Medium Transport
Flight Crew Flight Instructor; Flight Crew Instrument; Flight Crew Multiengine; Flight Crew Air Transport Pilot (ATP)
Flight Crew Last 90 Days 70; Flight Crew Total 6200; Flight Crew Type 500
Situational Awareness; Communication Breakdown
Deviation / Discrepancy - Procedural Published Material / Policy; Ground Event / Encounter Object
Aircraft Aircraft Damaged
Human Factors
I was the Captain flying from ZZZZ. We landed on Runway 10 in ZZZZ at approximately XA47Z. We landed in ZZZZ and taxied to the South ramp to clear customs. After clearing customs; we started the aircraft up and taxied to the North ramp to be parked in position for our outbound fight. While taxiing to the other side of the airport it began to rain. It was raining enough that the wipers were needed to see in front of us.We had a marshaler guiding us into our parking spot. It was one situated in a position where we needed to nose in; and turn 180 degrees to face out.  He instructed us to turn right into the empty spot facing a wall. He then instructed us to turn right again.  As I turned the aircraft to the right (parallel to the wall and the taxiway) Co-pilot noticed the marshaler may have been getting us close to a GPU situated along the wall. Co-pilot asked 'are we clear?' I slowed the plane; basically to a stop to look back as far as I could. From what I saw through the rain covered side window we were clear of the GPU. I then moved my attention the the marshaler who instructed me to turn right yet again to face out (in line; wingtip to wingtip with the other parked planes). It was at that point we felt a slight jolt and realized the wing had come into contact with the GPU.After the impact; I set the brake and the marshaler ran over to the GPU. He was able to push it along the wall away from the aircraft. He then came back to the nose of the plane to finish parking us.After the engines were shut down; and the checklist complete we opened the door to inspect the damage. There was a dent in the slat; and part of the wingtip due to the collision.In the future I will use more caution when trying to maneuver the aircraft on a congested ramp. Looking back; it would have been a good idea to request a wing walker as well.
Medium Transport aircraft Captain reported making contact with a Ground Power Unit while being marshaled in to their parking spot.