Grand Hall Eternal Hybrid Water Heating System Eternal Hybrid water heating combines the benefits of a tank water heater and a tankless into one super-efficient unit. Rather than a single-pass heat exchange that Grand Hall says can waste heat, the Eternal Hybrid uses a multipass heat exchanger that drives heat downward and recycles it through 44 stainless steel pipes for maximum efficiency, the maker says; water spreads evenly around the pipes for fast heat absorption. Cold water flows upward to prevent sedimentation buildup. The firm says the counterflow technology allows for faster delivery for multiple applications at once versus a tankless. The unit is half the size of a 50-gallon tank model but provides 300% higher output. The Eternal Hybrid is 86% efficient and generates near-zero greenhouse gas emissions. 877.934.7455. www.eternalwaterheater.com.