Hello Shankar,

There are many factors that go into the energy use for the two options, here
are a few:
- The chilled water plant will have condenser pumps, a cooling tower and
chilled water pumps that need to be factored in. If your VRF system is
air-cooled it will not have those pieces of equipment.
- VRF systems have variable capacity compressors with good part load
efficiency, your chiller may not have good part load performance.
- On the system level, VRF systems have fan-coil units with small ECM motors
while your chilled water plant may be connected to a VAV system with large
fans. - Ventilation for VRF systems is typically through dedicated outdoor
air units with heat recovery while VAV systems typically don't have heat
recovery.
- VRF systems often have heat recovery which reduced energy use when there
is simultaneous heating and cooling in the building.

Hope this helps.

Regards,
Aaron

Aaron Smith, P.Eng
M&R Engineering Ltd.