The best tankless water heater depends on how much hot water you need at once, your available fuel and electrical supply, and whether you want whole-home or point-of-use heating. My best overall pick is the Rinnai RX199iN, a high-capacity condensing gas model for buyers seeking whole-home output; the Rheem RTEX-24 is a strong electric choice for homes with the service capacity to support it, while the Rheem RTEX-04T suits a single sink or fixture. The tradeoff is clear: larger units can serve more demand but need more substantial utilities and installation, while compact electric models are easier to target at one fixture but cannot replace a whole-home system. Portable propane units serve a different need, such as outdoor showers and camping. Read on for the full comparison, selection criteria, and advice on choosing the right size and type.
Get furniture and decor delivered free with Prime
- Fast, free delivery on millions of items
- Prime Video, Amazon Music and more included
- Member-only deals all year
Complete the kit
Key Takeaways
- Whole-home capacity and installation demands go together: the Rinnai RX199iN and Rheem RTG propane model offer a different scale of service from the electric point-of-use heaters, but require suitable gas connections, venting or outdoor placement, and professional planning.
- Electric models are not interchangeable by kilowatt rating alone: the 240V Rheem RTEX-24 targets heavier household demand, while 11–18 kW options fit more limited loads; the home’s panel capacity and local winter inlet-water temperature affect what each can deliver.
- Point-of-use units solve narrow problems: the Rheem RTEX-04T and 110V, 3000W under-sink models can serve a nearby fixture, but their output is not a substitute for showers and multiple fixtures running together.
- The roundup includes a distinct off-grid choice: the CAMPLUX 5L propane portable heater is suited to outdoor shower use, not as a direct replacement for a permanently installed residential whole-home system.
- Brand and headline capacity do not settle the choice: installation requirements, fixture demand, utility limits, and intended location separate the residential Rheem and Rinnai models from small generic electric heaters and portable propane equipment.
| tankless water heater | Voltage | Power | Flow rate | Dimensions |
|---|---|---|---|---|
| Rheem 18kW 240V Tankless Elect | 240 V | 18 kW | Up to 4.4 GPM | 14.5 × 18.25 in |
| Rheem RTEX-13 240V Residential | 240 V | 13 kW | Up to 3.17 GPM | — |
| CAMPLUX 4.5 kW Electric Tankle | 120 V | 4.5 kW | — | 7.4 × 10.9 × 2.52 in |
| 3000W Electric Tankless Water | 110 V | 3000 W | — | 4.32 × 7.86 × 1 in |
| Rheem RTEX-24 24 kW Electric T | 240 V, single-phase | 24 kW | Up to 5.9 GPM | — |
| CAMPLUX 5L Portable Tankless W | — | — | 1.32 GPM | — |
| 110V Tankless Electric Water H | 110 V | — | 0.5 GPM | 4.32 × 7.86 in |
| Rheem RTEX-04T 3.5 kW Point-of | 120 V, single-phase | 3.5 kW | Up to 0.5 GPM (listed spec also states 0.9 GPM) | — |
| 14kW Tankless Electric Water H | 240 V | 14 kW | Up to 3.38 GPM | 14.2 × 9.5 × 3.1 in |
| Rheem RTG Series 7.0 GPM Liqui | — | — | Up to 7 GPM | 13.5 × 20.75 × 9.4 in |
| NOVIEEX 18 kW Electric Tankles | 240 V | 18 kW | — | 11.14 × 15.86 × 3.18 inches (W × H × D) |
| Rinnai RX199iN Condensing Tank | — | — | Up to 11.1 GPM | 18.5 × 30.11 × 11.4 inches (W × H × D) |
| 110V 3000W Tankless Electric W | 110 V | 3000 W | — | 4.32 inches W × 7.86 inches H |
| Rheem 11 kW Multi-Fixture Tank | 240 V | 11 kW | Up to 2.68 GPM | 8.25 inches W × 12.63 inches H |
More Details on Our Top Picks
Rheem 18kW 240V Tankless Electric Water Heater, Gray
The Rheem 18kW makes more sense for buyers who want more capacity than a small point-of-use unit without stepping up to the panel demands of the RTEX-24. Its 18 kW output and listed flow rate of up to 4.4 GPM support a broader range of household use than the RTEX-13’s 3.17 GPM, though simultaneous hot-water demand can still be constrained, especially where incoming water is cold. The external LED control offers temperature adjustment within ±1°F, while self-modulating operation adjusts power to demand instead of heating continuously. This wall-mounted model needs no venting and frees floor space, but it is not a simple retrofit: the dedicated 240 V circuit may call for electrical work. I’d choose the RTEX-24 for higher stated flow only if the home can support its much larger electrical requirements.
Pros:- 18 kW output and up to 4.4 GPM offer more capacity than the Rheem RTEX-13.
- Self-modulating heating adjusts power to demand.
- External LED control supports temperature adjustment within ±1°F.
- Compact wall-mounted installation requires no venting.
