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After all, those bulky storage tanks are almost universally used and thus are viewed as the logical replacement option, especially if the homeowner waits until the storage tank breaks down and leaks all over the floor, so there is no more hot water.
But when homeowners understand how tankless technology works, how easily it can replace conventional storage-type water heaters, and how the Southeast's more moderate climate can support stronger, less costly performance, the decision becomes much clearer.
Tankless water heaters are designed to heat water on demand instead of storing — and reheating — gallons of hot water 24/7/365. This means they provide continuous hot water, though not instantaneous. Without a recirculation system, homeowners may still wait a few seconds for hot water to travel from the unit to the faucet or shower, especially if the tankless system is installed in the same location as the old tank. But once hot water arrives, a properly sized tankless unit can deliver ample supplies of hot water at the desired temperature for as long as the household needs it.
That on-demand difference is central to understanding the value of tankless technology. Instead of thinking about hot water in terms of tank capacity, homeowners should think about how and when their household uses hot water. For Southeast homeowners in particular, factors such as groundwater temperature, installation location, and occasional freeze protection will influence how a tankless system performs. Those same considerations are also useful for homeowners in other regions, where colder incoming water temperatures may affect product sizing.
For Southeast homeowners, the first question is often whether tankless can truly keep up with household demand. The answer is yes… as long as the system is sized properly. A tankless water heater can replace a 40-gallon tank, but the size of the old tank is not the most important factor. What matters more is the home's peak hot-water usage, or how much hot water the household may need at once.
For example, a three-bathroom home does not automatically need the largest tankless model available. The real question is whether all three bathrooms are likely to be used at the same time, or whether the household is more likely to run two showers, a kitchen sink, laundry or even a dishwasher at the same time.
In short, sizing a tankless water heater comes down to two main factors: the home's temperature rise and its peak flow rate.
Temperature rise is the difference between the incoming winter groundwater temperature and the desired hot water temperature, which is typically 120°F. The formula is simple: the desired temperature minus the incoming groundwater temperature equals the temperature rise.
For example, if the incoming water temperature is 50°F, the calculation would look like this:
120°F − 50°F = 70°F temperature rise
Peak flow rate is the maximum hot water a home may need at any given time, measured in gallons per minute (GPM). For example, if a household expects to run two showers and a kitchen sink faucet simultaneously, the calculation would look like this:
2 showers' flow rate + 1 kitchen sink flow rate = total peak flow rate
Most homeowners rely on a professional installer to size their water heaters, but tools like Noritz's residential sizing calculator can serve as a helpful starting point for research. The tool provides a quick recommendation based on zip code and appliance use, helping homeowners better understand their options before discussing the project with an installer or contractor.
When choosing a tankless system, the selected unit should meet or exceed both the home's maximum temperature rise (the coldest season of the year) and its peak flow rate, since an undersized unit may struggle when multiple fixtures are running at once or when water temperatures drop to their lowest point.
Because the temperature rise depends partly on incoming groundwater temperature, the Southeast has a strong advantage: its warmer groundwater usually means a tankless unit does not have to work as hard to raise the water temperature to the desired set point. In many cases, a smaller unit may meet the needs of a Southeast home versus a home in a colder region.
For example, an EZ98 with a maximum input of 180,000 BTU may meet the needs of a three-bathroom home in the Southeast. Meanwhile, the same-sized home in the Northeast may require a larger model, such as the EZ111 with a maximum input of 199,000 BTU.
(Note: "BTU" stands for "British Thermal Unit," a measure of the heat energy needed to raise the temperature of the water. One BTU represents the heat needed to raise one pound of water by 1°Fahrenheit.)
The advantage of a smaller — and, therefore, less costly to buy and operate — water heater makes tankless an important option for Southeast homeowners to consider. Tankless water heaters are not just for colder regions or homeowners seeking a premium upgrade. In warmer climates, tankless technology can be a practical replacement option because the incoming warmer water temperature requires less energy to deliver the desired hot water output.
The Southeast climate may also offer greater installation flexibility. In areas where the winters are milder, homeowners can install a tankless unit outdoors, freeing up space inside the home or the garage.
Outdoor installation should still account for the possibility, however remote, of freezing weather. Built-in freeze prevention can help during mild cold snaps, but it requires electrical power. If freezing weather results in a power outage for any length of time, the best way to protect a tankless unit is to shut off the hot and cold isolation valves and drain it.
Installation expense is, of course, another understandable concern. Costs vary because every home and installer is different, but labor and materials are often a significant part of the final price. Noritz offers EZ Tank Replacement packages (EZTR40, EZTR50, and EZTR75) designed to replace conventional 40-, 50-, and 75-gallon tank models. This simple replacement assumes, of course, that the previous tank met the home's hot water needs.
These replacement packages include truly unique features such as:
Homeowners may also wonder whether their new tankless, gas-fired water heater requires a larger gas line or major electrical upgrades. A standard ¾-inch gas line is not always required, but line sizing depends on the gas pressure, gas line length, and the maximum BTU rating of the tankless unit. As for electrical consumption, Noritz tankless units operate on standard 120-volt power and consume 5 amps or less.
For many homeowners, the long-term benefits of tankless water heating can be compelling. Because a tankless water heater heats water only when it's needed, homeowners typically see lower gas bills. With proper installation and maintenance, a tankless unit should also last 15–25 years, as reflected in Noritz's industry-leading 25-year warranty on its dual stainless-steel heat exchangers.
Maintenance should still be part of the ownership plan. One common misconception is that tankless water heaters do not need regular maintenance. But like an air conditioner or gas furnace, they should be inspected, flushed (see below), and otherwise maintained yearly. For example, homeowners should keep the unit clean and free of dust, lint, and other debris that could affect performance.
Water quality also matters. In areas with hard water, minerals such as calcium, magnesium, and manganese can build up inside plumbing and water-heating equipment over time, reducing efficiency and potentially shortening the life of the system. Homeowners can check local water hardness maps for a general idea of their area's water quality, but a simple water test can provide a more accurate answer. Depending on water hardness, descaling may be needed every one to three years, or more often if recommended by a professional. (See: "How to descale a Noritz tankless water heater.")
For Southeast homeowners, tankless water heaters deserve a closer look. The region's warmer groundwater temperatures can support strong performance, while Noritz solutions, such as residential sizing tools and EZ Tank Replacement packages, can help homeowners better understand and simplify the switch from tank models.
Whether the home is in the Southeast, Northeast, Far West, or anywhere in between, the right tankless system starts with proper sizing, professional installation, and routine maintenance.