Shared autonomous electric vehicles (SAEV) represent a transformative shift in urban mobility, promising enhanced flexibility, sustainability. This study investigates the impact of integrating SAEVs into a taxi-hailing aggregator, focusing on their operational efficiency and environmental benefits. Based on New York City trip data from high-volume for-hire vehicle services, a simulation is conducted to model how such vehicles would operate, exploring fleet performance, CO2 emissions, and revenue while considering constraints such as charging infrastructure, fleet size, and real-time demand fluctuations in an urban setting. The simulation evaluates key metrics, including CO2 emissions, time to pickup, lost trips rate, and net revenue, comparing them with traditional driver-based taxis. The primary results confirm expectations: initially, SAEVs operate with similar efficiency to traditional taxis due to charging constraints under limited fleet size that cannot fully meet demand. However, as the fleet size expands, missed rides decrease more rapidly for SAEVs, as they operate continuously, unlike traditional taxis, which have service gaps at night.