CONVENTIONAL WATER HEATER
Tank-style water heaters (also known as traditional water heaters, standard water heaters, or conventional water heaters) are traditional water heaters that are found in most homes and are used to heat the water used in your home. It’s typically a large cylinder that holds between 30-to-100 gallons of water, with the most common size for homes usually holding about 50 gallons of water. There are also three types of tank-style water heaters: gas, oil, and electric.
POWER VENTED WATER HEATER
A power vent water heater is not hooked up to your home's chimney. A power vent water heater is vented horizontally and vents exhaust through a horizontal pipe that leads out your home. An added fan/blower pushes the exhaust gases through this pipe.
HEAT PUMP WATER HEATER
A heat pump water heater takes heat from one place and moves it to another by compressing and expanding refrigerant. To heat water, the heat pump pulls warmth form the ambient air by compressing the air to increase its temperature. The heat flows through a condenser coil inside the hot water system to transfer heat to the water. Some models have a backup electric heat element to help during periods of high use.