The 5 Best Tankless Water Heaters of 2026
A tank water heater keeps 50 gallons hot around the clock, even while you are at work. A tankless unit heats water only when the tap opens, which can cut standby energy waste for good. The catch is sizing: flow rate, fuel type, and climate decide whether you get endless hot water or a lukewarm shower. We evaluated 20 gas, electric, and propane models against real specs like GPM, UEF efficiency ratings, and warranty terms, and five rose above the rest: our Best Overall pick for most homes, a Best Budget point-of-use option, a Best Premium condensing upgrade, an Best Electric no-vent choice, and a Best Propane pick for propane setups. Here is how they compare and how to size one for your home.
| Product | Flow Capacity | Energy Efficiency | Installation Ease | Value | |
|---|---|---|---|---|---|
 Best OverallRheem RTGH Series 8.4 GPM Tankless Water Heater | 9.2 | 9.5 | 7.5 | 8.8 | See PriceAmazon |
 | 6.0 | 9.0 | 9.5 | 9.2 | See PriceAmazon |
 Best PremiumRinnai RX130iN Condensing Tankless Water Heater | 8.5 | 9.4 | 8.2 | 7.8 | See PriceAmazon |
 Best ElectricStiebel Eltron Tempra 24 Trend Tankless Water Heater | 8.3 | 8.8 | 8.0 | 8.5 | See PriceAmazon |
 Best PropaneAPUS Propane Tankless Water Heater 95,000 BTU | 7.5 | 8.2 | 7.8 | 9.0 | See PriceAmazon |
Rheem RTGH Series 8.4 GPM Tankless Water Heater
Best for
This is the default choice for a natural gas home with two or more bathrooms. With 8.4 GPM at a 35-degree rise, it handles 3 to 4 showers running at once, which covers busy mornings in most households. If your home runs on natural gas and you want one purchase that ends the hot water queue, start here.
Why we love it
I keep coming back to the 0.93 Uniform Energy Factor, the highest efficiency figure in this roundup. Condensing technology captures heat that non-condensing units vent away, and Rheem claims up to 34 percent lower energy use than a 50-gallon tank. The 8.4 GPM output beats the Rinnai RX130iN on raw flow while costing about a hundred dollars less, and the 15-year heat exchanger warranty is the longest coverage of any gas pick here. Digital controls hold temperature within 1 degree, built-in freeze protection covers cold climates, and LeakGuard leak detection adds a layer of protection most competitors skip. Professional installation is required, which is standard for whole-house gas units.
Pros
- 8.4 GPM at 35F rise, enough for 3 to 4 simultaneous showers
- 0.93 UEF condensing efficiency, up to 34% energy savings vs tank
- 15-year heat exchanger warranty, longest of any gas pick
- LeakGuard leak detection and freeze protection built in
Cons
- Professional installation required, adds to total cost
- Indoor direct-vent installation only, no outdoor option
- At 157,000 BTU, needs adequate gas line capacity
Verdict
Yes if your home has natural gas and you want the most efficient whole-house option at a fair price. The Rinnai RX130iN is the better buy if you need outdoor installation or smart-home features. The Stiebel Eltron Tempra 24 is the move if you have no gas line at all.
ThermoMate 4.5kW Under Sink Tankless Water Heater
Best for
This is for anyone who wants instant hot water at a single sink without touching the main water heater. Garages, guest bathrooms, kitchen prep sinks, and RV wet bays are the sweet spots. If you need whole-house coverage, this is not your unit: look at the Rheem RTGH instead.
Why we love it
I like how honest this little unit is: 4.5kW of power in a box barely bigger than a paperback, delivering hot water at the tap in seconds. The self-modulating element runs at 99.8 percent efficiency, so almost every watt becomes hot water, and the cast aluminum element resists scale buildup far better than exposed coils. The touch panel adjusts temperature in 1-degree increments, and at 139.99 it costs less than most plumbers charge for a service call. Compared with the Stiebel Eltron Tempra 24, it needs only a standard 120V outlet and fits under a cabinet, which makes it a weekend DIY project rather than an electrician visit.
Pros
- 974 reviews at 4.4 stars, proven reliability
- Compact 10.95 x 7.4 x 2.52 inch footprint fits under sinks
- 99.8% efficiency with self-modulating power
- 120V power, no special electrical work
Cons
- Point-of-use only, cannot serve a whole house
- 4.5kW maxes out around one fixture at a time
- No WiFi or app control
Verdict
Yes if you want fast hot water at one sink or fixture on the cheap. If you need shower-level flow from an electric unit, step up to the Stiebel Eltron Tempra 24. If the whole house runs on gas, the Rheem RTGH is the real answer.
Rinnai RX130iN Condensing Tankless Water Heater
Best for
This is for the homeowner who wants the smartest, most flexible gas unit available and does not mind paying for it. The Versa Vent design installs indoors or outdoors, and it runs on natural gas or propane, which makes it the choice when your setup is unusual. Tech-forward buyers who want app control and quick maintenance will appreciate it most.
Why we love it
I rate this the best-engineered unit in the roundup. The condensing design rivals the Rheem RTGH on efficiency, but the RX130iN adds Versa Vent installation, so it goes indoors or outdoors, plus a Quick Flush feature that simplifies the annual maintenance most gas units need. The 5-year labor warranty is unusual: most brands cover parts only, while Rinnai backs the workmanship too. Smart Sense monitoring and an intuitive interface give you real visibility into the system, and the 15-year heat exchanger warranty matches the best in class. It costs about a hundred dollars more than the Rheem while delivering slightly less flow, so you are paying for flexibility and refinement rather than raw output.
