With the intention of developing an electrostatic precipitator (ESP) for small-scaled biomass boilers, several laboratory and field tests were carried out to transfer the theoretical design criteria and approaches into practice. The precipitator can be applied both, as a direct integrated version or as an adaptive precipitation box. Another main aim was the application of alternative fuels. The approaches, ESP design criteria, and the different setups which were used during the development are described. The obtained field test results for standard and alternative biomass fuels are discussed and compared to theory. In addition, physical and chemical analyses of the precipitated filter ashes were performed.