The Best Tankless Water Heater (Reviews)

By Michael Thomas

The Best Tankless Water Heater (Reviews)

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Choosing a tankless water heater can be difficult. There are hundreds of models and brands out there and lots of industry jargon that can be hard to understand. That’s why we spent hundreds of hours reviewing the best water heaters on the market.

In past guides we’ve covered things like tankless water heater installation and cost and electric water heaters. We’ve also written about what we consider the best type of water heater available: the trusty hybrid water heater. But in this article we’ll assume you have already decided to go with a tankless water heater and want to find the best one and try to answer one question: What’s the best tankless water heater?

The best tankless water heater

We looked at every tankless water heater on the market and our favorite is the Rheem Performance 27 kw (5.6 GPM). It’s not only the best tankless electric water heater, it’s the best option overall.

What we like

  • Corrosion-resistant parts — One of the most common reasons that tankless water heaters break is because “hard water” leads to corrosion. No manufacturer warranties cover that, so it’s important to buy a water heater built with corrosion-resistant parts. And Rheem builds some of the best.
  • High GPMs — The Rheem Performance tankless water heater is very energy efficient which means that even at low inlet temperatures you’ll get a lot of GPMs for a $500 water heater.
  • Good value — While Rheem’s tankless water heater isn’t as cheap as EcoSmart’s models, they are still cheap relative to other brands like Stiebel making it one of the best value options out there.

To learn more about prices, installation and how to evaluate tankless (on-demand) water heaters, check out this article: Tankless Water Heater Cost

Rheem vs. EcoSmart

By most measures, the  Rheem Performance 27 kw and the EcoSmart 27 kw are pretty similar products. Both are generally considered the best tankless electric water heaters on the market.

But there was one thing that makes the Rheem better than the EcoSmart: corrosion resistance.

“Hard” water leads to corrosion

In many American cities, water has minerals that can build up in a hot water heater and ultimately corrode the tank or other components. (You can see how hard your water is by looking at this map).

All of Rheem’s tankless water heaters are built with corrosion resistant metal, which means that they are less likely to leak due to “hard water.” 

EcoSmart’s tankless water heaters by contrast are made of copper, which means they can corrode quickly. And while they claim to have a lifetime warranty, it’s important to read the fine print.

EcoSmart’s warranty doesn’t cover corrosion 

EcoSmart’s warranty says: “SUCH WARRANTIES DO NOT COVER: Product failure caused by liming, sediment buildup, chemical corrosion, chlorine/chloride corrosion, or freezing.”

In other words, EcoSmart’s warranty doesn’t cover the most likely way in which it will break.

EcoSmart has bad customer service

If your EcoSmart does corrode then customer service will tell you that you should have soaked the heating components in vinegar every six months (which is quite the inconvenience). 

And that’s why the internet is full of bad reviews on EcoSmart’s products like this recent Amazon review: “I wish I had never bought this product. I’ve had to replace the heater elements twice in about 3 years at cost of about $250 for the parts ($85 for 2 elements) plus labor for each incident. I have sunk about a $1,000 into this unit and more failures are to come.”

Rheem’s tankless water heaters aren’t perfect. But they receive consistently higher ratings than EcoSmart tankless water heaters. And that’s largely due to their build quality. 

Rheem vs. Stiebel

The company that claims to offer the highest quality product is Stiebel, a German-based manufacturer. 

We compared the Rheem Performance 27 kw to the Stiebel Eltron Tempra 24 Plus. 

At $620 the Stiebel tankless water heater is $115 more than the Rheem and $145 more than the EcoSmart. 

Like the Rheem, the Stiebel Eltron Tempra is built with corrosion resistant materials. So it’s a better option than the EcoSmart. 

But at a price premium of $115 we don’t think it’s worth it given that the quality is similar to the Rheem. 

Best tankless gas water heater

We don’t recommend installing gas water heaters (see why below). But if you absolutely have to do it, we think the Rheem Performance Platinum 8.4 GPM is the best natural gas tankless water heater.

Why it’s the best option

  • Water saving feature — The Rheem Performance Platinum comes with a water saving feature that can save up to 1,000 gallons per year.
  • Energy efficiency — With an Energy Star rated uniform energy factor (UEF) of 0.93, Rheem’s tankless gas water heater can save $1,100 over 12 years compared to a standard gas water heater. (It’s worth noting this is much less than the $3,000-5,000 a hybrid water heater can save).
  • High quality product — Rheem is one of the oldest water heater manufacturers around, so they’ve had a long time to work out the kinks in their products. They are known for high quality products and good customer service.

Why we don’t recommend tankless gas water heaters

  • They’re dangerous — Gas water heaters produce carbon monoxide (CO) and nitrogen dioxide (NO2). CO poisoning sends thousands of people to the hospital each year and kills hundreds. And according to health experts, children living in homes with gas appliances are 40% more likely to have asthma.
  • Gas prices are unstable and likely to rise — Natural prices can swing by as much as 100% in a given year. And most experts expect prices to rise over the next few decades. Electricity on the other hand is likely to become cheaper.
  • Bad for the environment — Natural gas releases CO2 and methane, which causes climate change. Gas appliances also produce NO2, a pollutant that make air dirtier and less healthy both outside and inside homes.

A far better option for most homeowners is a heat pump water heater, which is considered the most energy-efficient water heater available.

Learn more about water heaters

We’ve written a lot about water heaters and covered everything from tankless water heater installation to what we consider the best water heaters out there: heat pump water heaters. If you still have questions check out one of those guides or if you’re interested in exploring other ways to increase your home’s energy efficiency check out our guide to heat pumps or LED lighting.

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