Tank vs. Tankless Water Heaters
What are the differences and which is better?
There are pros and cons to each style of water heater
Tankless heaters take up less space and can produce an unlimited supply of hot water. They are energy efficient as there is no standby energy loss. With proper maintenance, they may last longer than traditional tank style heaters. However, they are more expensive and often cost more to install. There are electrical and venting considerations and expensive upgrades may be necessary. Although tankless heaters can deliver unlimited hot water, it is not instantaneous, since the water needs to pass through the exchanger to heat. Also, all the water sitting in the tube since the last usage needs to be delivered first, before the heated water can reach the delivery point. There is also a limit to how much hot water can be delivered at one time.
Traditional tank style heaters can deliver as much hot water as piping allows. Tankless heaters provide a limited flow of hot water per minute, typically 3.5 GPM with an electric unit and 10-11 GPM for gas. ( the average shower uses about 2.5 GPM). When installing a tankless heater, it is important not to undersize the unit. Doing so will not allow hot water to reach more than one source at the same time. Possible solutions to this problem are to install multiple units or a recirculating pump system. However, these solutions increase the costs involved. And as stated above, hard water can destroy tankless heaters. Depending on the manufacturer, the water hardness level should be below 7 grains per gallon. In areas with hard water, like here in Pinellas County and throughout Florida, a water softener may be needed as well.
Overall, electric tankless units work best in low-use households. They work well as point-of-use heaters. They can be effective in boosting existing water heating systems. Natural and propane gas tankless units can produce a higher capacity. They have greater heating ability and are more efficient than electric. With proper sizing, they can be a good choice for whole-house water heating.
Hybrid water heaters are another option. Hybrid water heating units capture heat from the air then transfer it to the water. They are more energy efficient than standard tank type heaters. They are initially more expensive than traditional tank style heaters, but energy savings over time offsets the higher initial cost. Hybrid water heaters do require more space. Because the heat pump is on top, they can require over 7′ floor-to-ceiling clearance, with enough uncooled space around the heater to allow it to capture heat from the air. A condensate drain is required for the discharge.
With any water heater, an expansion tank or device is required per plumbing code. When water is heated, it expands, therefore, check valves keep expanding water from flowing back into the municipal water supply. Most water heaters have little room for heat expansion. The expansion tank receives the expanded water, protecting the heating system. They do not take up much space and are usually installed in the piping at the water heater.