Cons:- A dedicated 240 V circuit may require professional electrical work.
- The listed flow rate may not support simultaneous fixtures in colder climates.
- Less capacity than the Rheem RTEX-24, which lists up to 5.9 GPM.
Best for: Households seeking a wall-mounted 240 V electric heater for moderate hot-water demand, with more capacity than a compact single-fixture model.
Not ideal for: Homes that regularly run several high-flow fixtures at once, or homes without electrical capacity for a dedicated 240 V circuit.
- Power:18 kW
- Voltage:240 V
- Flow rate:Up to 4.4 GPM
- Maximum temperature:140°F
- Efficiency:99.8%
- Maximum pressure:150 psi
- Dimensions:14.5 × 18.25 in
- Mount type:Wall-mounted
Our verdict“Choose this Rheem for moderate household demand when you want more flow than the RTEX-13 but cannot justify the RTEX-24’s greater electrical requirements.”
Rheem RTEX-13 240V Residential Tankless Water Heater – Gray
The Rheem RTEX-13 is the more restrained whole-home-style option in this group: its 13 kW output and up to 3.17 GPM suit modest demand better than a larger heater intended to serve more fixtures. Compared with the 18 kW Rheem, it gives up flow capacity, so running a shower alongside another hot-water draw may be a poor fit. Its 99.8% efficiency and external digital control with ±1°F accuracy make temperature setting straightforward, and the included ½-NPT adapters and 1.5 GPM water-saver shower head provide useful installation components. Those inclusions do not remove the need for a dedicated 240 V circuit or proper plumbing work. I’d favor this over the 18 kW model for a smaller household with limited demand, but not for buyers expecting generous simultaneous flow.
Pros:- Up to 3.17 GPM suits modest residential demand.
- Digital control provides temperature adjustment within ±1°F.
- Listed 99.8% energy efficiency.
- Includes ½-NPT adapters and a 1.5 GPM water-saver shower head.
Cons:- Lower flow capacity than the Rheem 18 kW and RTEX-24 models.
- Requires a dedicated 240 V circuit and may need professional installation.
- Maximum flow may not support multiple fixtures at once.
Best for: Small households or homeowners with modest hot-water demand who want digital temperature control and a compact 240 V unit.
Not ideal for: Families that commonly use showers and other hot-water fixtures at the same time, since its stated flow tops out at 3.17 GPM.
- Model:RTEX-13
- Voltage:240 V
- Power:13 kW
- Flow rate:Up to 3.17 GPM
- Energy efficiency:99.8%
- Temperature control:External digital LED control, ±1°F
- Included adapters:½-NPT adapters; ½-inch compression water connections
- Included shower head:1.5 GPM water-saver
Our verdict“Pick the RTEX-13 for a smaller home with measured hot-water demand, but step up to the 18 kW Rheem if you need more flow capacity.”
CAMPLUX 4.5 kW Electric Tankless Water Heater, 120 V
The CAMPLUX 4.5 kW has a narrower job than either Rheem: it is designed to supply one sink, not a shower or a whole home. Its compact 7.4 × 10.9-inch wall-mounted body can fit near a kitchen or bathroom basin, where on-demand heating avoids relying on a distant central heater. The touch panel and LED display make local temperature adjustment more convenient than the basic 3000W 110V heater in this lineup, and its listed 50°F temperature rise at 1.0 GPM gives a useful performance reference for sink use. The tradeoff is electrical: despite its 120 V label, it needs hard wiring, a 40 A breaker, and 10 AWG wire. I’d skip it if the goal is supplying multiple fixtures; the Rheem RTEX-13 is designed for a different, higher-capacity role.
Pros:- Compact wall-mounted design fits near a point-of-use sink.
- Touch controls and an LED display make temperature settings easy to read.
- Self-modulating power input heats water on demand.
- Lists a 50°F temperature rise at 1.0 GPM.
Cons:- Designed for one sink rather than showers or multiple fixtures.
- Requires hard wiring, 10 AWG wire, and a 40 A circuit breaker.
- Lower output than the Rheem RTEX-13 and 18 kW models.
Best for: Homeowners adding on-demand hot water to a single sink who can provide the required hard-wired 40 A circuit.
Not ideal for: Buyers seeking shower, multi-fixture, or whole-home hot water, or anyone expecting a plug-in installation.
- Model:TE05N4
- Power:4.5 kW
- Voltage:120 V
- Temperature rise:50°F at 1.0 GPM
- Maximum temperature:131°F
- Minimum activation flow:0.26 GPM
- Electrical requirements:40 A circuit breaker; 10 AWG wire; hard-wired
- Dimensions:7.4 × 10.9 × 2.52 in
Our verdict“Choose the CAMPLUX for one sink when its dedicated electrical requirements are workable; choose a Rheem model for broader household use.”
