This paper presents a reconfigurable wide input power range radio frequency (RF) energy harvester (EH) with alliance for wireless power (A4WP) wireless power receiver (WPR). A reconfigurable RF-DC converter for RF EH and maximum power point tracking algorithm are proposed to maintain high efficiency over a wide input power range -20 to +20 dBm. The A4WP WPR is designed and merged with the EH to receive power higher than +20 dBm. In order to improve the power conversion efficiency (PCE), the delay between the ac input voltage and current is compensated by the proposed open-loop delay compensation method. The chip is implemented in 0.18 μm bipolar-CMOS-double-diffused metal-oxide-semiconductor process. The die area of the chip is 4.3 mm × 3.2 mm, including the pads. The proposed EH with WPR achieves a measured peak PCE of 48.19% with respect to the input power of 0 dBm at 900 MHz. It also has a peak PCE of 82.14% with respect to the input power of 30 dBm in an A4WP mode operation at 6.78 MHz.