This thesis was undertaken to investigate Analysis of Grid-Tie Resilient PV System with battery back-up as an alternative source of energy to solve the regular grid failure problem in the Ethiotelecom MSAG, Debre Markos Town. The thesis used primary sources, grid failure data from Bahir Dar Ethiopian Electric Utility (EEU), temperature and irradiation level (from meteorological station), secondary sources, develop modeling and simulated Using ardiuno Proteus 8 professional simulation software to conduct the thesis. The results of this work show that the grid connected PV system with battery back-up requires a 48VDC battery bank with a capacity of 1695.3 Ah (C10 rating). The system requires battery inverters / or extender model-XTH 6000-48 with a power rating of 17.125kW AC with a charging current of 100Adc, 92 of the BP 7180 modules and Sun master XL models 3-phase DC to AC solar inverter. The production of electricity from grid connected PV system with battery backup of the Ethiotelecom MSAG, Debre Markos Town is estimated to be about 33.3MWh, which is during the active grid time and grid failure time per year. The value of the benefits of selling energy generated by the system annually at current flat rate price is about 26,306 Birr/year. However, the actual yearly average consumption of the MSAG based on the load data as indicated in table 3.3 (12,926 kWh) is on average around 8,919 Birr/year, and due to solar power generation Ethiotelecom has around 4,711,546 Birr per year benefited and its customers well satisfied.