Pakistan, alongside other developing countries, is struggling to understand, plan and realize the energy-environment-economic nexus. In this study, we develop a national-scale bottom-up energy optimization model (Pak-TIMES) employing ANSWER-TIMES modeling framework which provides insight into this nexus for Pakistan. The reference energy system of Pak-TIMES model provides energy demand, supply, cost of energy and GHGs emissions. In total, five supply side scenarios enacted in this study are BAU (Business As Usual), RE-30 (30% renewables), RE-40 (40% renewables), Coal-30 (30% Coal) and Coal-40 (40% Coal) for the period 2015-2035. The results suggest that the cumulative investment cost incurred will be 170 billion USD to meet the electricity demand (3091 PJ) by 2035 with 181.5 million tons of GHGs emission in the BAU scenario. The most environmentally ambitious pathway, the RE-40 scenario will require 179.2 billion USD for investment with 96.0 million tons of GHGs emission. The Coal-40 scenario will cause the highest amount of GHGs emissions, i.e., 338.9 million tons with an estimated investment cost of 184.8 billion USD. Based on the results of this study, PAK-TIMES model, it is recommended that government needs to invest in renewables; given that, the environmental cost of non-renewable energy solutions is significantly higher.