Replacing an old water heater with a tankless model is generally worth it if you want endless hot water, a longer lifespan (15–20 years), and space savings. However, it comes with a higher upfront cost ($2,400 on average) and requires annual maintenance, making it best for homes with lower hot water demands.
Because tankless water heaters are more efficient, they cost less money to operate. This can save you money in the long run since utility bills are lower than with a tank water heater. Many people find that the cost savings in energy usage eventually makes up for the higher initial cost of a tankless heater.
The primary drawbacks of tankless water heaters are their significantly higher upfront purchase and installation costs, restricted flow rates that can struggle to supply multiple high-demand fixtures simultaneously, and mandatory annual maintenance to prevent scaling.
In freezing temperatures, condensate produced by a condensing tankless hot water heater can freeze inside the drain line, which can cause leakage, operation issues or shutoff. To help keep your indoor tankless water heater from freezing, use a direct vent exhaust & intake system.
As temps drop, the risk of having frozen pipes in your home increases. Typical high-risk areas for freezing include pipes within exterior walls, as well as exposed pipes that run through unheated or uninsulated areas such as attics or basements.
Yes, you should drip both hot AND cold. Otherwise, the area inside the tankless water heater between the cold water line and the heating element can freeze up and burst (happened to me in 2021 freeze). If you drip both slowly, it ensures all water is running through all the lines.
Plumbers often hesitate to recommend tankless water heaters because they act like high-performance sports cars. Unlike traditional tank models that are "workhorses" and can function while mostly ignored, tankless units require precise installation, regular maintenance, and are highly sensitive to mineral buildup.
For larger households, multiple showers, laundry, and dishwashing may run at the same time. Hot water demand could reach 10–12+ GPM. A high-capacity tankless water heater—or even two units installed in parallel—may be the best solution.
Here are some common reasons why your tankless water heater might not be working and how you can troubleshoot these problems.
A propane tankless water heater typically uses 1 to 3 gallons of propane per day, which translates to about 30 to 90 gallons per month for an average household.
A 10-minute shower typically uses 12 to 25 gallons of hot water, depending on your showerhead's flow rate and how hot you keep the water.
100-Pound Tanks
If you do not have your 100-pound tank filled on-site, it needs to be 3 feet from all building openings and 5 feet away from any ignition source, direct vent intakes and mechanical air intakes.
Tankless water heater installation costs between $1,404 and $3,899 for your home, depending on unit size and setup. The fuel type you choose shapes your upfront and utility costs, with electric lower-priced and solar earning tax credits.
This problem usually comes down to capacity, heat production, or mixing issues inside your plumbing system. Sometimes the fix is simple, like adjusting your water heater temperature or flushing out sediment. Other times you may need a new mixing valve, an element replacement, or a different size water heater.
You can see that, in a typical gas system, a tankless water heater with a capacity of 199,900 BTU will require a 1-inch pipe size for a 20 ft branch length (based on the 0.3 in w.c. pressure drop in Table 2). The same appliance would require just a ½” pipe size based on Table 4 the 3.0 in w.c. pressure drop.
Insulate your tankless water heater pipes to prevent freezing and bursts. When plumbing guides talk about “insulating your tankless”, they mean the pipes going to and from your unit. They're as susceptible to freezing and bursting as any other pipes in your plumbing system.
A tankless water heater usually goes cold mid-shower because the water flow drops below the heater's minimum activation threshold, or the system is overloaded by using too many fixtures at once. It can also happen if sediment blocks the filter or the unit is improperly sized.
Tankless water heaters come with a limited flow rate, meaning they might struggle to provide hot water simultaneously to multiple appliances or fixtures. If your household comprises several individuals taking showers or running appliances concurrently, you may need to invest in a larger unit.
Plumbers often hesitate to recommend tankless water heaters because they act like high-performance sports cars. Unlike traditional tank models that are "workhorses" and can function while mostly ignored, tankless units require precise installation, regular maintenance, and are highly sensitive to mineral buildup.
Yes, a tankless water heater can fill a bathtub. Because tankless systems heat water on demand, they provide a continuous stream of hot water, which prevents you from running out halfway through filling a large soaking tub.
For a 3-bathroom home, you generally need a tankless water heater with a flow rate of 7 to 9 GPM (Gallons Per Minute). This size can effectively run 2 to 3 major hot water fixtures (such as a shower and a washing machine) simultaneously.
The answer is no — tankless water heaters can save money on your monthly electric bill because they're 8%-34% more efficient than storage water heaters.
Installing a tankless water heater through Home Depot typically costs between $𝟐,𝟒𝟎𝟎 and $𝟓,𝟒𝟎𝟎 in total, including both the new unit and professional labor.
Here is a simple way to decide: Choose Navien if you want the highest efficiency, longest warranty, and built-in recirculation. Choose Rinnai if you have a large household and need the highest flow rates. Choose Rheem if you want a reliable brand at a lower price point.