3000W Electric Tankless Water Heater, 110V
This 3000W 110V heater is the most limited-use pick here: it is aimed at sinks in kitchens, bathrooms, RVs, and other small spaces, and the product data explicitly says it is not suitable for showers. At just 4.32 inches wide and 1 inch deep, it can fit where the larger CAMPLUX 4.5 kW unit may not, making it a practical candidate for a cramped point-of-use location. Its digital display switches between Fahrenheit and Celsius, and dry-operation, leak, and over-temperature protections add useful safeguards. The compact size does not make installation plug-and-play, though: it needs vertical mounting, dedicated wiring, and a recommended breaker of at least 32 A. Compared with the CAMPLUX, this model takes up less space but offers less power and a narrower use case.
Pros:- Very slim 1-inch-deep body suits tight installation spaces.
- Digital display supports Fahrenheit and Celsius.
- Includes dry-operation, leak, and over-temperature protections.
- ETL certification is listed in the product data.
Cons:- Not suitable for showers or larger hot-water demands.
- Requires vertical installation and dedicated wiring.
- Recommended circuit breaker is at least 32 A.
Best for: RV owners or homeowners needing a compact heater for a small sink where vertical wall mounting and dedicated wiring are available.
Not ideal for: Anyone needing hot water for a shower, several fixtures, or a whole home; the product is specified for small sinks only.
- Power:3000 W
- Voltage:110 V
- Maximum temperature:131°F
- Temperature rise:82°F at 0.3 GPM; 131°F at 0.5 GPM
- Efficiency:98%
- Dimensions:4.32 × 7.86 × 1 in
- Electrical requirements:At least 2.5 mm² (13 AWG) wiring; recommended breaker of at least 32 A
- Certification:ETL
Our verdict“Choose this unit for a tightly constrained sink installation, but pick the CAMPLUX 4.5 kW if the location can accommodate a larger unit and you want more output.”
Rheem RTEX-24 24 kW Electric Tankless Water Heater, 240 V
For homes that need the most listed electric flow in this group, the Rheem RTEX-24 leads with up to 5.9 GPM and 24 kW of heating power. That gives it more headroom than the 18 kW Rheem’s 4.4 GPM and makes it the stronger candidate for multiple fixtures, though actual output depends on incoming water temperature and household demand. Adjustable digital controls cover an 80°F–140°F range, and the wall-mounted, no-vent design saves space compared with a conventional tank. Its defining drawback is the electrical installation: it calls for three 40 A double-pole breakers, specified copper conductors, and a recommended 200 A household service. That makes it a poor match for homes with limited panel capacity. I’d only rank it above the smaller Rheem models when the home’s wiring and service can support its higher output.
Pros:- Up to 5.9 GPM is the highest listed flow rate among these five products.
- 24 kW output provides more capacity than the 18 kW Rheem.
- Digital temperature range spans 80°F–140°F.
- Wall-mounted design requires no venting and heats on demand.
Cons:- Requires three 40 A double-pole breakers and substantial panel capacity.
- Recommended household service is 200 A.
- Professional electrical planning and installation may be needed.
Best for: Households with higher simultaneous hot-water demand and a 200 A electrical service with room for the required breakers.
Not ideal for: Homes with limited electrical service, crowded panels, or buyers seeking a simple replacement without substantial electrical planning.
- Model:RTEX-24
- Power:24 kW
- Voltage:240 V, single-phase
- Flow rate:Up to 5.9 GPM
- Temperature range:80°F–140°F
- Efficiency:99.8%
- Electrical requirements:Three 40 A double-pole breakers; three sets of #8 AWG copper conductors with ground
- Recommended household service:200 A
Our verdict“Choose the RTEX-24 for higher electric hot-water demand only if your home can support its demanding breaker and service requirements.”
CAMPLUX 5L Portable Tankless Water Heater (AY132) – 1.32 GPM Propane Outdoor Shower for Camping & RV
I’d choose the CAMPLUX AY132 for outdoor washing where a household water line and electrical outlet aren’t available. Its propane burner, two D-size batteries, and 3.0 PSI minimum startup pressure let it work with a gravity bag or small pump, a useful advantage over the under-sink electric models in this lineup. At 1.32 GPM, it suits a basic camp shower, not several fixtures or a high-flow indoor shower. The 114°F temperature ceiling is also lower than the Rheem RTEX-04T’s adjustable 140°F maximum, though that comparison favors indoor sink use rather than portability. I’d shortlist it for camping and RV outdoor setups, but skip it if you need a whole-home heater or want to avoid carrying fuel and batteries.
Pros:- Propane and battery operation avoids dependence on mains electricity.
- Starts at 3.0 PSI, accommodating gravity-fed bags and small pumps.
- At 10 lb with a folding handle, it is practical to carry between campsites.
- Overheat and anti-flame protections add safeguards for portable use.
Cons:- The 1.32 GPM flow is suited to a modest outdoor shower, not multiple fixtures.
- Operation depends on carrying and replacing two D-size batteries.
- The 114°F temperature limit is below the maximum listed for several indoor options.
