A tankless gas water heater can replace a 50-gallon tank when its flow capacity, fuel supply, and installation requirements fit the home. The Rheem 8.4 GPM outdoor model is best suited to homes with several simultaneous hot-water needs, while the indoor Rheem 7.0 GPM model targets homes with two or three active water points. The Rinnai offers a high listed efficiency factor and flexible installation options; GASLAND’s two models provide lower and higher flow choices.
| Product | Listed flow rate | Installation | Best suited for |
|---|---|---|---|
| GASLAND CE686NG | Up to 7.6 GPM | Indoor | Higher-flow indoor replacement |
| Rheem RTG Outdoor | 8.4 GPM at 35°F rise | Outdoor | Multiple simultaneous showers |
| Rheem RTG Indoor | 7.0 GPM at 35°F rise | Indoor | Two or three active water points |
| Rinnai RX130iN | Up to 7.1 GPM | Indoor or outdoor | Flexible installation and high listed UEF |
| GASLAND CE528NG | Up to 5.8 GPM | Indoor | Lower-flow household demand |
GASLAND Gasmart E CE686NG
Best for: Households seeking a higher-flow indoor natural gas model with a compact wall-mounted design. GASLAND lists up to 7.6 GPM and 199,000 BTU for this unit. Its on-demand design avoids storing a tank of heated water, and the product listing identifies CSA certification and multiple safety features.
The manufacturer lists a UEF of 0.8 and states that this model is more energy efficient than a 50-gallon gas tank. Treat that comparison as manufacturer-provided information; actual energy use depends on household demand, installation, and operating conditions. The suitcase-sized design may help free floor space when replacing a bulky tank.
Consideration: This is an indoor natural gas model. Confirm that the home’s gas supply and venting arrangements meet the installation requirements before choosing it. Its listed maximum flow is not a guarantee of that flow at every incoming-water temperature.
Rheem RTG 8.4 GPM Outdoor
Best for: Larger households that want an outdoor natural gas installation and may use several hot-water fixtures at once. Rheem lists 180,000 BTU per hour and 8.4 GPM at a 35°F temperature rise, with capacity described for three to four simultaneous showers. The non-condensing design eliminates the need for indoor venting, according to the product listing.
This model is a strong comparison choice for a 50-gallon tank replacement when the household’s peak demand is high. It provides continuous on-demand heating rather than relying on a fixed stored volume. Rheem lists a UEF of 0.82 and describes the unit as suitable for whole-house residential use.
Consideration: It is designed for outdoor installation, so it is not the right choice for a home that requires an indoor unit. Ask a qualified installer to assess the location and local requirements; listed flow depends on temperature rise and conditions.
Rheem RTG 7.0 GPM Indoor
Best for: Homes that need an indoor natural gas unit and commonly run two or three hot-water points at once. This Rheem model is listed at 160,000 BTU per hour and 7.0 GPM at a 35°F temperature rise. Its wall-mounted format can free floor space formerly occupied by a storage tank.
The product listing describes this non-condensing model as a whole-house heater with a direct-vent system and a UEF of 0.82. It is presented as a replacement option for aging tank water heaters. When comparing it with a 50-gallon tank, focus on peak simultaneous demand rather than tank capacity alone: the tank stores hot water, while this unit must heat incoming water as fixtures draw it.
Consideration: Indoor installation requires the specified direct-vent arrangement. Its stated capacity is tied to a 35°F rise, so colder incoming water or higher demand can affect available flow.
Rinnai RX130iN Smart Sense
Best for: Buyers who value installation flexibility and a high listed energy-efficiency factor. Rinnai lists up to 7.1 GPM, 130,000 BTU, and a UEF of 0.97. The Smart Sense gas control system supports natural gas or propane, and the product description says the unit can be installed indoors or outdoors.
The compact design is described as roughly the size of a small suitcase. Rinnai also lists an easy-to-use interface and a Quick Flush feature. The product listing says it can serve up to four fixtures at once, but household results depend on the flow rate and temperature rise required at those fixtures.
Consideration: Outdoor installation requires the RX-OVC vent cap. Wi-Fi control requires a Controlr module, which the listing says is not included. Confirm the fuel configuration and installation setup with a qualified professional.
