Tankless water heaters provide hot water on demand without the standby losses of a storage tank. The right model can improve efficiency, save space, and support everything from a single bathroom to a busy household.
This roundup compares 10 gas and electric options across different flow rates, power levels, installation types, and smart features. Use the buying guide below to narrow the list based on your home’s fuel source, climate, electrical capacity, and hot-water demand.
Best 10 Tankless Water Heaters Picks for 2026
Best Outdoor Gas Pick
Rheem RTG 8.4 GPM Outdoor Tankless Water Heater
- 8.4 GPM and 180,000 BTU/hr output
- Outdoor installation avoids indoor venting
- 15-year heat-exchanger warranty
Best For: Large families and multi-bathroom homes
Best Smart Electric Option
Westinghouse 14kW WiFi Tankless Water Heater
- WiFi and voice-control compatibility
- 98% thermal efficiency
- Compact 240V wall-mounted design
Best For: Apartments and smaller homes with suitable electrical service
Best Indoor Gas Value
Rheem RTG 7.0 GPM Indoor Tankless Water Heater
- 7.0 GPM and 160,000 BTU/hr output
- Direct-vent indoor installation
- LeakGuard leak detection and prevention
Best For: Homes replacing an aging tank heater
Best High-Capacity Condensing Model
Rinnai RX199iN 11.1 GPM Tankless Water Heater
- Up to 11.1 GPM and 199,000 BTU output
- Supports natural gas or propane
- .98 UEF condensing design
Best For: Large households needing high simultaneous flow
Best High-Capacity Electric Pick
Rheem RTEX-24 24kW Tankless Water Heater
- Up to 5.9 GPM for multiple fixtures
- Compact design requires no venting
- Needs substantial electrical service
Best For: Homes with adequate electrical capacity and higher hot-water demand
Best Smart Gas Model
Rinnai RXP199iN Condensing Tankless Water Heater
- Up to 11.1 GPM for high demand
- Built-in pump with Smart-Circ recirculation
- Supports natural gas or propane
Best For: Large households wanting high flow and reduced hot-water wait times
Best Value Electric Option
Rheem RTEX-18 18kW Tankless Water Heater
- Up to 4.4 GPM flow rate
- Self-modulates to match demand
- External digital LED temperature control
Best For: Moderate household demand and straightforward electric replacement projects
Best Overall Gas Pick
High-Capacity Smart Gas Tankless Heater
- Up to 9 GPM for multiple fixtures
- Runs on natural gas or propane
- Indoor or outdoor installation flexibility
Best For: Larger households needing high-flow gas hot water
Best Compact Electric Value
14kW Electric On-Demand Heater
- Up to 3.38 GPM for two to three uses
- Compact wall-mounted design
- Digital control with ±1°F stability
Best For: Smaller homes with sufficient 240V electrical capacity
Best Established Electric Option
Rheem 11kW Multi-Fixture Heater
- Up to 2.68 GPM for moderate demand
- One-degree digital temperature control
- No venting required
Best For: Homes wanting compact electric hot water without gas venting
Best Outdoor Gas Pick – Rheem RTG 8.4 GPM Outdoor Tankless Water Heater
If you need high-capacity tankless water heaters for a whole-house setup, this outdoor Rheem model delivers up to 8.4 GPM and 180,000 BTU/hr. Its outdoor installation avoids indoor venting, while the non-condensing design and 0.82 UEF are aimed at efficient on-demand heating.
Best For: Large families and multi-bathroom homes needing natural-gas hot water for up to three or four simultaneous showers.
Pros:
- 8.4 GPM flow rate and 180,000 BTU/hr output support multiple simultaneous showers.
- Outdoor installation eliminates the need for indoor venting.
- Digital controls offer temperature adjustments within ±1°F.
- Includes freeze, flame-failure, overheat, and other safety protections.
Cons:
- Requires professional installation and a natural-gas connection.
- Outdoor placement may not suit homes without an appropriate installation location.
- Non-condensing operation requires the installation approach specified by the manufacturer.
With a strong flow rate, wall-mounted form, and a 15-year heat-exchanger warranty, this Rheem is a practical high-capacity choice. Confirm gas supply, mounting, and outdoor installation requirements before buying.
