In this communication, various planar multiple resonators stacked microstrip antennas with differential inputs/outputs for wireless energy harvesting are presented. The antennas are designed for GSM 900 band using thick substrate on low-dielectric constant. The developed antennas are fabricated on two different substrates to study and compare the efficiency of complete differential RF energy harvesting system. Gain of 9.03, 10.5, 10.62, and 12.05 is achieved for a broad bandwidth of 12, 17.5, 17.9, and 20.2% respectively for various antenna prototypes. Measured results show a peak efficiency of 70.85, 72.49, 75.68, and 86.33% for a load of 2, 1.2, 0.98, and 0.52 kΩ respectively. Finally, wireless power transmission is estimated using link budget analysis.