PA31 pilot reports electrical fumes during taxi out and returns to ramp after turning off nonessential electrical equipment. Source of fumes cannot be located.

Narrative

After departing ramp; we were taxiing for takeoff from Runway 27R. After joining Taxiway L we began smelling what appeared to be electrical smoke in the cabin. The initial indications of smoke were between L3 and L4. The intensity of the odor was increasing. We began to shut off all non-essential electrical equipment. We immediately contacted Ground and requested to return to the gate. Ground cleared us back to the gate. After returning to the gate; we performed a normal aircraft shutdown and talked with the passengers about the situation. They said that they began to smell smoke after we had turned around and were on Taxiway M. We deplaned the passengers and inspected the aircraft. We checked all of the CBs and none were popped. We were not able to determine the source of the smoke. We called Dispatch to let them know why we returned to the gate. Dispatch and reservations arranged for the passengers to be transported to ZZZ1 on a transportation van. After talking with Dispatch and Maintenance; we were told to taxi the aircraft to the GA ramp; and leave the aircraft for Maintenance. I am reporting this because; in retrospect; I could have handled the situation a little differently. 1) I should have had the fire trucks meet us at the gate. But because the smoke seemed to decrease in intensity when we started deactivating non-essential electrical equipment; I chose not to call the fire trucks. 2) I did not fully follow the aircraft's Electrical Emergency Checklist because I felt that it would jeopardize our safety and ability to keep in contact with ZZZ Ground and emergency services if needed. The aircraft's Electrical Emergency Checklist called for disabling the master switch and then turning off all electrical equipment. Then enabling the master switch and reactivating equipment one system at a time to isolate the source of the smoke. I felt that by disabling the electrical system and consequently all aircraft lighting at night; we would have also been in danger of being struck by much larger taxiing aircraft. Additionally our Communication/Navigation Stack was a Garmin 430 and 530. I felt that the time it would have taken that system to boot up from a powerless state would have hindered our ability to contact ATC for emergency services.