Best Smart Electric Option – Westinghouse 14kW WiFi Tankless Water Heater
Among electric tankless water heaters, this Westinghouse model stands out for its compact wall-mounted design, WiFi connectivity, and 14kW output. It heats water in about three seconds and can reach 3.4 GPM under the stated test conditions, making it suited to smaller hot-water demands.
Best For: Apartments, cabins, and smaller homes that want app or voice control and can support the required 240V electrical installation.
Pros:
- WiFi, Alexa, and Google Home compatibility enable remote temperature control.
- Compact design uses no floor space and supports wall mounting.
- 98% thermal efficiency with hot water in approximately three seconds.
- ETL certification and four-layer protection cover leakage, overheating, dry firing, and over-voltage.
Cons:
- Requires a dedicated 60A double-pole breaker and 6 AWG wire at 240V.
- The stated 3.4 GPM output is based on specific inlet and outlet temperatures.
- Its electric capacity may be less suitable for several high-flow fixtures running together.
This is a convenient choice when smart-home controls and compact installation matter more than maximum whole-house flow. Have an electrician verify the circuit requirements before installation.
Best Indoor Gas Value – Rheem RTG 7.0 GPM Indoor Tankless Water Heater
This indoor Rheem is one of the more capable tankless water heaters for homes that need natural-gas performance without a storage tank. It provides 7.0 GPM and 160,000 BTU/hr, with direct venting, a wall-mounted footprint, and a 0.82 UEF rating.
Best For: Households replacing an aging tank heater and running two or three water points simultaneously.
Pros:
- 7.0 GPM flow and 160,000 BTU/hr output support two or three simultaneous showers.
- Indoor direct-vent installation works well for homes without an outdoor mounting location.
- LeakGuard leak detection and prevention helps address internal leaks.
- Digital controls provide precise ±1°F temperature adjustments.
Cons:
- Requires professional installation and a compatible direct-vent setup.
- Uses natural gas, so it is not a fit for homes without gas service.
- Its indoor installation requires attention to venting and available wall space.
With a moderate 7.0 GPM capacity and useful leak-protection features, this Rheem offers a balanced indoor whole-house configuration. Check gas-line, venting, and installation compatibility before replacing a tank unit.
Best High-Capacity Condensing Model – Rinnai RX199iN 11.1 GPM Tankless Water Heater
For shoppers comparing high-capacity tankless water heaters, the Rinnai RX199iN offers up to 11.1 GPM and 199,000 BTU output. Its condensing design reaches a stated UEF of .98, while Smart Sense supports natural gas or propane and Versa Vent allows indoor or outdoor installation with the required accessories.
Best For: Large households that need substantial simultaneous flow and flexibility between natural-gas or propane installation.
Pros:
- Up to 11.1 GPM can support as many as seven fixtures at once, according to the supplied notes.
- Smart Sense supports both natural gas and propane.
- Versa Vent enables indoor or outdoor installation options.
- Condensing operation provides a high .98 UEF rating and includes a Quick Flush feature.
Cons:
- Professional installation is recommended.
- Outdoor installation requires the RX-OVC vent cap.
- WiFi control requires the separately sold Controlr module.
This Rinnai is a strong fit when maximum flow, fuel flexibility, and high efficiency are priorities. Confirm local venting, fuel, accessory, and professional-installation requirements before choosing it.
Best High-Capacity Electric Pick – Rheem RTEX-24 24kW Tankless Water Heater
The Rheem RTEX-24 is a whole-home option for shoppers comparing tankless water heaters that can support multiple fixtures. Its 24kW output delivers up to 5.9 GPM, while digital controls adjust temperature in one-degree increments. Verify your home’s electrical capacity before installation.
Best For: Homes needing higher-capacity electric, on-demand hot water and sufficient electrical service for a 24kW unit.
Pros:
- Provides up to 5.9 GPM for multiple fixtures.
- Compact, wall-mounted design saves floor space and requires no venting.
- Digital thermostatic controls adjust from 80°F to 140°F in one-degree increments.
- Tankless operation heats water only when a tap is turned on.
Cons:
- Requires three 40-amp double-pole breakers and three sets of #8 AWG copper conductors.
