How It Works — High-Efficiency Gas Storage Water Heaters
High-efficiency gas storage water heaters employ the same technology as standard gas storage water heaters: a glass-lined steel tank is heated by a burner located at the bottom of the tank. But a few basic changes make them operate more efficiently. Many ENERGY STAR certified models simply have better insulation, heat traps, and more efficient burners, improvements that have a modest impact on price lead to 8% less energy use. Some very high efficiency models use a secondary heat exchanger that extracts more heat from the combustion gas, cooling it to the point where there is condensation– hence these types of heaters are called “gas condensing.” These gas condensing water heaters, like gas condensing furnaces, require venting through a vertical PVC pipe and a condensate drain.