Energy Star divides water heaters into five categories. Each type has its advantages and best use applications. Within each category all brands that are Energy Star certified are listed in an Excel spreadsheet which can be downloaded and sort by performance.
A condensing water heater detours the heat exhaust so that it travels a much further distance through the water. Rather than allowing the gas exhaust to exit directly though a chimney in the center of the tank, the exhaust tube is coiled through the water many times thereby heat exchanging the hot air into the water. This is one of the few types of water heater techniques that has gained Energy Star approval.
An air source heat pump (ASHP) is a heating and cooling system that uses outside air as its heat source and heat sink. It differs from a conventional air conditioner in that it can change temperatures in both directions, not just cooling. Energy Star air source heat pumps must provide the highest efficiency production available.
This is a higher efficiency storage water heater that uses better quality components than a standard water heater. It mostly uses a more efficient burner and insulation. It is a viable alternative to other high efficiency water heating techniques because of the competitive cost.
Solar water heaters do not use non-renewable energy sources. So by default it is a very efficient means of heating water. However, in cold climates it can only be used to supplement conventional gas burning water heaters. There are several types of solar water heaters that are outlined on our solar water heating page.
Tankless water heaters have been used in many countries other than the United States of America for many decades. However, they are typically very localized. They are usually mounted directly next to a shower head and only used for that single water outlet. Their energy source is usually either a local propane tank or electricity. Newer more efficient tankless water heaters are wall mounted at a central location in the building, the same as a storage tank water heater. Whole home tankless water heaters supply hot water to all the outlets in the home. They are more efficient because they only heat water when it is needed and don't continuously burn fuel to maintain a certain water temperature. There are several types of tankless water heaters that are outlined on our tankless water heating page.
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