- A recommended minimum 200-amp household service panel may limit compatibility.
- Professional installation is important because of the substantial electrical requirements.
The RTEX-24 is a strong electric choice when flow capacity and space savings matter, but its demanding wiring requirements should be confirmed before purchase.
Best Smart Gas Model – Rinnai RXP199iN Condensing Tankless Water Heater
The Rinnai RXP199iN is a high-output choice for shoppers comparing tankless water heaters for busy households. It supplies up to 11.1 GPM, supports natural gas or propane, and includes an internal pump with Smart-Circ recirculation to help reduce hot-water wait times.
Best For: Larger households that need high flow, built-in recirculation, and flexible indoor or outdoor installation.
Pros:
- Delivers up to 11.1 GPM, rated for up to seven fixtures at once.
- Works with natural gas or propane through its Smart Sense gas control system.
- Built-in pump and Smart-Circ technology learn usage patterns for recirculation scheduling.
- Offers indoor or outdoor installation with the Versa Vent system.
Cons:
- Professional installation is recommended.
- Wi-Fi control requires the separately available Control-R module.
- Outdoor installation requires the RX-OVC vent cap.
With its high capacity and integrated recirculation, the RXP199iN is suited to demanding homes, though installation accessories and professional setup add planning considerations.
Best Value Electric Option – Rheem RTEX-18 18kW Tankless Water Heater
The Rheem RTEX-18 is a practical option for shoppers comparing tankless water heaters with straightforward electric installation features. Its 18kW system provides up to 4.4 GPM, uses self-modulation to adjust power to demand, and includes an external digital temperature control.
Best For: Smaller households or replacement installations that need a compact electric unit with simple temperature control.
Pros:
- Provides up to 4.4 GPM for household hot-water use.
- Self-modulation adjusts power to meet hot-water demand.
- External LED control offers temperature adjustment with plus-or-minus one-degree accuracy.
- Copper immersion heating elements are field serviceable.
Cons:
- Its 4.4 GPM flow rate is lower than the larger electric and gas models in this roundup.
- Requires 240V AC power.
- Electric capacity should be verified before installation.
The RTEX-18 balances useful flow and uncomplicated controls in a smaller electric format, making it worth considering when household demand is moderate and 240V power is available.
Best Overall Gas Pick – High-Capacity Smart Gas Tankless Heater
For households that need substantial hot-water capacity, the Rinnai RX160iN is a versatile tankless water heater that supports either natural gas or propane. Its condensing design delivers up to 9 GPM, while indoor or outdoor installation options and a compact wall-mounted form provide added flexibility.
Best For: Larger households seeking high-flow gas-powered hot water and flexible installation.
Pros:
- Up to 9 GPM can support as many as six fixtures at once.
- Supports natural gas or propane with Smart Sense gas controls.
- Indoor or outdoor installation is possible with the required outdoor vent cap.
- Highly efficient condensing design with a stated UEF of .97.
Cons:
- Professional installation is recommended.
- Outdoor installation requires the RX-OVC vent cap.
- Wi-Fi control requires the separately sold Controlr module.
The RX160iN is a strong choice when flow rate and fuel flexibility matter most. Before buying, confirm gas, venting, regional groundwater-temperature, and installation requirements with a qualified technician.
Best Compact Electric Value – 14kW Electric On-Demand Heater
The ORBEK 14kW is a compact electric tankless water heater designed for on-demand hot water at up to 3.38 GPM. Its digital controls, listed ±1°F temperature stability, and built-in protection features make it a practical option for homes with adequate electrical capacity.
Best For: Smaller homes or targeted bathroom-and-kitchen applications with a suitable 240V electrical system.
Pros:
- Provides up to 3.38 GPM for two to three points of use.
- Compact 14.2-by-9.5-by-3.1-inch wall-mounted design saves space.
- Digital controls allow temperature settings from 86°F to 140°F.
- Includes leakage, over-temperature, dry-heating, and lightning protection.
Cons:
- Requires a 240V/60A two-pole breaker and 6 AWG wiring.
- The household electrical panel should have at least 150A total capacity.
- Its 3.38 GPM output may not suit high-demand whole-home use.
