A tankless water heater can only add to the luxury of a hot shower in cold weather. Whether you are rinsing off after a long day or starting the morning with a fresh, soothing wash, a hot shower is always welcome.
The main advantage of a tankless heater is that you never run out of hot water, because it heats only the water that flows through it. It is economical and eco-friendly, and over a decade a good tankless heater can save you the cost of several tank heaters. Tankless heaters come in two main types, gas (natural gas or propane) and electric, and each has its own pros and cons. Below we compare six of the best, two gas models and four electric ones, then explain how to choose. For deeper reviews see our gas, electric and portable tankless water heater pages.
| Product | Our Rating | ||
|---|---|---|---|
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Best overall
Rheem RTG Series 7.0 GPM Natural Gas Tankless Water Heater, Indoor, 160,000 BTU |
VIEW ON AMAZON | |
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Best premium
Rinnai RX199iN Condensing Smart Sense Tankless Water Heater, Indoor or Outdoor |
VIEW ON AMAZON | |
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Best electric
Stiebel Eltron Tempra Plus 29 Tankless Water Heater, 29kW Electric |
VIEW ON AMAZON | |
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Best high-capacity electric
EcoSmart ECO 36 Electric Tankless Water Heater, 36kW, 240V |
VIEW ON AMAZON | |
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Best smart model
Westinghouse WiFi Electric Tankless Water Heater, 24kW, 240V, Whole House |
VIEW ON AMAZON | |
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Best budget
EcoSmart ECO 8 Electric Tankless Water Heater, 8kW |
VIEW ON AMAZON |
Best Tankless Water Heater Reviews in 2026
Best Gas Tankless Water Heaters
1. Rheem RTG Series 7.0 GPM Natural Gas Tankless Water Heater, Indoor, 160,000 BTU
Our favorite all-round tankless heater is this natural gas Rheem. It delivers 7.0 GPM at a 35 degree rise, which is enough for two to three showers at once, and it comes from a brand with one of the widest service networks in the country. It is a non-condensing indoor model with a direct vent system.
- 7.0 GPM at 35 degree rise, 160,000 BTU
- Indoor, direct vent, natural gas
- 0.82 uniform energy factor
- Whole-house capacity
- Enough capacity for most family homes
- Strong value for a whole-house gas unit from a major brand
- Cuts energy costs compared with a 50-gallon electric tank
- Excellent owner ratings
- Parts and service are widely available
- Needs venting and a properly sized gas line
- Non-condensing, so a little less efficient than premium models
Our Verdict: Our top pick overall: strong capacity, a trusted brand and good value for an average home with natural gas.
2. Rinnai RX199iN Condensing Smart Sense Tankless Water Heater, Indoor or Outdoor
The RX199iN is Rinnai’s flagship condensing heater. It can be installed indoors or outdoors, runs on natural gas or propane through a Smart Sense gas control and delivers up to 11.1 GPM, enough for about seven fixtures at once, from a unit about the size of a small suitcase.
- Condensing, up to 11.1 GPM
- Indoor or outdoor, natural gas or propane
- Easy-to-use interface, Quick Flush feature
- Compact, wall-mounted
- Highest capacity and efficiency in our list
- Flexible, with indoor or outdoor and either fuel
- Rinnai is a top name in tankless heating
- Top rating from owners
- By far the highest price here
- Outdoor installation needs a vent cap that costs extra
Our Verdict: The best premium gas tankless heater for a large home, for those who can afford it.
Best Electric Tankless Water Heaters
3. Stiebel Eltron Tempra Plus 29 Tankless Water Heater, 29kW Electric
The Tempra Plus 29 is the electric heater to buy when you want a whole house heated without any gas or venting. Digital temperature control combines the benefit of tankless heating with a sleek, compact design that fits almost anywhere, and it needs only a standard 240V supply, although a large one.
- 29kW whole-house electric tankless
- No venting required
- Digital temperature control
- Sleek design that fits almost anywhere
- No venting or gas line makes installation flexible
- Brand with a strong reputation for reliability
- Digital control with precise temperature
- Savings on the hot-water portion of your electric bill
- Very high electrical requirements and installation cost
- The most expensive electric unit in our roundup
Our Verdict: The best electric tankless choice for large homes with a strong electrical service.