GASLAND Gasmart E CE528NG
Best for: Households with more moderate peak hot-water demand that want an indoor natural gas tankless unit. GASLAND lists up to 5.8 GPM and 150,000 BTU for the CE528NG. The manufacturer also identifies a compact wall-mounted design, CSA certification, and multiple safety features.
Like the larger GASLAND model, this unit is described as providing hot water on demand and lists a UEF of 0.8. Its lower stated maximum flow makes it important to compare expected simultaneous use carefully. It may suit a home where fewer fixtures typically run together better than a model selected for several simultaneous showers.
Consideration: The listing does not provide a temperature-rise figure alongside the stated maximum flow. Do not assume 5.8 GPM will be available under every water-temperature condition; ask an installer to size the unit for the home’s climate and demand.
Buying Guide: Choosing A Tankless Heater For A 50-Gallon Replacement
How do you size a tankless heater?
Size a tankless water heater by estimating the maximum hot-water flow needed at the same time, then accounting for the temperature rise required. A 50-gallon tank describes stored capacity; it does not directly translate to a specific tankless GPM rating. List the fixtures likely to run together, such as showers, a dishwasher, or a washing machine, and use their flow requirements to estimate peak demand.
Temperature rise is the difference between incoming cold-water temperature and the desired hot-water temperature. Colder incoming water requires the heater to do more work, which can reduce the flow available at a given output. Compare products using flow figures at a stated temperature rise whenever possible, such as the Rheem models’ listed 35°F rise figures.
Should you choose an indoor or outdoor model?
Choose based on the home’s layout, available installation locations, and the product’s venting requirements. An indoor model can replace equipment in a utility area, but it requires an appropriate venting setup. An outdoor model avoids indoor venting, but it must be installed in a suitable outdoor location. The Rinnai listing offers both installation options, subject to its stated outdoor vent-cap requirement.
What fuel and gas-line details should you check?
Confirm whether the unit is designed for natural gas, propane, or both. The two GASLAND models and the listed Rheem models are natural gas products. The Rinnai RX130iN listing describes support for natural gas or propane through its Smart Sense gas control system. A qualified installer should verify that the home’s fuel supply and gas piping can support the selected unit’s requirements.
How should you compare efficiency claims?
Use the Uniform Energy Factor (UEF) listed for each product as one comparison point, not a promise of a particular bill reduction. Among these products, the listings state UEF values of 0.8 for both GASLAND models, 0.82 for both Rheem models, and 0.97 for the Rinnai. Actual energy use varies with hot-water demand, incoming-water temperature, settings, and installation. Compare like with like and review the complete product documentation.
What else should be reviewed before replacing a tank?
- Installation requirements: Check venting, clearances, mounting location, and whether the model is indoor or outdoor.
- Peak demand: Match the unit’s flow at the expected temperature rise to the household’s simultaneous fixture use.
- Fuel availability: Verify the appliance’s fuel type and the home’s supply capacity.
- Space and layout: A wall-mounted design can reduce floor-space use, but the location still needs to meet installation requirements.
- Professional assessment: Have a qualified installer review sizing and local code requirements before purchase and installation.
Frequently Asked Questions
Can a tankless water heater replace a 50-gallon tank?
Yes, if the tankless unit is sized for the home’s peak simultaneous hot-water demand and can be installed with the required fuel supply and venting. Tank capacity and tankless flow rate measure different things, so compare demand rather than matching gallon numbers.
Does tankless mean unlimited hot water?
A tankless heater does not rely on a fixed stored volume, so it can continue heating water while operating. However, it has a maximum heating and flow capacity. If demand exceeds that capacity, available flow or hot-water performance may be limited.
Is a higher GPM rating always better?
No. A higher rating can help with greater simultaneous demand, but the relevant flow depends on temperature rise and operating conditions. Choose a model that meets the household’s needs without treating its maximum listed GPM as guaranteed in every situation.
Which listed model is designed for outdoor installation?
The Rheem RTG 8.4 GPM model is specifically described as an outdoor unit. The Rinnai RX130iN listing supports indoor or outdoor installation, with an RX-OVC vent cap required for outdoor installation.
Can a tankless heater lower energy use?
Tankless models heat water on demand rather than maintaining a tank of stored hot water. The product listings provide UEF figures and energy-use claims, but actual savings depend on household use, fuel, installation, and other operating conditions.