Best for: Campers, RV owners, and off-grid users who need a portable outdoor shower with a low-pressure water source.
Not ideal for: Households seeking a permanent indoor heater, multiple-fixture hot water, or a higher maximum temperature than 114°F.
- Model:AY132
- Fuel type:Propane
- Power source:2 D-size batteries
- Flow rate:1.32 GPM
- Heat output:34,000 BTU
- Maximum temperature:114°F
- Minimum water pressure:3.0 PSI
- Weight:10 lb
- Safety certification:CSA approved
Our verdict“Choose the CAMPLUX AY132 for portable, off-grid outdoor showers; choose a fixed electric or gas model for higher flow or indoor use.”
110V Tankless Electric Water Heater, 3000W, Under-Sink Instant Hot Water Heater with Digital Display
This 110V, 3000W heater is aimed at one nearby sink, where its small wall-mounted body and LCD controls matter more than whole-home capacity. The display’s Fahrenheit/Celsius selection makes temperature adjustment straightforward, while dry-boil, leakage, and IPX4 protections address common concerns around an appliance installed near water. Its stated 0.5 GPM flow is the limiting factor: it can serve a low-flow tap, but the product data specifically rules it out for showers needing 1.8 GPM or more. Compared with the Rheem RTEX-04T, it offers similar point-of-use scale and a higher stated maximum temperature, but the electrical installation requires a 32A breaker and heavy-gauge wiring. I’d pick it for a small sink only if the circuit can support it.
Pros:- Compact wall-mount format frees under-sink space.
- LCD offers digital temperature control in Fahrenheit or Celsius.
- Dry-boil, leakage, automatic shutoff, and IPX4 protections are listed.
- 98% thermal efficiency is specified for point-of-use operation.
Cons:- The 0.5 GPM rating is not suitable for typical higher-flow shower needs.
- Installation calls for a 32A breaker and wiring of at least 2.5 mm².
- Vertical-only mounting limits placement options.
Best for: Apartment residents, RV owners, or homeowners adding hot water to one compact sink with a suitable dedicated electrical circuit.
Not ideal for: Anyone seeking shower or multi-fixture flow, or buyers unable to provide the specified 32A breaker and heavy-gauge wiring.
- Voltage:110 V
- Power output:3,000 W
- Heat output:10,236 BTU
- Flow rate:0.5 GPM
- Maximum temperature:131°F
- Thermal efficiency:98%
- Dimensions:4.32 × 7.86 in
- Mounting:Wall-mounted; vertical orientation only
- Certifications and protection:ETL; IPX4, leakage protection, dry-boil protection, automatic shutoff
Our verdict“Pick this unit for a single low-flow sink when its electrical requirements fit; choose a higher-flow model for showers or several fixtures.”
Rheem RTEX-04T 3.5 kW Point-of-Use Tankless Electric Water Heater
The Rheem RTEX-04T is a compact point-of-use choice for a single sink, with digital adjustment from 80°F to 140°F and no venting requirement. At 4 lb and only 3 inches deep, it can fit where a larger multi-fixture unit would be excessive. Its role is narrower than the ORBEK 14kW heater: the ORBEK is specified for up to 3.38 GPM and multiple fixtures, while this Rheem is limited to one low-flow application. The tradeoff is electrical rather than spatial: the RTEX-04T calls for a dedicated 30A breaker, #10 AWG copper conductors, and at least a 100A household panel. I’d favor it for a sink close to the heater, but not for a shower or a home with limited electrical capacity.
Pros:- Small, 4 lb wall-mounted body fits tight point-of-use spaces.
- Digital controls provide an 80°F–140°F temperature range.
- No venting is needed for this electric model.
- Warranty data lists five years for leaks and one year for parts.
Cons:- Intended for a single low-flow fixture rather than whole-house service.
- Requires a dedicated 30A breaker and #10 AWG copper wiring.
- The specified minimum household panel service is 100A.
Best for: Homeowners adding on-demand hot water to one low-flow sink who have a compatible 120V circuit and electrical panel.
Not ideal for: Families needing shower or multi-fixture capacity, or owners whose panel cannot support a dedicated 30A circuit.
- Model:RTEX-04T
- Power:3.5 kW
- Voltage:120 V, single-phase
- Flow rate:Up to 0.5 GPM (listed spec also states 0.9 GPM)
- Temperature range:80°F–140°F
- Breaker and wiring:30A single-pole breaker; #10 AWG copper with ground
- Dimensions and weight:10.88 × 5.88 × 3 in; 4 lb
- Maximum pressure:150 PSI
- Warranty:5-year leak; 1-year parts
Our verdict“Choose the RTEX-04T for a compact, single-sink installation with adequate electrical service, not for showers or multiple taps.”
