What is the Downside of a Tankless Water Heater

A tankless water heater is an excellent long term investment that provides hot water on demand. It’s an energy-efficient unit that takes less space, and has a longer lifespan.

But just like any other product, tankless water heaters have their downsides and may therefore not be suitable for every home.


Curious about these disadvantages? Read the entire article familiarize yourself with these cons. After this, you should be able to make an informed buying decision.

Disadvantages of a Tankless Water Heater

What is the Downside of a Tankless Water Heater

High Upfront Cost

Tankless water heaters come with a high price tag and may not be affordable to some individuals. For instance, the average cost of the cheapest tankless water heater is $1000. This is too high a price compared to a tank system of the same capacity, costs around $500.

High Installation Costs

Tankless water heaters are more expensive due to high installation costs. On most occasions, special wiring and/or new vent pipe has to be installed to handle the increased load.

And if living in an area with hard water, you’ll need to get a water softener to avoid ruining your tankless system. Installing the water softener adds to the overall cost.

Inconsistent Water Temperature

If you are running your dishwasher, shower and washing machine simultaneously, your tankless water heater might not be able to keep up.

Therefore, when shopping for a tankless unit, be sure to look at its flow rate. The higher the flow rate, the better.

The key issue is to get a unit that is sizeable enough to meet the hot water needs of your family.

Takes Longer to Generate Hot Water

Another drawback of tankless water heaters is that they take longer to produce and deliver hot water. Remember, these heaters don’t store hot water ready for supply instantly when you need it.

After turning on your hot water tap, it can take you about a minute to get the heated water.

Note that although tank-style systems do not produce hot water instantly, they have a supply at the ready, and thus the water reaches the outlet more quickly.

Cold Water Sandwich

A cold water sandwich is where you get an initial surge of hot water, then cold water that turns hot again in seconds.

This happens when for instance, you turn off the hot water tap and on quickly when washing dishes. The taps already have hot water from moments ago.

The delay between when the hot water starts to flow and when the heater starts working again causes a burst of cold water.

And although the cold water sandwich isn’t a big issue, it can startle you if you aren’t used to it.

No Hot Water In Case of Power Outage

Without power, you get no hot water when using a tankless water heater. And although they can be powered by gas as well, you should know that they rely on an electric control panel.

So, regardless of the model you have, you’ll have no hot water in case of a power outage.

Output Limitations

A tankless water heater can only hold up to 60 gallons of hot water. At any given time, you’ll always have enough water for doing laundry, taking baths, running the dishwasher, among other things.

But then, think about a large household, are 60 gallons enough? Not at all. These systems are best suited for smaller families due to the low hot water output.

If you have a larger household, you’ll have to get more of these units to meet the demand.

Hard to Get a Lukewarm Temperature

With a tankless water heater, it’s quite challenging to achieve a lukewarm water temperature.

Remember that these units require a minimum amount of water flow to activate. And when this happens, there’s always a gap between cold and the coolest warm water that’s possible to create by mixing hot and cold water.

Frequently Asked Questions(FAQs)

Q: Can a tankless water heater increase the electric bill?

No, tankless water heaters are energy-efficient. They are actually 23 to 34 more energy-efficient than tank-style water heaters.

Q: What maintenance is required on a tankless water heater?

You need to flush the system at least once a year, clean the air filter regularly, clean the water filter from time to time and wipe down the tank often to prevent dust and debris build-up.

Q: Do you save money with a tankless water heater?

Q: How long does it take for a tankless water heater to pay itself?

A tankless water heater pays for itself with energy bill savings. However, the payback period takes a long time: 12 to 20 years for a tankless electric heater and 22 to 27 years for a gas tankless heater.

Q: Why is the installation of a tankless water heater so expensive?

The installation of these units is so expensive (especially the natural gas/propane heaters) because they require a bigger gas supply. They need a non-traditional setup, which makes the installation more expensive.

Q: How often should you flush a tankless water heater?

It would be best if you flushed a tankless water heater once per year.

Q: Can a tankless heater fill a tub?

Yes, you can fill a large tub with a tankless water heater. You won’t even run out of hot water.

Q: Where should I install my tankless water heater?

The best place to install a tankless water heater is under the sink, the pantry, the cabinet, and under the stairs, among other places. The units are compact and unobtrusive and can fit in tiny spaces.
If you must place it outdoors, ensure that it’s safe from rain, direct sunlight and insects.

Q: Can I use my existing vent for a tankless water heater?

A tankless water heater can’t pair vent piping with other appliances. You need to install new piping altogether.

Q: How fast does a tankless water heater heat water?

On average, a tankless water heater heats about 2 to 5 gallons per minute.


Familiarizing yourself with the drawbacks of tankless water heaters will help you know what to expect if you decide to go for one.

Doing so will also help you audit yourself and figure out whether you have enough money to cater for the upfront and installation costs.

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