The Responsible Data Center Siting Act of 2026 directs the Secretary of Energy to develop best practices guidelines for where data centers should be built across the country. The Secretary must consult with the Federal Energy Regulatory Commission, the Department of Defense, and other relevant agencies, and must consider factors including impacts on the electric grid and electricity prices, water availability and quality, local air quality and ecosystems, effects on surrounding communities including noise and visual impacts, national security implications, job creation, and local tax revenue. The guidelines must identify site characteristics that minimize negative impacts and provide a list of ideal locations for data center construction. The Department of Energy must publish the initial best practices within one year of the law's enactment and update them at least every two years thereafter. This legislation affects data center companies, local communities near potential sites, and utilities managing the nation's power infrastructure.