Best Tankless Water Heaters for Different Home Hot Water Needs
The best tankless water heater depends on fuel, household demand, and installation requirements. For whole-house natural gas use, consider the Rheem RTGH or Rinnai RE199iN; the MIZUDO offers high stated flow and precise temperature control. The NOVIEEX is a high-output electric option, while the Westinghouse is better suited to buyers seeking a smaller electric unit with Wi-Fi features. Product details supplied do not include ratings, so these picks compare listed specifications rather than verified customer scores.
| Product | Fuel | Best For |
|---|---|---|
| Rheem RTGH Series | Natural gas | Indoor whole-house use and efficiency features |
| Rinnai RE199iN | Natural gas | High flow and diagnostic display |
| MIZUDO | Natural gas | Temperature precision and low-flow activation |
| NOVIEEX 27kW | Electric | High-demand electric installations |
| Westinghouse 14kW | Electric | Smart controls and compact installation |
Rheem RTGH Series Condensing Heater
The Rheem RTGH is best for households that want an indoor natural gas unit with stated support for several simultaneous showers. Its listed output is 8.4 GPM at a 35°F rise, powered by 157,000 BTU per hour. Rheem also lists condensing technology, a 0.93 Uniform Energy Factor, direct venting, and ultra-low NOx compliance.
Choose this model if efficiency specifications and indoor whole-house use are priorities. The supplied product information says it may use up to 34% less energy than a standard 50-gallon electric tank. Its output depends on the stated temperature rise, so compare that figure with your incoming water temperature and household demand before choosing.
Rinnai RE199iN Natural Gas Heater
The Rinnai RE199iN is best for buyers seeking a high-output indoor gas heater with service information displayed on the unit. It is listed at up to 9.8 GPM and 199,000 BTU, with capacity for multiple fixtures. Its LED display provides diagnostic codes and service reminders, and its wall-mounted design saves floor space.
Choose the Rinnai when listed flow capacity and maintenance prompts matter. The product details specify a limited warranty of 15 years on the heat exchanger, five years on parts, and one year on labor. It is non-condensing, and built-in recirculation is not listed for this model; the product description points buyers seeking that feature to a different model.
MIZUDO Natural Gas Tankless Heater
The MIZUDO is best for households that value adjustable temperature settings and low-flow activation. Its listed maximum is 10.3 GPM at 199,000 BTU, and the manufacturer describes it as suitable for simultaneous demand across two to three bathrooms, kitchen fixtures, and laundry appliances. Temperature control is listed as ±1°F, with a range up to 149°F.
Its stated 0.53 GPM activation point may suit fixtures with lower hot-water flow. Choose it if temperature precision and a high listed maximum flow are important. Maximum flow does not guarantee that every home will receive that rate: incoming water temperature and simultaneous demand affect usable output.
NOVIEEX 27kW Electric Tankless Heater
The NOVIEEX is best for buyers who need a high-output electric model and have an electrical system that can support its requirements. The listing gives a maximum flow of 7.4 GPM and describes use across three to four points. It has 3/4-inch NPT water connections and a compact wall-mounted enclosure.
Its electrical demands are a major selection factor: the supplied specifications call for 240V, 112.5A maximum current, three 40A double-pole breakers, and three sets of 8 AWG wires with ground. Consult a qualified electrician and verify capacity before purchase. Avoid choosing it based on flow alone if the home’s electrical service cannot meet those requirements.
Westinghouse 14kW Smart Electric Heater
The Westinghouse 14kW is best for buyers who want a compact electric unit with app and voice-control features. The listing specifies 3.4 GPM when inlet water is 62°F and the outlet is set to 105°F, with support for two water points under those conditions. It also lists a 0.53 GPM minimum startup flow and 98% thermal efficiency.
Wi-Fi features include temperature adjustment and usage monitoring through an app, compatibility with Alexa and Google Home, and temperature memory after a power outage. Check the electrical requirements: the product calls for 240V, a dedicated 60A double-pole breaker, and 6 AWG wire. Its listed flow is conditional, not a promise of the same output in every climate.
Buying Guide: How To Choose A Tankless Water Heater
Should you choose gas or electric?
Start with the fuel available and the home’s existing capacity. Natural gas models are represented here by higher listed whole-house flow options, while electric models require careful review of voltage, breaker, and wiring specifications. A licensed professional can assess whether a planned installation fits the home’s gas or electrical service.
How much flow rate do you need?
Estimate how many showers and appliances may run at the same time. Compare product flow rates at their stated temperature rises or inlet-water conditions, not just the largest number on a listing. Colder incoming water generally means the heater must raise the temperature further, which can affect delivered flow.
Does installation location matter?
Yes. Confirm whether the chosen product is designed for indoor or outdoor installation and review its venting and connection requirements. The Rheem and Rinnai models listed here are indoor units; the NOVIEEX and Westinghouse are electric models. Have installation requirements confirmed before ordering.
Which features are worth comparing?
Compare temperature controls, low-flow activation, diagnostic displays, efficiency figures, and smart features only when they match your priorities. Confirm included versus separately sold accessories, and read the complete product documentation for installation and maintenance requirements. The figures in this comparison come from the supplied product descriptions and do not establish independent rankings or customer ratings.
Frequently Asked Questions
What does a tankless water heater do?
It heats water on demand rather than storing a tank of hot water. The heater’s output must be matched to the home’s simultaneous hot-water needs.
Can a tankless heater run multiple showers?
Some models list support for multiple fixtures, but actual performance depends on flow demand and the temperature rise required. Check the model’s conditions and consult an installer.
Is a higher GPM always better?
No. GPM is useful for comparison, but the listed rate may depend on incoming water temperature and temperature rise. Electrical or gas capacity and household demand also matter.
Do electric tankless heaters need a dedicated circuit?
Requirements vary by model. The NOVIEEX and Westinghouse listings specify substantial dedicated electrical provisions, so verify the exact requirements with a qualified electrician.
Does “highest rated” mean the same as highest flow?
No. A rating typically refers to customer or expert evaluations, while GPM measures stated water-flow capacity. The product information provided here does not include ratings, so compare specifications rather than assuming a rating position.