With instant heating and a space-saving design, this ORBEK model can fit tight installation areas. Verify the panel, breaker, wiring, and water connections before purchase, since its electrical requirements are substantial.
Best Established Electric Option – Rheem 11kW Multi-Fixture Heater
The Rheem RTEX-11 is a compact electric tankless water heater for moderate multi-fixture demand. It provides up to 2.68 GPM, uses digital one-degree temperature controls, and requires no venting, making it an appealing alternative to gas models when the home meets its electrical specifications.
Best For: Homes needing modest multi-fixture electric hot water without gas venting.
Pros:
- Supplies up to 2.68 GPM for multiple fixtures.
- Adjusts temperature from 80°F to 140°F in one-degree increments.
- Compact design is substantially smaller than a traditional tank heater.
- No venting is required for operation.
Cons:
- Requires 240V single-phase power, a 50A double-pole breaker, and #8 AWG copper conductors.
- A minimum 100A household service panel is recommended.
- The 2.68 GPM flow rate is lower than the gas model in this roundup.
The RTEX-11 is a sensible space-saving choice for moderate demand, especially where gas venting is impractical. Confirm electrical service and sizing before installation to ensure it matches the household’s hot-water needs.
How We Picked These Tankless Water Heaters
We selected models that represent the main choices shoppers face: natural gas versus electric operation, indoor versus outdoor installation, condensing designs, multiple flow-rate classes, and connected features such as Wi-Fi monitoring. We also considered rated output, household suitability, installation flexibility, and whether each unit is better suited to a point-of-use application or whole-home service.
Specifications such as maximum flow rate and heating capacity are useful starting points, but real-world performance depends on incoming water temperature, desired temperature rise, plumbing layout, and simultaneous demand. Always confirm compatibility with the manufacturer’s sizing tools and a qualified installer.
Quick Comparison
| Best For | Recommended Type | What to Look For |
|---|---|---|
| Large households | High-output natural gas | Approximately 7–8.4 GPM, suitable venting, strong gas supply |
| Efficient whole-home service | Condensing gas | High BTU capacity, condensate drainage, indoor installation requirements |
| Smaller homes or apartments | Electric | Enough amperage, appropriate breaker space, realistic flow expectations |
| Single bathroom or remote fixture | Lower-output electric | Modest flow rate and shorter pipe runs |
| Smart-home monitoring | Wi-Fi-enabled model | App support, alerts, usage tracking, and reliable network access |
Key Buying Factors for Tankless Water Heaters
Fuel Source and Installation
Natural-gas units generally deliver higher flow rates for whole-home use, but they require gas capacity, approved venting, and often condensate management. Electric models avoid combustion and venting, making them attractive for additions, apartments, and homes without gas service. However, high-output electric Tankless Water Heaters can require substantial amperage, multiple breakers, and an upgraded electrical panel.
Flow Rate and Temperature Rise
Flow rate is measured in gallons per minute, but the maximum rating is not available under every condition. Cold incoming water requires more heating power, especially in winter. Estimate the fixtures likely to run at once—such as showers, sinks, and a washing machine—and compare their combined flow with the unit’s capacity at your local temperature rise.
Efficiency, Controls, and Maintenance
Condensing gas models can recover more heat from exhaust than non-condensing designs, while modulation helps match output to demand. Temperature controls and Wi-Fi features add convenience, but they should not outweigh correct sizing. Tankless systems also need periodic filter cleaning and, in hard-water areas, descaling according to the manufacturer’s schedule.
Installation and Warranty
Installation is a major part of total cost. Check venting, gas-line size, electrical requirements, water connections, freeze protection, service clearances, and local code rules before buying. Review warranty terms carefully, since coverage may depend on professional installation, water quality, and documented maintenance.
Who Should Buy Which Tankless Water Heaters?
Choose a high-capacity natural-gas or condensing model if you need simultaneous showers and appliances or live in a cold climate. Choose a higher-powered electric unit when you have sufficient electrical service and want a vent-free whole-home solution. A lower-output electric model is more appropriate for one bathroom, a guest suite, or a point-of-use installation. If remote monitoring matters, select a compatible smart model—but verify that its app and connectivity features are supported in your area.