Imagine never running out of hot water again, no matter how many showers, loads of laundry, or dishes you need to handle. Tankless water heaters deliver endless hot water on demand, and they do it while saving space and energy compared to traditional tank models. But with so many options on the market, choosing the right one can feel overwhelming.
This guide breaks down nine of the best tankless water heaters across different fuel types, sizes, and use cases. Whether you need a compact unit for a small apartment, a high-capacity model for a busy family, or a portable solution for your RV, you will find clear, detailed reviews to help you make an informed decision.
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Rinnai RX199iN Condensing Smart Sense Tankless Water Heater
Best forFlexible indoor or outdoor gas installa…
- Indoor or outdoor installation
- Runs on propane or natural gas
ConsiderProfessional installation recommended
Rheem 18kW 240V Tankless Electric Water Heater, Gray
Best forPrecise temperature control for homes
- Accurate digital temperature control
- Self-modulating power saves energy
ConsiderRequires 240V electrical circuit
18kW Tankless Water Heater Electric, NOVIEEX 240V 3s Instant Hot Water Heat…
Best forCompact homes with moderate hot water n…
- High 99.8% thermal efficiency
- Adjustable temperature range up to 140°F
ConsiderLimited to 18kW power
Rheem RTG Series 7.0 GPM Natural Gas Tankless Water Heater Outdoor | 160,00…
Best forLarge families with multiple bathrooms
- High 7.0 GPM flow rate
- Outdoor installation saves space
ConsiderRequires outdoor placement
Rinnai RX160iN Condensing Smart Sense Tankless Water Heater
Best forSpace-saving gas heater with flexibility
- Indoor or outdoor installation
- Propane or natural gas compatibility
ConsiderProfessional installation recommended
ORBEK RV Tankless Water Heater, Propane, 12V DC, For RV Family & Camper
Best forRV and camper enthusiasts
- Continuous hot water on demand
- High-altitude operation mode
ConsiderRequires propane supply
APUS 27kW Electric Tankless Water Heater, 240V, Up to 6.5 GPM, 3s Instant
Best forHigh-demand homes needing 6.5 GPM
- High 6.5 GPM flow rate
- 1°F temperature adjustments
ConsiderRequires 240V and high amperage
Tankless Water Heater Electric 110V, 3000W Instant Electric Water Heater, U…
Best forPoint-of-use hot water for sinks
- Compact under-sink design
- Multiple safety protections
ConsiderLow flow rate for single fixture
Rinnai RE140iP Non-Condensing Propane Tankless Water Heater
Best forReliable propane heating for homes
- Energy-saving on-demand heating
- Strong warranty coverage
ConsiderNon-condensing less efficient
Rinnai RX199iN Condensing Smart Sense – Versatile Power
The Rinnai RX199iN is a standout choice if you want a single unit that works in almost any setting. Its Versa Vent system allows installation indoors or outdoors, and it runs on either propane or natural gas, giving you flexibility that few other models offer. The compact size, about that of a small suitcase, makes it easy to fit into tight spaces without sacrificing performance.
This condensing water heater is designed with a smart interface and a Quick Flush feature that simplifies maintenance. Its super-high energy efficiency means you will use less fuel to heat the same amount of water, which can lead to noticeable savings on your utility bills. Professional installation is recommended to get the most out of this unit, and Rinnai provides a locator tool to help you find a certified installer.
- Indoor or outdoor installation
- Runs on propane or natural gas
- Quick Flush simplifies maintenance
- Professional installation recommended
- Higher upfront cost
Rheem 18kW 240V Electric – Precise Digital Control
Brand: Rheem
A dependable electric option with excellent temperature accuracy.
If you prefer an electric tankless water heater, the Rheem 18kW model offers reliable performance with a focus on precise temperature control. The external digital thermostatic control features an LED display with +/- 1 degree accuracy, so you can set your hot water to the exact temperature you want. This level of control is especially useful for households with varying preferences.
The unit uses self-modulation to adjust power based on demand, which helps conserve energy when you only need a small amount of hot water. It delivers up to 4.4 GPM, making it suitable for simultaneous use in a typical home. Installation is straightforward with bottom 3/4-inch NPT water connections, and the copper heating elements are field serviceable, meaning you can replace them without replacing the whole unit.
