The JXi heater sets a new standard in pool and spa heating technology with its ultra-compact size, lightweight design and installation flexibility. Ultra-compact, 2'x2' footprint for small spaces, weighs less than 126 pounds unpackaged, best retrofit option, 83% thermal efficiency rating and low-NOx design surpasses strict DOE energy-efficiency requirements. VersaFlo Integrated Bypass technology installed from the factory. Offers up to 20% additional energy savings, automation actuation of flow bypass valve is based on call for heat, and header integration means no external plumbing modifications are needed.