The US targets net-zero-carbon electricity by 2035, emphasizing the need for both supply- and demand-side strategies in the power sector. Our study focuses on demand-side carbon reduction via load regulation, using real-time greenhouse gas emission data to optimize electricity use without reducing overall consumption. Our multi-scenario analysis indicates significant potential for carbon footprint reduction by adapting strategies to specific grid characteristics. For example, California could have 32.58% more emission reduction with annual instead of quarterly optimization. In grids with diverse generation resources, expanding adjustment ranges from ±5% to ±8% can boost carbon reductions from 1.19% to 1.64%. Our results also reveal low greenhouse gas intensity fluctuation areas as more cost sensitive in electricity consumption than high greenhouse gas intensity fluctuation areas, providing essential insights for policymakers.