Tankless Water Heater Vs. Standard Storage Tank Water Heater
There are many models of storage water heaters that have varying heating efficiency and recovery times. There are fan blower assisted, heat pumps and tankless/storage hybrids to quickly name just a few; but for this comparison, I am using a gas fueled 160k-199k tankless water heater vs. a 40 to 65-gallon gas-fueled atmospheric storage tank with a flue exhaust.
The main difference initially is the cost upfront. The tankless unit itself will be, in general, 1.5 to 2 times more than the storage tank, whether it is a 40, 50 or 65-gallon storage tank. Secondly, there is more cost to run the gas supply to the tankless because it has a higher gas demand; most 40 to 65-gallon water heaters will have a BTU range of 40k to 55k, whereas the tankless BTU range will be three times higher starting around 160k and going all the way to 199k (which is the most common for a home with three or more bathrooms) to super heat the water as it travels through the tankless heater.
Size and Location
Tankless water heaters are generally half the size of a typical storage tank (with 40 to 65-gallon tanks being the most commonly used) due to the tankless water heater having a heat exchanger the size of a small toaster oven that heats the water vs the entire unit being a storage tank that stores the heated water. Storage water heaters are meant to be installed inside the home away from the harsh weather, primarily rainy and cold weather vs tankless water heaters which are designed to be an interior or exterior installed unit; and that can significantly free up valuable space inside the home. And while storage tanks can be suspended above the floor (more common in a commercial setting than residential), they typically are not because of the additional weight the home’s structure would have to support safely; vs the smaller gas-fueled tankless water heater which can be supported on the wall or in the air safely and easily, weighing in at around 80 pounds.
Maintenance Requirements
Both tankless water heaters and storage water heaters should have a regular maintenance schedule.
Storage tanks and tankless water heaters should have the T&P valve (which is the safety device which, when under excessive pressures of 150 psi or heat within the storage tank exceeds more than 215 degrees, allows a loaded spring inside to open and allows the pressure to escape) replaced every three years, per the manufacturer, to keep the spring in good working order.
Both units should have their expansion tanks checked regularly to verify the pressure of the expansion tank matches the incoming water pressure of the home, and to check to see if the expansion tank has failed or not.
Storage tanks should be completely drained and flushed out regularly, every three years is a good rotation as it aligns with the T&P replacement. When servicing the storage tank, the anode rod (which is the life line of storage tanks because it gives itself sacrificially to the corrosive nature of water and prevents rusting of the water tank) should also be inspected and really just replaced to optimize the protection of the storage tank.
Tankless water heaters in regions that have hard water or if installed in a commercial setting, should flush the units with a food grade descaler and then again with a vinegar/ water solution, and a final clean water rinse.
The interior should be visually inspected for any water leaks or excessive oil from the heat exchanger, check the air vent valve, clean the air intake screen, clean the condensate cap and cold water inlet filter.