14kW Tankless Electric Water Heater – 240V, 3.38 GPM
Among the electric options here, the ORBEK 14kW has the clearest case for serving more than one fixture: its listed 3.38 GPM flow is well above the 0.5 GPM point-of-use Rheem RTEX-04T and the 110V under-sink unit. That additional capacity can make everyday overlap between taps more practical, though actual delivered flow depends on incoming water temperature and use conditions. The LED display and 86°F–140°F setting range give users direct temperature control, and its shallow 3.1-inch profile saves wall space. The tradeoff is a substantial electrical installation: it needs 240V, a 60A two-pole breaker, and 6 AWG wiring. I’d shortlist it for a modest multi-fixture electric setup, not a buyer who wants a simple plug-in replacement.
Pros:- Listed 3.38 GPM flow is more suited to multiple fixtures than the point-of-use models.
- LED display and adjustable 86°F–140°F range support precise temperature setting.
- Compact 3.1-inch depth can save wall space.
- ETL certification and multiple listed safety protections add installation safeguards.
Cons:- Requires a dedicated 240V circuit with a 60A two-pole breaker.
- The 6 AWG wiring requirement can make installation more involved.
- Its stated flow should not be read as a guarantee of that output under every inlet-water condition.
Best for: Households seeking an electric tankless unit for a modest two- or three-fixture setup and able to provide a dedicated 240V, 60A circuit.
Not ideal for: Renters, homes with limited panel capacity, or buyers who need higher capacity for several simultaneous showers.
- Power:14 kW
- Voltage:240 V
- Breaker and wire:60A two-pole breaker; 6 AWG
- Flow rate:Up to 3.38 GPM
- Temperature range:86°F–140°F
- Water connection:1/2 in NPT
- Dimensions:14.2 × 9.5 × 3.1 in
- Certification:ETL
Our verdict“Choose the ORBEK when you need more electric flow than a single-sink unit and can support its demanding circuit requirements.”
Rheem RTG Series 7.0 GPM Liquid Propane Tankless Water Heater Outdoor – 160,000 BTU High Efficiency On-Demand Continuous Hot Water (Non-Condensing)
For buyers who need gas-fired capacity rather than a sink-only electric unit, the Rheem RTG-70XLP-3 is the lineup’s large-household choice. Its listed 7 GPM flow and high BTU output put it in a different class from the CAMPLUX AY132 portable heater, which is designed for a single outdoor shower at 1.32 GPM. The Rheem is intended for permanent exterior-wall installation and includes freeze and flame-failure protection, plus a digital temperature panel. That capacity comes with installation complexity: the unit weighs 39.3 lb, requires professional mounting, and needs both liquid propane and 120V power. Its non-condensing outdoor design avoids indoor venting, but it is not a portable or plug-and-play solution. I’d choose it for a properly planned multi-shower household, not a small or temporary setup.
Pros:- Listed 7 GPM flow is suited to higher household demand than portable or point-of-use models.
- Outdoor installation avoids placing the unit indoors.
- Freeze and flame-failure protections are included.
- Warranty data lists 15 years for the heat exchanger and five years for parts.
Cons:- Professional exterior-wall installation is required.
- At 39.3 lb, handling and mounting take more planning than with compact sink heaters.
- Requires liquid propane and 120V power, limiting where it can be installed.
Best for: Larger households with liquid propane service that need sustained hot water across multiple fixtures and can arrange professional outdoor installation.
Not ideal for: Campers, renters, and smaller homes seeking a portable, low-installation heater or lacking propane and an exterior mounting location.
- Fuel type:Liquid propane
- Flow rate:Up to 7 GPM
- Heat output:180,000 BTU/hr (product title states 160,000 BTU)
- Maximum temperature:140°F
- Power and voltage:132 W; 120 V
- Dimensions:13.5 × 20.75 × 9.4 in
- Weight:39.3 lb
- Installation:Outdoor; professional exterior-wall mounting
- Warranty:15-year heat exchanger; 5-year parts
Our verdict“Pick the Rheem RTG-70XLP-3 for a permanent propane-powered home setup with substantial simultaneous demand, not for portable or small-scale use.”
NOVIEEX 18 kW Electric Tankless Water Heater, 240 V
The NOVIEEX 18 kW pairs a slim wall-mounted body with more output than small point-of-use heaters, making it a better fit for buyers who want an electric unit serving more than one nearby tap. Its adjustable 77°F–140°F range and LED display make temperature changes straightforward, while the listed maximum flow of 4.9 GPM gives it more stated capacity than the Rheem RTEX-11. That figure depends on installation conditions and incoming water temperature, so I would not treat it as a promise of simultaneous full-flow use at every fixture. The main hurdle is electrical: it draws up to 75 A and calls for dedicated wiring and qualified installation. Its one-year warranty is also shorter than the Rheem RTEX-11’s stated coverage. I would choose it for compact electric capacity, not for an easy retrofit.
Pros:- 18 kW output and a listed maximum flow of 4.9 GPM offer more stated capacity than the Rheem RTEX-11.
- Compact wall-mounted dimensions save installation space.
- Adjustable temperature and an LED display make settings easier to read and change.
