It’s so easy to replace 400W metal halide high bay by 100W LED.
First we look at the parameters of the two lamps.
100W LED round high bay: 174 lumen per watt
Luminous flux (Luminaire): 17359lm
400W metal halide high bay:
Luminous flux (Luminaire): 19540 lm
Luminous flux (Lamps): 32000 lm
Luminaire Wattage: 372.0 W
Next we use Dialux to do a simulation analysis.
We can see that the illuminance of the two lamps is very close by simulation. That is why 100 watt LED round high bay is a replacement for 400W metal halide high bay.