Experimental tests were carried out in three geometrically similar laboratory-scale wire-plate electrostatic precipitators in order to evaluate the best electric parameter for scaling the equipment. The parameters kept constant were the pseudo-homogeneous electric field, E p , the current density, j, the dimensionless voltage, U 0 , and the power consumption per unit collection area, P A . The experimental tests consisted in measuring the overall efficiency of particle removal, which was used as the comparison parameter. The results indicated that, for constant U 0 , efficiency increased with precipitator size. As for the parameters E p and P A , the data were scattered and showed no clear tendency. Finally, by keeping j constant, the overall efficiency of the precipitator remained constant (within AE 5%), regardless of the precipitator size. Precipitator efficiency increased exponentially with increase in power consumption per unit gas volume, and all data were well fitted to a power law correlation.