The growth and conglomeration of cities in the past century has caused an increase in the intensity and impact of Urban Heat Island (UHI), changing the micro-climate of cities. This impacts the energy consumption of buildings by reducing heating and increasing cooling loads. This paper studies the impact of the urban heat island on the typical buildings in the Phoenix Metropolitan region through an annual energy simulation process spanning through the years 1950 to 2005. The commercial reference building models from the Department of Energy have been used to simulate commercial building stock. The analysis aims to show the impact of the 'atmospheric canopy layer' - UHI that causes an increase in the summer night time temperatures. This study also shows the disparity in results of annual simulations run utilizing TMY weather files, to that of annual recorded weather data. The climate change future weather files created by Intergovernmental Panel on Climate Change (IPCC) are also used to run simulations, and analyzed for the existence of the influence of UHI in such weather-files.