As a general rule, machines manuf in N.A. tend to be designed for one (domestic) voltage, but any that are either European or Asian origin, especially from Japan such as Mazak, Fanuc, Mitsubishi etc, tend to have internal transformers for secondary voltage tuning, in Japan, the common control voltages are 100vac and 200vac, so often the internal controls run on this voltage.
Consumption is based on Watts, this is a product of Amperage and Voltage, If you were running on the high voltage side previously, your bill should should actually be lower if anything, as your load demand has not changed but in your case if you dropped the voltage, therefore the product should be lower.
In any case if the problem is cured, it will be worth it.
Al.