- Accurate digital temperature control
- Self-modulating power saves energy
- Field serviceable heating elements
- Requires 240V electrical circuit
- Flow rate limited to 4.4 GPM
NOVIEEX 18kW Electric – High Efficiency for Small Homes
Brand: NOVIEEX
An efficient, compact electric heater ideal for smaller spaces.
The NOVIEEX 18kW electric tankless water heater is engineered for small-to-medium-sized homes, condos, and apartments. It supports 2-3 simultaneous water points, so you can run a shower and a sink at the same time without a drop in temperature. With a flow rate of up to 4.9 GPM, it handles multiple fixtures with ease.
This unit maintains a constant temperature between 77°F and 140°F, adjustable via a crystal-clear LED screen. Its anti-scald feature ensures safety, especially for families with children. Operating at an impressive 99.8% thermal efficiency, it converts nearly all the electricity it uses into heat, which can significantly reduce your energy bills compared to traditional tank heaters.
- High 99.8% thermal efficiency
- Adjustable temperature range up to 140°F
- Supports 2-3 simultaneous points
- Limited to 18kW power
- May not suit very large homes
Rheem RTG Series 7.0 GPM – Outdoor Natural Gas Power
For large families or homes with multiple bathrooms, the Rheem RTG Series offers a powerful 7.0 GPM flow rate at a 35°F temperature rise, thanks to its 160,000 BTU burner. This non-condensing natural gas unit is designed for outdoor installation, freeing up indoor space and eliminating venting concerns. It delivers endless hot water on demand, so you never have to worry about running out during peak usage.
With a Uniform Energy Factor (UEF) of 0.82, this heater saves up to 34% on energy costs compared to a standard 50-gallon electric tank heater. The durable construction and advanced safety features, including CSA certification, provide peace of mind. The digital LED display makes it easy to monitor and adjust settings, ensuring you always have the right water temperature.
- High 7.0 GPM flow rate
- Outdoor installation saves space
- Saves up to 34% on energy costs
- Requires outdoor placement
- Non-condensing design less efficient than condensing
Rinnai RX160iN Condensing – Compact Efficiency
The Rinnai RX160iN shares the same versatile design as its larger sibling, offering indoor or outdoor installation and compatibility with both propane and natural gas. Its compact size makes it a great fit for spaces where a traditional tank would be impractical. Despite its small footprint, it delivers a steady supply of hot water for typical household needs.
This condensing model is highly efficient, using less fuel to heat water compared to non-condensing units. The smart interface simplifies operation, and the Quick Flush feature makes routine maintenance a breeze. Rinnai recommends professional installation to ensure optimal performance, and their network of certified installers makes it easy to find help.
- Indoor or outdoor installation
- Propane or natural gas compatibility
- Condensing efficiency saves fuel
- Professional installation recommended
- May be overkill for small apartments
ORBEK RV Tankless – On-Demand Hot Water for Travel
If you live the RV lifestyle, the ORBEK tankless water heater is a game-changer. Powered by a 60,000 BTU propane burner, it provides continuous hot water for showers, dishwashing, and more, so you never have to wait for a tank to refill. It operates on 12V DC, making it compatible with standard RV electrical systems.
The unit features an optional RV door panel (sold separately) in black or white to match your rig’s exterior. Its high-altitude mode ensures reliable operation even when you’re camping in the mountains, thanks to oxygen-free copper heat exchangers and a brushless DC fan. Installation is straightforward with standard RV connections, so you can get it up and running quickly.
- Continuous hot water on demand
- High-altitude operation mode
- Easy installation with standard RV connections
- Requires propane supply
- Door panels sold separately
APUS 27kW Electric – High Flow for Busy Homes
The APUS 27kW electric tankless water heater is built for homes with high hot water demand. It delivers up to 6.5 GPM, enough to handle 3-4 simultaneous uses like showers, laundry, and dishwashing without a noticeable drop in temperature. This makes it a strong contender for busy households.
