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The Best Tankless Water Heaters

Why buy tankless water heaters?

We've evaluated tankless water heaters since 2015, spending over 50 hours researching the best manufacturers in the industry. As we created this guide, we looked at representative models from each of the 10 best brands we found. Of these models, we chose to highlight ones that are best for various uses such as whole-home, single-sink and single-bathroom water heating.

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Best for most homes

EcoSmart ECO 27

A great all round tankless water heater for most homes

Lifetime  on all parts with installation
High maintenance with mineral-rich water

The EcoSmart ECO 27 is an energy efficient tankless water heater that works well in average homes that don’t have huge demands for hot water. It can heat up to 6.5 gpm, which is enough water to supply four showers and a sink at the same time. It doesn’t produce nearly as much hot water in cooler climates, but it's still powerful enough to heat up to 3 gpm. That is enough water for two simultaneous showers and much more than smaller tankless water heaters can supply. 

The EcoSmart ECO 27 has a digital display that lets you set the exact water temperature between 80 and 140 degrees Fahrenheit. This water heater is self-modulating, which means it draws energy based on how much water you’re using and the temperature you set. 

EcoSmart includes a lifetime warranty on the water heater’s electronics, exchanger and elements, which is exceptional. However, a professional must install it to qualify for warranty coverage, and the warranty only covers the cost of the heater, not labor or incidental damages. Minerals in your water can be harsh on the copper elements, so you should soak them in vinegar about every six months to minimize corrosion.

Best budget model for under sinks

Chronomite SR-20L/240 HTR

A great tankless water heater that is low cost and ideal for under the sink

Economically priced
Heats water fast
Low power
Not suitable for cold climates

The Chronomite SR-20L/240 HTR has a flow rate of 0.5 gpm, which makes it ideal for heating the water in a single sink. It is particularly helpful if you have a sink that's far from your main water heater, as it can keep you from wasting water while you wait for it to heat up. This water heater is three times faster than average, turning out warm water within a couple seconds of turning on the faucet. 

This unit costs less than $200, which makes it an affordable way to increase your home’s hot water production without replacing your main water heater. It uses a microprocessor to regulate electricity consumption and water output temperature. As such, it can provide a steady supply of on-demand water at your preset temperature. It also does a good job raising water temperature at lower flow rates, but it can't heat water for an entire bathroom or home, especially in colder climates.

Best for most bathrooms

Rheem RTEX 13

A tankless water heater that heats water rapidly for a low price

Rapid water heating
Low power
Poor for cold climates

The Rheem RTEX 13 tankless water heater has a flow rate of 4.8 gmp, which is enough powerful to supply multiple bathrooms – up to three faucets, showers or bathtubs with hot water in warmer climates. In colder climates, however, it is less effective and may only heat a single bathroom sink and shower running together. Its compact design means you can install it under your sink or inside the bathroom vanity to keep it out of view. 

The RTEX 13 is Energy Star certified, which means it’s more efficient than standard tankless water heaters. This is because it modulates power consumption while providing a continuous hot water supply. 

Rheem includes a 10-year heat exchanger warranty, though the unit must be installed by a licensed technician to qualify for it. All other parts carry a one-year warranty.

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What to look for in a tankless water heater

Electric water heater Vs. Gas water heater

Tankless water heaters use one of three power sources: electricity, natural gas or propane. In some cases, the type you buy is dictated by the power source available in your home, so you won't have a say in the matter. Still, it's good to know what your options are if you have more than one power source.

You can expect electric models to have lower operating costs but be more expensive to buy. In contrast, natural gas and propane models cost less to buy and have slightly higher operating costs. Gas models also work when your power goes out.

Size and flow rate

The tankless water heater’s size generally impacts its hot water delivery rate. For example, if you need hot water for your entire home, you need a larger unit to keep up with the demands of people using multiple faucets. Smaller models, with a flow rate of around 0.5 gallons per minute (gpm), may only work for a single bathroom or faucet, though they can also serve to supplement a traditional water heater or add hot water to a garage sink outside your home.

Tankless water heaters can only provide a fixed amount of heating based on the temperature of the water flowing through them. As such, if you live in a colder climate, you need a larger model with a higher flow rate to produce the same amount of hot water a smaller one can in a temperate climate.

Energy efficiency

On the whole, tankless water heaters use less energy than conventional water heaters, though some models are more efficient than others. To maximize energy efficiency, look for one that is Energy Star qualified. However, keep in mind that the most efficient water heaters, like the Rinnai RUC98iN, usually have the highest prices. The Rinnai is not only efficient, it runs off both natural gas and propane, and has multiple venting options.

A professional should install your tankless water heater 

Although it's tempting to install your new tankless water heater by yourself, most homeowners simply don't have the right skills and experience. Professionals can install water heaters correctly and safely while taking less time overall. They also often have water heater suggestions for your home. Furthermore, some brands only sell through installers.

To find the best plumber in your area, take some time to look at their online customer reviews on Yelp, HomeAdvisor, Angie's List and similar websites. If they don't clearly outline their pricing and estimated completion time and provide a written quote, don't use them, even if they are the lowest bid.

How much does a tankless water heater cost? 

At the time of this writing, the tankless water heaters we reviewed cost anywhere from $130 to $1,300 – the least expensive model is the Chronomite SR-20L/240, and the most expensive model is the Rinnai RUC98iN. Our favorite tankless water heater, the EcoSmart ECO 27, falls right in the middle at $449. The average price for the tankless water heaters we compared is $478.

Keep in mind that you have to pay for installation on top of the price of the water heater itself. If you’re proficient in plumbing and electrical work, you may be able to install your water heater yourself. If not, it's important to find a professional to do it for you. The cost of installation varies widely depending on where you live.

Traditional water heaters 

Most homeowners choose traditional gas or electric storage-tank water heaters, which cost less than tankless water heaters. However, these units are also bulky, making them more difficult to transport and install. They're also not nearly as efficient as tankless water heaters.

Contributing Reviewer: Noel Case