasma at the substrate position. The thermal probe presented allows for sensitivities of approximately 10(-3) J/s and it can be simply used under typical plasma environments, e.g.: for a-C:H film deposition by magnetron sputtering of a graphite target in Ar/H-2 (#1); in an RF plasma which is used for the modification of micro-disperse powder particles (#2); and nitrogen recombination on metal surfaces in the afterglow of an electron cyclotron resonance (ECR) discharge (#3). Measured specific energy fluxes are 0.03 J/cm(2) s for carbon film deposition and 0.08 J/cm(2) s for sputtering of molybdenum films which are obtained in #1. In #2 the specific energy input is in the range of 0.01 J/cm(2) s, while under the conditions of #3 values of approximately 0.5 J/cm(2) s have been determined. The measured values are compared with the energetic contributions which are calculated on the basis of the relevant plasma parameters.