Best Tankless Water Heater: The ultimate comparison

best tankless water heaterbest tankless water heater

Making the switch to a tankless water heater can be tempting though due to the many benefits that accompany them. Chances are that you don’t have much knowledge on the area as they are a non-flashy device that isn’t in the public eye much. This article has been written for you, to both provide you with information on tankless water heaters and make some suggestions on which models are the market leaders. Without a doubt, the best option you can buy is the Rinna RUC98iN, it is the premium tankless water heater of this comparison.

Rinnai RUC98iN Ultra Series Indoor Natural Gas Tankless Water Heater, Twin Pipe
  • INDOOR installation only. Fuel Type: NATURAL GAS.
  • Concentric or PVC venting option
  • Up to 0.96 Energy Factor/Up to 0.92 Uniform Energy Factor

What is a tankless water heater?

A tankless water heater is a device that instantly heats water as it flows through it. These heaters retain absolutely no water and aim to supply hot water in an immediate manner. Such heaters can use electricity or gas to provide the energy needed to heat the water.

What are the benefits of a tankless water heater?

  1. Save Money – around $108 a year according to US Department of Energy
  2. Reduce water consumption
  3. Unlimited hot water
  4. Take up less space than conventional heaters
  5. Less risk of substantial leaks
  6. Safer than a conventional tank

How do you install a tankless water heater?

If you are an expert electrician or plumber you may be able to install it yourself. Everyone else will require a professional which can be towards $1,000 or more.

Best tankless water heaters

Now we will overview the best water heaters available today. These vary in price and power although some models have many sub option as part of the range.

Rinnai RUC98iN Ultra Series

Rinnai RUC98iN Ultra Series

Rinnai’s RUC98IN is the premium tankless water heater in this article. Rinnai has gone a step further to install specific condensing technology that makes the utility more slimline, a quoted 95% Thermal efficiency. Residential water temperatures range from 98° F to 140° F.  Commerical entities can purchase an additional controller to increase this to 185° F.


  • Efficient
  • Compact
  • Accurate temperature control
  • Indefinite hot water
  • Attentive customer service
  • Huge savings
  • Minimal maintenance
  • Quiet


  • Expensive
  • Dip in water pressure
  • Rare customer issues

Rinnai RUC98iN Ultra Series Indoor Natural Gas Tankless Water Heater, Twin Pipe
  • INDOOR installation only. Fuel Type: NATURAL GAS.
  • Concentric or PVC venting option
  • Up to 0.96 Energy Factor/Up to 0.92 Uniform Energy Factor

Rheem RTEX-13

Rheem 240V Heating Chamber RTEX-13

Rheems RTEX-13 is the cheapest tankless water heater, although it admittedly isn’t as on point as the others. It does the job of saving money and overall delivers an accurate temperature, although it tends to be limited to just one shower at a time. Some users also report leaks although this isn’t too common of an event.


  • Indefinite hot water
  • Solid savings
  • Fast heating
  • Digital temperature control
  • Cheaper


  • Some temperature fluctuations on ALL HOT mode
  • One function at a time
  • Reported leaks

Rheem 240V Heating Chamber RTEX-13 Residential Tankless Water Heater
  • External adjustable digital thermostatic control with LED display (+/1 degree accuracy
  • Durable Copper immersion two heating elements, field Serviceable.Self-modulating power...
  • Simple installation – 1/2 NPT adapters included; side 1/2 inch Compression water...

Stiebel Eltron Tempra Plus 36 kW

Stiebel Eltron Trend Tempra

Stiebels Eltron Tempra Plus is a robust option in the mid-price range. It delivers on its promise of producing instantly hot water that can support multiple streams at once, although admittedly there are some reports of the water pressure and poower dips during use.


  • Indefinite water
  • Works on multiple showers/faucets at once
  • Accurate temperature setting
  • Huge savings
  • Long life span


  • Some reduced water pressure
  • Minor power dip during usage

Stiebel Eltron Tankless Water Heater – Tempra 29 Plus – Electric, On Demand Hot Water, Eco, White
  • On demand a continuous and unlimited supply of hot water
  • Sleek design saves space and no venting required
  • Requires hard-wired 240 or 208-volt electric service, with a maximum draw of 28,800 watts...

EcoSmart ECO 27 Electric Tankless Water Heater

EcoSmart ECO 27

EcoSmarts ECO 27 is certainly one of the best tankless water heaters on our list, especially when considering the price.  It performs in delivering consistent hot water across multiple showers and faucets at once, as well as providing long term monetary gains. EcoSmarts ECO 27 is reliable other than the odd report of leakages and limited life span, although it has an extended warranty of 7 years.


  • Well priced
  • Indefinite water
  • Reliable
  • Technical support
  • Easy maintenance
  • Remote thermostat
  • Works during simultaneous showers
  • Self-modulating – no power dip
  • Huge savings


  • Reports of some leaks
  • Only lasts a few years for some
  • Can struggle in cold water

EcoSmart ECO 27 Electric Tankless Water Heater, 27 KW at 240 Volts, 112.5 Amps with Patented Self Modulating Technology
  • Savings of up to 50% on water heating costs. Dimensions :17H x 17W x 3.625D inches ;Pipes...
  • Digital temperature control in 1-degree increments allows control of hot water; Activation...
  • Copper and stainless components designed for efficiency, durability and easy replacement.

Rheem RTG-64DVLN Tankless Natural 

Rheem 240V 2 Heating Chambers RTEX-1

Rheems RTG-64DVLN is a cheaper tankless heater that proficiently boosts cold water up to solid temperatures. It is compact and silent which are pleasant additions to the utility. However, take note that this is an electric tankless water heater and there is no gas option.


  • Indefinite water
  • Silent
  • Works during simultaneous showers
  • Large savings
  • Cheap
  • Heats up cold water well
  • Compact
  • Digital dial


  • Some temperature variation
  • Common internal part failures
  • Not gas
  • Power fluctuations

Rheem RTG-64DVLN Prestige Low NOx Indoor Direct Vent Condensing Tankless Natural Gas Water Heater
  • Natural Gas Tankless Water Heater
  • Direct Vent Indoor
  • 6.4 gal/min. at 35-Degree Rise

Takagi T-KJr2-IN-LP Indoor Tankless Water Heater 

EcoSmart ECO 27

A final mid-ranged tankless heater comes from Takagi. It is straightforward to use a device with an easy to comprehend manual. It is advertised as propane but the reality is that it is only natural gas.


  • Indefinite water
  • Saves money
  • Reasonably priced
  • Easy manual
  • Handle two showers at once


  • Advertised as propane but only natural
  • Not best designed

Final Word

Tankless water heaters aren’t fancy, they are straight to the point. We have provided a range of options of which there will be one that can fit your budget and needs suitably. Thanks for reading this comparison of the best tankless water heaters you can get.

Rupert Pople

Rupert is the founder of this website and a smart home tech enthusiast fascinated by the power of connected devices. Within his Business Management (BSc) degree at the University of Nottingham, he studied the technological impact of the Internet of Things.

Leave a Reply

Your email address will not be published. Required fields are marked *

Back to top button