As the world becomes increasingly aware of the devastating effects of climate change, national leaders have united to tackle the challenge of decarbonisation. Electricity production, being the highest carbon-intensive industry, has the largest share in global greenhouse gas emissions, making it an essential target for decarbonisation. Replacing fossil fuel-based power generation with non-carbon alternatives such as renewables or nuclear is crucial for deep decarbonisation of the electricity system. However, integrating these technologies is not without challenges. Nuclear plants pose risks such as radiation leaks, while renewables are dependent on the forces of nature and have variable generation. Effective supply-side management strategies are required to overcome these challenges and achieve carbon neutrality by 2040. This paper presents two scenarios developed to study the effectiveness of supply-side solutions in a transitioning electricity system. We have considered Karnataka electricity system ( a state in India) as a base case which is rich in solar, wind and hydro resources endowments. The two scenarios developed are KASTATUSQUO, which assumes the existing supply-mix will continue with new capacity additions during 2019-2040 and, KARENNOTRADE, which assumes full retirement of coal-thermal capacity, zero electricity trade, and new capacity additions in renewable energy sources during 2019-2040. The model results suggest that phased retirement of existing thermal power plants and increased renewable capacity could achieve the goal. However, achieving a closed electricity system with no external transactions or inter-region electricity trade would require an additional investment of Rs. 1029 billion. KARENNOTRADE scenario is environmentally viable as there are no emissions. As the world becomes increasingly aware of the devastating effects of climate change, national leaders have united to tackle the challenge of decarbonisation. Electricity production, being the highest carbon-intensive industry, has the largest share in global greenhouse gas emissions, making it an essential target for decarbonisation. Replacing fossil fuel-based power generation with non-carbon alternatives such as renewables or nuclear is crucial for deep decarbonisation of the electricity system. However, integrating these technologies is not without challenges. Nuclear plants pose risks such as radiation leaks, while renewables are dependent on the forces of nature and have variable generation. Effective supply-side management strategies are required to overcome these challenges and achieve carbon neutrality by 2040. This paper presents two scenarios developed to study the effectiveness of supply-side solutions in a transitioning electricity system. We have considered Karnataka electricity system ( a state in India) as a base case which is rich in solar, wind and hydro resources endowments. The two scenarios developed are KASTATUSQUO, which assumes the existing supply-mix will continue with new capacity additions during 2019-2040 and, KARENNOTRADE, which assumes full retirement of coal-thermal capacity, zero electricity trade, and new capacity additions in renewable energy sources during 2019-2040. The model results suggest that phased retirement of existing thermal power plants and increased renewable capacity could achieve the goal. However, achieving a closed electricity system with no external transactions or inter-region electricity trade would require an additional investment of Rs. 1029 billion. KARENNOTRADE scenario is environmentally viable as there are no emissions.