What is negative about a tankless water heater?

Author: Baron Hansen  |  Last update: Saturday, May 23, 2026

Unlike traditional storage water heaters, tankless units may not be able to meet your home's hot water needs if you have multiple outlets running simultaneously. This is because the flow rate of a tankless unit may not be high enough to support multiple uses of hot water at the same time.

Is there a downside to tankless water heaters?

Before you commit to buying a tankless water heater, the primary drawbacks to know include: Higher upfront costs. Tankless water heaters are, on average, quite a bit more expensive to buy and install than tank water heaters. Access to fuel.

What do plumbers think of tankless water heaters?

St Paul Pipeworks plumbers advise against purchasing tankless water heaters from big box stores or online retailers, as homeowners often lack the expertise to determine the correct sizing for their specific needs. Many negative reviews about tankless systems stem from improper sizing or piping installations.

Why don't more people use tankless water heaters?

  • Higher Initial Costs : Tankless systems typically have a higher upfront cost compared to traditional tank water heaters.
  • Installation Complexity : Installing a tankless system can be more complicated, which may require changes to gas lines or electrical systems.
  • Limited Flow Rat

When not to get a tankless water heater?

Electric Tankless Water Heaters

They're less expensive than gas-powered ones but aren't efficient if you run multiple hot water devices. They may struggle to keep up with multiple appliances at the same time.

PROS and CONS of Going From a TANK to TANKLESS Water Heater

Can I replace my 40 gallon water heater with a tankless water heater?

Absolutely! In fact, tankless water heaters are becoming the standard for new home construction because of the energy efficiency.

What is not a benefit of a tankless water heater?

A tankless water heater cannot provide hot water faster than its ability to heat the water. While a tank unit can provide hot water for multiple uses at once, a tankless unit might not be able to support simultaneous usage, such as washing dishes, taking a shower and running a washing machine all at once.

Should I replace my water heater with a tankless?

Tankless water heaters are more efficient and don't experience standby heat loss. This can be especially cost effective if you travel a lot. Some tankless water heater units come with a federal tax rebate. You can get up to $300 off installation!

Can multiple people shower at the same time with a tankless water heater?

A: Yes, but depending on the wattage of your unit, and the temperature you set, the pressure may go down.

What's the best hot water heater to buy?

5 Water Heaters You Can Count on, According to Testing
  • Best Overall. A.O. Smith Signature 900 Smart Electric Water Heater With Hybrid Heat Pump. Read more.
  • Best Value. Rheem 50 Gallon Natural Gas Water Heater. Read more.
  • Best Tankless. A.O. Smith Signature Series Tankless Water Heater with Scale Prevention. Read more.

Is there an IRS tax credit for a tankless water heater?

The federal tax credit for tankless water heaters in 2024 is an excellent opportunity for homeowners to save money while investing in energy-efficient water heating solutions. This tax credit is effective from January 1, 2023, to December 31, 2032.

Where should a tankless water heater not be installed?

Keep your water heater away from outside elements

If your tankless heater is exposed to extremes weather conditions, it will run a greater risk of premature failure. So, make sure your appliance is away from doors and windows, and never installed in the garage or basement.

What is the lifespan of a tankless water heater?

Tankless water heaters usually last for around 15-20 years before they need to be replaced, but they may need replacing sooner if they start to break down or lose efficiency. Some common signs your tankless water heater needs to be replaced include: Low water pressure. Water doesn't get hot.

Can you take a long hot shower with a tankless water heater?

While a tankless water heater will deliver an unlimited stream of hot water, they struggle to deliver a lot of hot water at one time. So while you might be able to take 100 showers in a row if you have the dishwasher, washing machine, and shower going at the same time you might have problems.

What size tankless water heater to replace a 50 gallon?

A 50-gallon water heater should be replaced with a tankless system with a 10 GPM flow rate just to be safe. Selecting the right flow rate ensures you won't experience cold showers or excessive energy costs. Proper sizing optimizes performance, providing hot water on demand without unnecessary waste.

Why not buy an electric tankless water heater?

Additional Installation Costs

Tankless water heaters are much more complex than traditional hot water tanks. As a result, they require professional installation. If you're switching from a hot water tank to a tankless unit, you will likely need your gas lines rerouted, as well as a larger gas supply line.

Why does my shower go cold after a few minutes tankless water heater?

One possible reason for a tankless water heater going cold after a few minutes is the occurrence of a cold water sandwich effect. This happens when the unit is turned on and the initial cold water mixes with the hot water, resulting in an inconsistent flow of hot water.

What size tankless water heater do I need for a 3 bedroom 2 bath house?

Proper sizing is important prior to select and installing a tankless, but in general the average rules for sizing the correct water heater for a household are roughly: 3.5 GPM for 1-2 fixtures simultaneously. 5 GPM for 2-3 fixtures simultaneously. 7 GPM for 3-4 fixtures simultaneously.

Why would someone use a tankless water heater instead of a conventional one?

The initial cost of a tankless water heater is greater than that of a conventional storage water heater, but tankless water heaters will typically last longer and have lower operating and energy costs, which could offset their higher purchase price.

What are the downsides of tankless water heaters?

Tankless water heaters have several drawbacks and disadvantages, including a higher initial cost, limited flow rate, specialized venting requirements, potential need for additional equipment, limited hot water supply, delayed hot water delivery, mineral buildup and maintenance, complexity of installation, dependence on ...

Is it worth converting to a tankless water heater?

Even for homes with high water usage, up to 85 gallons per day, tankless water heaters can offer up to 14% energy efficiency savings. However, while they offer energy savings, the higher upfront costs and installation expenses can result in a long payback period, ranging from 12 to 27 years.

Do tankless water heaters increase water bill?

Because tankless water heaters only consume energy when you need hot water, they're more energy efficient, saving you money on water and energy bills.

What is the upkeep on a tankless water heater?

Steps for Maintaining a Tankless Water Heater
  • Turn Off The Energy Source. ...
  • Close All Main Water Valves. ...
  • Remove Purge Port Valve Caps. ...
  • Attach Hoses To Each Valve. ...
  • Open the Port Valves. ...
  • Descale. ...
  • Flush and Drain the Unit.

Why would someone want a tankless water heater?

Tankless water heaters heat only as much water as you need. They heat the water when it's needed. This on-demand heating makes the units more energy efficient. Compared to traditional water heaters, tankless models can reduce energy use by up to 34 percent.

What is the best tankless water heater?

7 Best Tankless Water Heaters for Large Homes in 2025
  • Best Overall: Rinnai RU199iN.
  • Best Premium: Navien NPE-240A.
  • Best Gas Option: Rheem RTGH-95DVLN.
  • Best Electric: Stiebel Eltron Tempra 36.
  • Best Value: EcoSmart ECO 36.
  • Best Compact: Takagi T-H3-DV-N.
  • Best Warranty: Noritz NR981-DVC-NG.

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