- On-demand heating avoids keeping a storage tank hot.
Cons:- The 75 A maximum current requires substantial electrical capacity and dedicated wiring.
- Actual flow and delivered temperature depend on installation conditions and incoming water temperature.
- The one-year warranty is shorter than the Rheem RTEX-11’s listed warranty coverage.
Best for: Homeowners with adequate 240 V electrical service who want a compact electric unit for nearby fixtures and can arrange professional installation.
Not ideal for: Buyers with limited panel capacity, those seeking a simple DIY replacement, or households that need a long warranty.
- Power:18 kW
- Voltage:240 V
- Maximum current:75 A
- Maximum flow rate:4.9 GPM
- Temperature range:77°F–140°F
- Efficiency:99.8%
- Dimensions:11.14 × 15.86 × 3.18 inches (W × H × D)
- Water connections:3/4-inch NPT
- Warranty:1 year
Our verdict“Choose the NOVIEEX if you want a compact, higher-output electric tankless heater and have the electrical service and installation budget to support it.”
Rinnai RX199iN Condensing Tankless Water Heater
For households that need whole-home capacity, the Rinnai RX199iN is in a different class from the electric point-of-use Rheem RTEX-11: it runs on natural gas or propane and lists up to 11.1 GPM from a 199,000 BTU heat source. That gives buyers more headroom for concurrent hot-water use, while its UEF of .98 and Quick Flush feature add efficiency and a practical maintenance aid. The choice is less straightforward than its capacity suggests. Professional installation is recommended, outdoor mounting needs a separate RX-OVC vent cap, and Wi-Fi control requires a separately sold module. At 55 pounds and larger than the electric units here, it also needs a suitable mounting location and gas setup. I would favor it over the Rheem RTEX-11 for a gas-equipped home with substantial demand, but not for a quick electric point-of-use installation.
Pros:- Supports natural gas or propane.
- Up to 11.1 GPM and 199,000 BTU suit higher household hot-water demand than the point-of-use Rheem RTEX-11.
- Indoor or outdoor installation is possible with the required outdoor vent cap.
- Quick Flush feature supports maintenance, and the listed UEF is .98.
Cons:- Professional installation and suitable gas service add complexity compared with electric point-of-use models.
- Outdoor installation requires a separately specified RX-OVC vent cap.
- Wi-Fi control requires a separately sold module.
Best for: Owners of gas-equipped homes who want high hot-water capacity for multiple fixtures and can use a qualified installer.
Not ideal for: Renters, homes without natural gas or propane service, and buyers looking for a low-complexity electric point-of-use unit.
- Fuel:Natural gas or propane
- Flow rate:Up to 11.1 GPM
- Heat output:199,000 BTU
- Efficiency:UEF .98
- Installation:Indoor or outdoor; RX-OVC vent cap required for outdoor installation
- Maximum temperature:140°F
- Dimensions:18.5 × 30.11 × 11.4 inches (W × H × D)
- Weight:55 pounds
- Warranty:Limited 15 years on heat exchanger, 5 years on parts; 5 years on labor with registration within 90 days
Our verdict“Pick the Rinnai when a gas-equipped household needs high whole-home flow and can accommodate professional installation and the required venting.”
110V 3000W Tankless Electric Water Heater with Digital Display
This 110 V, 3000 W heater is for a narrow job: supplying a small point-of-use sink, including in an RV or camping setup where a compact wall-mounted unit is more useful than a household-sized heater. Its digital display and listed protections—such as dry-boil protection and automatic shutoff—add useful controls for that role. The limit is just as clear: the product description says it is not suitable for showers, and the listed temperature rise changes sharply with flow. Compared with the Rheem RTEX-11, it asks less of the electrical setup but offers far less capacity; it is not a lower-cost substitute for a multi-fixture heater. Vertical-only installation and specified wiring and switch requirements also narrow where it can be fitted. I would choose it only for a modest, nearby hot-water draw.
Pros:- Compact wall-mounted format suits tight point-of-use locations.
- Digital display provides a direct way to view settings.
- Listed protections include dry-boil protection, leakage protection, and automatic shutoff.
- On-demand operation avoids preheating a storage tank.
Cons:- The product description says it is not suitable for showers.
- Must be installed vertically, limiting placement options.
- Specified wiring and a trip switch over 32 A require electrical planning.
Best for: RV owners, campers, and households needing on-demand hot water at one small sink with a compatible vertical mounting location.
Not ideal for: Anyone needing shower water, multiple fixtures, or a home-wide replacement; the description rules out shower use and its 3000 W output is suited to point-of-use demand.
- Power:3000 W
- Voltage:110 V
- Maximum temperature:122°F
- Temperature rise:82°F at 0.3 GPM; 131°F at 0.5 GPM
- Thermal efficiency:Up to 98%
- Installation:Wall-mounted; vertical installation only
- Dimensions:4.32 inches W × 7.86 inches H
- Water connection:1/2-inch NPT
- Warranty:24 months for quality-related issues
Our verdict“Choose this unit for a small sink or mobile setup, not as a shower or whole-home tankless water heater.”
