The electrical activation of 1× 10 20 cm-3 implanted Al in 4H-SiC has been studied in the temperature range 1500-1950 C by the analysis of the sheet resistance of the Al implanted layers, as measured at room temperature. The minimum annealing time for reaching stationary electrical at fixed annealing temperature has been found. The samples with stationary electrical activation have been used to estimate the thermal activation energy for the electrical activation of the implanted Al.