This paper investigates strategies for managing costs in low-CO2 renewable energy (RE) projects, with a focus on enhancing investment efficiency. The study develops a novel mixed-method framework that integrates Shapley rates, TOPSIS, and Pythagorean fuzzy (PF) DEMATEL to identify effective cost-control tactics. Data is sourced from financial reports, project records, and expert evaluations involving three managers from the energy sector with over two decades of experience in renewable energy investments and CO2 emission reduction. The framework's precision is tested through the VIKOR technique and sensitivity analysis, using five scenarios where the weighting outcomes of criteria are adjusted. Findings reveal that solar energy consistently offers the most cost-effective solutions, while consumer prioritization significantly improves the viability of wind energy investments. The results also emphasize the importance of workforce development in solar energy projects and collaborative cost-control strategies to enhance project success. The study recommends that investors focus on high- or low-level collaborative approaches for solar energy due to its lower associated costs compared to other options. These insights can guide policymakers and investors in optimizing renewable energy investments and enhancing collaboration to reduce CO2 emissions.