Rheem 11 kW Multi-Fixture Tankless Electric Water Heater, 240 V
The Rheem RTEX-11 is a compact electric choice for point-of-use or limited multi-fixture demand, with a stated flow of up to 2.68 GPM and digital temperature controls from 80°F to 140°F. Unlike the gas-powered Rinnai RX199iN, it needs no venting, which can simplify placement where 240 V power is available. Its modest output also makes it a more focused choice than the 18 kW NOVIEEX: this is not the unit I would select for heavy simultaneous household use. Electrical planning remains a real constraint—the specified setup includes a 50 A double-pole breaker, #8 AWG copper conductors, and recommended minimum 100 A household service. Flow also depends on inlet-water temperature. I would favor it for a nearby sink or limited demand where compact size and no venting matter more than high capacity.
Pros:- Compact wall-mounted design fits point-of-use locations.
- No venting is required, unlike the gas-powered Rinnai RX199iN.
- Digital controls offer an 80°F–140°F temperature range.
- On-demand operation heats water only when a tap is on.
Cons:- Up to 2.68 GPM limits its suitability for heavy or simultaneous hot-water use.
- Requires 240 V service, a 50 A double-pole breaker, and specified copper conductors.
- Delivered flow and temperature depend on inlet-water temperature and system sizing.
Best for: Homeowners with suitable 240 V service who need a compact heater for a nearby sink or modest, carefully sized fixture demand.
Not ideal for: Households expecting high simultaneous demand, or owners whose electrical service cannot support the specified breaker and conductors.
- Power:11 kW
- Voltage:240 V
- Flow rate:Up to 2.68 GPM
- Temperature range:80°F–140°F
- Efficiency:99.8%
- Power requirements:One 50 A double-pole breaker; #8 AWG copper conductors with ground; recommended minimum 100 A household service
- Dimensions:8.25 inches W × 12.63 inches H
- Material:Stainless steel
- Warranty:5-year leak; 1-year parts
Our verdict“Choose the Rheem RTEX-11 for compact, vent-free electric point-of-use service when its 2.68 GPM limit matches your demand.”
How We Picked
I ranked these heaters by fit for the intended job, rather than treating every unit as a whole-home solution. The main criteria were usable capacity for the stated application, fuel and electrical requirements, installation setting, controls and day-to-day usability, and the likely maintenance and setup burden. I also separated fixed residential systems from point-of-use and portable products, since comparing them as direct substitutes would give buyers a misleading picture.
The higher positions favor models with a clearer path to serving substantial household demand, provided a home can support their utilities and installation. Electric units were judged against their voltage and kilowatt ratings, while gas models were weighed by their stated output and venting or placement needs. Compact and 110V products rank lower for general-purpose use, not because they lack a place, but because their role is narrower; buyers seeking one sink or an outdoor shower may reasonably rank them first for that specific task.
Factors to Consider When Choosing Tankless Water Heater
Before choosing a model, I would match the heater to the home’s actual demand and utility setup rather than starting with a brand or a headline capacity. These checks help prevent the common mistake of buying a technically capable unit that the property cannot power, vent, or supply with enough flow.
Match Capacity to Simultaneous Hot-Water Use
List the fixtures that may run at the same time, such as a shower and kitchen tap, rather than counting every fixture in the house. Tankless output depends on both flow demand and how much the incoming water must be heated, so a unit’s maximum flow figure does not guarantee that figure at every temperature rise. Colder incoming water can reduce the flow a heater can maintain at a comfortable temperature. Oversizing can add electrical or gas installation demands without helping a household that rarely runs multiple fixtures together. Undersizing can leave showers lukewarm when another tap opens. Use local winter water temperature and fixture flow rates when comparing manufacturer capacity charts, and ask an installer to verify the calculation.
Check Electrical Service or Gas Supply Before Buying
A 240V electric heater may need one or more dedicated circuits and substantial panel capacity; the voltage label alone does not show whether an existing panel can support it. A 110V, 3000W unit draws far less power, but its modest input also limits where it makes sense. Gas models need a compatible fuel supply, correctly sized gas piping, and a plan for exhaust venting or permitted outdoor installation. Buyers often focus on the heater and discover only later that panel upgrades, wiring, gas work, or vent changes shape the project. Have a qualified professional check the service and installation site before ordering. This step may point you toward a smaller unit or a different fuel type.
Choose Whole-Home, Point-of-Use, or Portable Use
Whole-home heaters supply a plumbing system from a central location, while point-of-use models heat water close to a single fixture and can address a long wait or a small remote sink. A compact under-sink heater is not a cheaper equivalent to a large shower-capable system; it serves a narrower job. Portable propane heaters are designed around temporary outdoor use and need suitable propane handling and operating conditions. Decide whether your problem is insufficient household capacity, one slow-to-heat fixture, or the lack of a fixed hot-water source at a campsite. Buying for the wrong use case can leave you with a unit that is either overbuilt or unable to meet the demand. Check installation location, water connections, and intended indoor or outdoor use before deciding.