You can adjust the temperature from 86°F to 140°F in 1°F increments using the LED digital display, and the built-in memory function recalls your preferred settings automatically. The self-modulating technology adjusts power output based on real-time flow and temperature, reducing energy waste. Its compact wall-mounted design saves space, and multiple safety features protect against overheating and electrical issues.
- High 6.5 GPM flow rate
- 1°F temperature adjustments
- Memory function recalls settings
- Requires 240V and high amperage
- May need electrical panel upgrade
xwdzswgs 110V Under Sink – Point-of-Use Convenience
For a targeted hot water solution, the xwdzswgs 110V under-sink heater is perfect for kitchens, bathrooms, or any single fixture. With 3000W of power, it raises the water temperature quickly, providing instant hot water right where you need it. Its compact, ultra-thin design fits neatly under a sink without taking up much space.
Safety is a priority with this unit, featuring water and electricity isolation, IPX4 waterproofing, leakage protection, and dry boil prevention. Installation is easy, and the LED display shows the current temperature, so you always know what you’re getting. This is an excellent choice for adding hot water to a specific area without upgrading your whole system.
- Compact under-sink design
- Multiple safety protections
- Easy installation
- Low flow rate for single fixture
- Not for whole-house use
Rinnai RE140iP Non-Condensing – Reliable Propane Option
The Rinnai RE140iP is a non-condensing propane tankless water heater designed for indoor installation. It heats water only when needed, conserving energy compared to tank models that constantly maintain a reservoir. Its compact size makes it easy to fit into tight spaces, and the improved internal layout simplifies installation and service.
This unit comes with a solid residential guarantee: 15 years on the heat exchanger, 5 years on labor, and 1 year on parts, giving you peace of mind. It’s a dependable choice for households that want the benefits of tankless without the complexity of a condensing model. Professional installation is recommended to ensure proper setup and safety.
- Energy-saving on-demand heating
- Strong warranty coverage
- Compact design for tight spaces
- Non-condensing less efficient
- Propane only, not natural gas
Buyer’s Guide: What to Consider
Choosing the right tankless water heater involves balancing several factors. This guide covers the key considerations to help you narrow down your options and pick a model that fits your home, budget, and hot water needs.
- Fuel Type: Decide between gas (natural or propane) and electric. Gas units typically have higher flow rates and lower operating costs, but require venting and gas lines. Electric models are easier to install but may need a dedicated 240V circuit and can be less efficient for whole-house use.
- Flow Rate (GPM): Consider how many fixtures you'll run simultaneously. A typical shower uses about 2.5 GPM, so a 4-5 GPM unit suits 1-2 bathrooms, while 6-7 GPM handles larger homes. Match the flow rate to your peak demand to avoid temperature drops.
- Installation Location: Some units are designed for indoor installation, others for outdoor, and some offer both options. Outdoor models save indoor space but are subject to weather. Indoor models require proper venting for gas units. Choose based on your available space and local codes.
- Energy Efficiency: Look for high UEF ratings or thermal efficiency percentages. Condensing gas models are more efficient than non-condensing, and electric units with self-modulation reduce energy waste. Higher efficiency means lower utility bills over time, offsetting higher upfront costs.
- Warranty and Support: Check the warranty length for heat exchanger, parts, and labor. Longer warranties indicate manufacturer confidence. Also consider the availability of professional installation and customer support, especially for gas units that require specialized expertise.
Conclusion
Selecting the best tankless water heater depends on your specific situation. For most homes, gas models like the Rinnai RX199iN or Rheem RTG Series offer high flow rates and efficiency, while electric options like the APUS 27kW or NOVIEEX 18kW are easier to install and great for smaller spaces. If you need hot water on the go, the ORBEK RV unit is a solid choice.
Consider your fuel type, flow rate, installation location, and budget to make the right decision. All the heaters reviewed here are reliable, but the best one for you is the one that matches your household’s demands. Take your time, compare the features, and you will enjoy endless hot water for years to come.
Erica Steven is the founder and lead writer of WorstBrands, a site dedicated to providing honest and trustworthy reviews about outdoor gear and fashion products.
With a passion for exploring the great outdoors and staying up to date on the latest fashion trends, Erica uses her expertise to provide valuable insights into the products that matter most to her readers.
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