The AHF (Active Harmonic Filter) will have a loss of approx. 40 to 50Watts per Amps.
Fot 50A, AHF the loss will be approx. 2kW to 2.5kW.
Yes, by adding AHF the kWH consumption will increase in the system, but the main reason for adding AHF if to improve the quality of power. The AHF is always promoted as Power Quality improving equipment and not as energy saving device.
Having said that, there are lot more benefits of filtering harmonic. In many cases where Induction motors are used in the network having higher harmonic levels, the AHF will reduce the energy consumption in motors due to reduced negative sequence harmonic.
Hope above answers your query.