At 0.99 EF/0.97 UEF, Navien’s NPE-S series condensing tankless water heaters are extremely efficient. They supply maximum inputs from 150,000 to 199,900 Btu/h and efficient outputs from 148,500 to 197,900 Btu/h. Maximum flow rates are from 8.4 to 11.1 gpm. They have 1/2-inch gas pipe capability up to 24 feet, 2-inch PVC venting up to 60 feet, dual stainless steel heat exchangers, field gas convertibility and cascade up to 16 units without an external control box. 800-519-8794; www.tanklessmadesimple.com.