Which energy sources can conventional storage water heaters use?

• A. Natural gas, Propane, or Electric
• B. Solar energy only
• C. Wind energy
• D. Geothermal energy

Answer: (A)

Conventional storage water heaters heat water with simple, proven methods: electric resistance elements inside the tank or a gas burner that warms the water. Those two options cover the common energy sources, namely electric, natural gas, or propane. Solar, wind, and geothermal systems aren’t direct energy sources for a standard storage tank heater; solar needs a dedicated solar water-heating setup, wind would require electricity generation first, and geothermal is used in different heating systems rather than a typical tank. So the best answer reflects electric, natural gas, or propane as the viable energy sources for conventional storage water heaters.