The HiDRA instantaneous condensing water heater from Patterson-Kelley offers up to 97 percent efficiency. With a fire tube design and equipped with the NURO control system, it is available in 800 MBtu and 1,000 MBtu configurations. Its compact design makes suitable for domestic hot-water retrofits or new construction projects, specifically for hospitals, hotels, schools and universities. 877-728-5351; www.harscopk.com.