The Rheem XG40S12HE38U0 is a high-efficiency 40-gallon short natural gas water heater from Rheem’s Performance Platinum series. Designed for compact installations, it delivers robust performance with a 38,000 BTU input while maintaining energy efficiency (approximately 0.62 Energy Factor). Equipped with a self-powered diagnostic gas control valve, a maintenance-free low-NOx burner with self-cleaning capability, and a premium-grade anode rod for enhanced tank longevity. Its eco-conscious design ensures compliance with emission standards (40 ng/J), and it’s rated for high-altitude installations up to 10,200 ft. The model is backed by a 12-year limited warranty on tank and parts and includes a 3-year in-home labor warranty, offering both efficiency and long-term peace of mind.