Weigh Condensing Design, Venting, and Maintenance
Gas models differ in how they manage exhaust heat, and a condensing design such as the Rinnai RX199iN can involve condensate drainage and venting choices that differ from a non-condensing unit. Those details can affect installation layout, materials, and ongoing checks, so compare the manual’s requirements rather than assuming one gas heater can replace another without changes. Ask whether the location has suitable drainage, access for service, and the vent route the manufacturer specifies. Electric models avoid combustion exhaust, but their wiring and scale-management needs still matter. In hard-water areas, mineral buildup can impair performance and raise maintenance demands. Confirm the manufacturer’s service schedule and local installer familiarity before purchase.
Compare Total Project Fit, Not Just the Heater
The equipment is only one part of a tankless installation: electrical work, gas-line changes, venting, condensate drainage, plumbing alterations, and permits can all affect the project. A unit that appears simple on paper may need more supporting work than a lower-capacity alternative. Ask for a site-specific installation assessment and confirm what is included, what accessories are required, and who will handle commissioning. Check warranty terms for required professional installation and routine maintenance. For a replacement, do not assume the old tank’s connections or location suit the new unit. Paying for greater capacity makes sense only when your household demand and infrastructure can use it.
Frequently Asked Questions
Can an 11–18 kW electric tankless heater run my whole house?
It depends on your incoming water temperature, the number of fixtures operating together, and the heater’s capacity at the required temperature rise. A lower-kilowatt electric model may work for a small home or limited demand, but it can struggle to supply several high-flow fixtures at once, especially in a cold climate. Check the manufacturer’s flow chart for your local winter inlet temperature rather than relying on a headline flow number. Also have an electrician confirm that your panel and circuits can support the unit. If simultaneous showers and other fixtures are routine, compare higher-capacity electric or gas options before choosing.
Is a 110V, 3000W model enough to heat water for a shower?
These compact units are generally better suited to a low-demand, nearby fixture than to a standard shower. Their available heating power limits how much water they can warm at a useful flow, and cold incoming water makes that limitation more apparent. A sink may need much less flow than a shower, so the same heater can feel adequate at one fixture and inadequate at another. Check the product’s temperature-rise and flow specifications for your conditions before buying. If you need dependable shower hot water, compare a properly sized 240V or gas model instead.
Should I choose a large electric model or a gas tankless heater for a busy home?
Start with the home’s utility capacity and installation constraints, then compare the output each option can provide at your required temperature rise. A large electric heater such as the Rheem RTEX-24 may suit a home with adequate electrical service, but its circuit and panel demands can be substantial. Gas models can serve higher household demand, yet they require suitable fuel supply, venting or outdoor placement, and professional installation. Neither fuel type is automatically the better choice for every property. Get an installer to assess both the expected simultaneous demand and the work needed to support each option.
Can I install a portable propane tankless heater indoors or use it as a permanent home system?
A portable outdoor model such as the CAMPLUX 5L is intended for temporary outdoor use, not as a substitute for a permanently installed indoor whole-home heater. Combustion equipment requires the placement, ventilation, fuel handling, and safeguards specified by its manufacturer and local codes. Using an outdoor unit indoors can create serious carbon monoxide and fire hazards. For a permanent home installation, choose equipment designed and approved for that setting and have it installed by a qualified professional. For camping, follow the portable unit’s instructions and use it only in permitted outdoor conditions.
When does a point-of-use heater make more sense than replacing the whole-home heater?
A point-of-use model can make sense when one distant sink takes too long to receive hot water or when a small fixture needs a dedicated supply. It may address that localized issue without changing the home’s central system, but it will not increase the capacity available for multiple showers or household fixtures. Compare the cost and disruption of adding a local unit with insulating the hot-water line or changing the central system, depending on the cause of the delay. Confirm that the point-of-use unit can meet that fixture’s flow and temperature needs. For recurring shortages across the house, investigate central capacity instead.
Conclusion
For a broad whole-home recommendation, I would start with the Rinnai RX199iN if the home can support its gas, venting, and condensate requirements. The best electric choice for heavier demand is the Rheem RTEX-24, but only where the panel and installation plan can handle it; the best value for a narrower fixture need is a point-of-use option such as the Rheem RTEX-04T rather than an undersized whole-home purchase. Beginners should first identify their fuel supply, panel capacity, and simultaneous fixture demand, then use a qualified installer to confirm the match before ordering. For outdoor showers and camping, choose the portable CAMPLUX 5L instead of adapting a residential unit. The right pick is the one sized for your actual use and supported by your home’s utilities—not simply the model with the largest capacity.
Halloween Picks
halloween
As an affiliate, we earn on qualifying purchases.