4. EcoSmart ECO 36 Electric Tankless Water Heater, 36kW, 240V
The EcoSmart ECO 36 is a big electric whole-house heater with a sleek, compact body and a digital output temperature display. EcoSmart heaters are rated 99.8 percent energy efficient and made in the United States, and this one needs four 40-amp breakers and a 150-amp service.
- 36kW, 240V electric tankless
- 99.8 percent energy efficient, manufactured in the U.S.
- Digital output temperature display
- Requires four 40-amp breakers and a 150-amp service
- One of the largest electric units available for big homes
- Made in the U.S., from a well-known electric tankless brand
- Compact, with digital display
- Very efficient at turning electricity into heat
- Very large electrical requirements
- Costs more than smaller electric units
Our Verdict: For very large households with a strong electrical service and no gas available.
5. Westinghouse WiFi Electric Tankless Water Heater, 24kW, 240V, Whole House
The Westinghouse 24kW heater offers a maximum flow rate of 5.55 GPM with a starting flow rate of only 0.79 GPM, so it supports a shower and a sink at the same time. It works with three 40-amp breakers and 8 AWG wire, and it adds WiFi control for smart-home convenience.
- 24kW, up to 5.55 GPM, starts at 0.79 GPM
- WiFi control
- Uses three 40-amp double-pole breakers, 8 AWG wire
- Bottom 3/4-inch NPT connections
- Smart WiFi control from your phone
- Low start flow means small taps also trigger heating
- Capacity for a shower and sink at once
- Very high owner rating so far
- A newer model, with fewer reviews than the established brands
- Requires 100 amps of electrical capacity
Our Verdict: A modern, smart choice for medium-sized homes if you do not mind a newer product.
6. EcoSmart ECO 8 Electric Tankless Water Heater, 8kW
The ECO 8 is a compact, 8kW electric heater meant for a point-of-use job such as a single sink, a small bathroom or a cabin. It is small enough to fit inside a cabinet or closet, easy to use and cheap to buy.
- 8kW electric tankless
- Compact, about 12 x 8 x 4 inches
- Easy to use
- Suited to a single fixture
- Cheapest entry into electric tankless heating
- Tiny and easy to place near the fixture
- Simple to use
- Good owner ratings
- Only enough for a single sink or a very small shower
- Not suitable as a whole-house heater
Our Verdict: A neat point-of-use heater for a single sink or small bathroom.
Features to Look For in a Tankless Water Heater
- Heating power and flow rate. Hot water output is measured in GPM at a given temperature rise. A typical unit can deliver 1.2 GPM with 31,000 BTU, rising to about 5.7 GPM with 190,000 BTU. Add up the fixtures you use at the same time.
- Minimum flow rate. The lowest flow that will trigger heating. A low minimum is better for small taps.
- Energy factor and efficiency. Gas units typically range from about 78 to 87 percent, while condensing models can reach about 90 to 96 percent, and electric units are close to 99 percent efficient at turning electricity into heat.
- Fuel and location. Check for natural gas, propane or sufficient electrical capacity, and whether you need indoor or outdoor installation.
- Warranty. Good heaters carry warranties on the heat exchanger and parts, and the best ones have long terms.
Gas vs. Electric
Gas units use natural gas or propane to heat the water, while electric units use heating elements. Gas heaters generally deliver more hot water and cost less to run where gas is cheap, but they need venting and a gas line. Electric heaters are simpler to install and need no venting, but they draw a lot of power and need a strong electrical service. We explain the trade-offs in our guide to gas vs electric tankless water heaters, and our article on how tankless water heaters work covers the technology.
Conclusion
Whether it is electric or gas, a tankless water heater is the ideal answer if you are tired of worrying about a limited supply of hot water. Always check the specifications, particularly the heating capacity, build, minimum flow rate and efficiency, and read reviews of the model you are planning to buy before you commit. Most good units also come with a warranty, so choose carefully and enjoy endless hot showers.
It was a treat reading detailed reviews about the tankless heaters. Thanks.
Thanks, that’s why we are here…
Our water heater purchased nearly three years ago has been working very satisfactorily until on 20 December it started to give problems. The water was hot for about 30 seconds then went cold.
Our main problem was trying to contact Rinnai. All their phone numbers were not answering including the emergency no. for faults. They appear to have shut down all services till early January.
This is appalling service. They should at least have a hotline for answering emergency calls.
I’m sorry to hear about such a poor customer experience with Rinnai. I would think they are more professional then this.