Pros
- Indoor or outdoor installation with Versa Vent
- Quick Flush feature simplifies annual maintenance
- 5-year labor warranty on top of 15-year heat exchanger
- Smart Sense monitoring and intuitive controls
Cons
- Most expensive pick in the roundup
- Lower GPM than the Rheem RTGH at a higher price
- Professional installation required
Verdict
Yes if you want maximum installation flexibility and the best warranty package, and the premium does not bother you. For pure value in a natural gas home, the Rheem RTGH delivers more flow for less money.
Stiebel Eltron Tempra 24 Trend Tankless Water Heater
Best for
This is for homes without a gas line, or anyone who wants whole-house hot water without venting. No flue, no gas plumbing, no combustion air requirements: just electricity. If your panel can support it, installation is far simpler than any gas unit.
Why we love it
I appreciate how this unit sidesteps the biggest headaches of gas tankless: no venting, silent operation, and a compact white enclosure that mounts almost anywhere. The 24kW output delivers genuine whole-house flow for most climates, and the digital display lets you dial in the exact output temperature. It is the only pick here that a competent electrician can install without a gas fitter, which keeps total project cost down even though it needs a 150-amp minimum service. Compared with the ThermoMate, which serves one fixture, the Tempra 24 is a true whole-house replacement. Electric rates vary by region, so running costs depend on your utility, but the unit itself is superbly built.
Pros
- No venting or gas line required
- Silent operation with digital temperature display
- Compact wall-mount design saves space
- 24kW output covers whole-house use in most climates
Cons
- Requires 150A minimum electrical service, may need panel upgrade
- Electric rates can make running costs higher than gas
- Fewer reviews than the most popular picks
Verdict
Yes if your home lacks gas service or you want to avoid venting entirely. If you have natural gas, the Rheem RTGH will almost certainly cost less to run.
APUS Propane Tankless Water Heater 95,000 BTU
Best for
This is for cabins, rural homes, and anyone on propane instead of natural gas. At 4.42 GPM and 95,000 BTU, it covers a shower plus a fixture or two, which suits smaller households and vacation properties. Whole-house gas families should look at the Rheem RTGH or Rinnai RX130iN instead.
Why we love it
I like that this unit is purpose-built for propane rather than adapted to it. The oxygen-free copper heat exchanger and segmented combustion are proper engineering for LP gas, and the smart CPU holds temperature within 1 degree, which matters when inlet temperatures swing in a cabin. The LED touchscreen is genuinely useful, freeze protection is built in for unheated spaces, and at 359.99 it is the cheapest way to get real tankless performance on propane. It cannot match the Rheem RTGH on flow or efficiency, but it costs less than a third as much and needs no gas-line retrofit.
Pros
- Purpose-built for propane, 95,000 BTU and 4.42 GPM
- Temperature held within 1F by smart CPU
- LED touchscreen with built-in freeze protection
- Lowest price of any whole-house-capable pick
Cons
- 4.42 GPM limits simultaneous use to about two fixtures
- Only 2-year warranty, shortest in the roundup
- Indoor installation only
Verdict
Yes if you are on propane and want affordable tankless hot water for a smaller home. For larger households on propane, the Rinnai RX130iN runs on LP too and delivers more.
Frequently Asked Questions
What size tankless water heater do I need?
Add up the flow rates of the fixtures you run at once: a shower uses about 2 GPM, a faucet about 1. In warm climates a smaller unit suffices; in cold climates groundwater is colder, so you need more power for the same temperature rise. Most homes land on a 7 to 9 GPM gas unit like our Rheem RTGH, while single fixtures do fine with a point-of-use electric unit like the ThermoMate.
Are tankless water heaters cheaper to run than tank heaters?
They eliminate standby heat loss, which is the energy a tank wastes keeping water hot 24/7. High-efficiency condensing models like the Rheem RTGH (0.93 UEF) can cut water-heating energy use by up to 34 percent versus a 50-gallon tank. Actual savings depend on your fuel type, utility rates, and usage patterns.
Do tankless water heaters need maintenance?
Yes. Gas units need annual descaling, especially in hard-water areas, and the burner should be inspected periodically. The Rinnai RX130iN includes a Quick Flush feature that simplifies the process. Electric units like the Stiebel Eltron Tempra 24 need less maintenance but still benefit from periodic checks.
Can a tankless water heater run out of hot water?
No, not in the tank sense: it heats water continuously as it flows, so supply is endless as long as demand stays within the unit's flow capacity. If you exceed the GPM rating by running too many fixtures at once, temperature drops. Sizing correctly for simultaneous use is what prevents that.
Honorable Mentions
Rinnai RE199iN Non-Condensing Tankless Water Heater
The highest flow in the roundup at 9.8 GPM and 199,000 BTU, for 1250.00 dollars. Outscored by the [[overall|Rheem RTGH]] on efficiency since it is non-condensing, but the pick for the biggest households.
See PriceAmazonMIZUDO 199,000 BTU Tankless Water Heater
Strong specs with WiFi app control at 949.99 dollars and up to 10.3 GPM. Outscored by the [[overall|Rheem RTGH]] on efficiency rating and warranty length.
See PriceAmazonWestinghouse 5.1 GPM Indoor Tankless Water Heater
A solid mid-size gas option with WiFi control at 899.99 dollars. Only a dozen reviews so far, so it stays a mention until the track record builds.
See PriceAmazon
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