If you are searching for tankless water heaters from 2015, note that the product information available here does not establish which models were released that year. The five listed options can instead be compared by fuel type, stated flow rate, and installation requirements. The MIZUDO is best suited to higher-demand households, while the ThermoMate offers a lower-capacity natural-gas option. For electric systems, the 18kW model targets several fixtures, and the Rheem 8kW is better suited to more modest demand.
| Product | Fuel | Stated capacity | Best suited for |
|---|---|---|---|
| MIZUDO 199,000 BTU | Natural gas | Up to 10.3 GPM | Higher whole-house demand |
| ThermoMate CZ422NG | Natural gas | Up to 5 GPM | Moderate demand and two showers under stated conditions |
| 18kW Tankless Heater | Electric | Up to 3–4 usage points, per listing | Multiple electric hot-water draws |
| Westinghouse 14kW | Electric | Up to 3.4 GPM under stated conditions | Smart-home features and modest simultaneous demand |
| Rheem 8kW | Electric | Up to 1.95 GPM | Lower hot-water demand |
MIZUDO 199,000 BTU Natural Gas Heater
The MIZUDO is best for households with several simultaneous hot-water demands. Its listing specifies 199,000 BTU of heating input and up to 10.3 GPM, with support for demand across two to three bathrooms, kitchen faucets, laundry, and dishwashers. Those are manufacturer-listed capacities, not a guarantee of a particular flow rate in every home.
The unit has a stated temperature range up to 149°F and temperature control within ±1°F. Its 0.53 GPM low-flow activation is intended to let the heater respond to lower-flow draws. The listing describes reduced standby heat loss compared with a traditional tank.
- Best for: Larger households comparing high-capacity natural-gas options.
- Why it stands out: It has the highest stated flow rate among these five products.
- Consideration: Confirm that the home’s gas supply, venting, and installation conditions meet the unit’s requirements; those details are not provided in the listed features.
ThermoMate CZ422NG Natural Gas Heater
The ThermoMate CZ422NG is best for buyers seeking a natural-gas indoor model with a stated maximum flow below the MIZUDO’s. It is rated up to 5 GPM and 113,000 BTU. The listing says it can supply two showers at the same time while maintaining 105°F when inlet water is 65°F. Actual capacity depends on incoming water temperature and simultaneous demand.
Listed features include a copper heat exchanger, up to 98% thermal efficiency, and a UEF of 0.81. The product description also lists multiple safety protections, including freeze protection that activates at 41°F (5°C), and CSA certification. The stated temperature consistency is ±1°F.
- Best for: Homes that want gas-fired on-demand hot water and have moderate simultaneous demand.
- Why it stands out: Its stated two-shower performance is tied to a specific inlet-temperature condition.
- Consideration: Do not assume the two-shower claim applies in colder inlet-water conditions or at every flow setting.
18kW Electric Tankless Water Heater
This 18kW electric model is best for buyers who want a compact heater intended to serve several usage points. The listing describes it as suitable for three to four simultaneous points and states up to 99.8% thermal efficiency. It also specifies a 240V supply, two 40-amp circuit breakers, and standard 3/4-inch NPT water connections.
The manufacturer describes the unit as having no preheating or idle power use and says its design eliminates standby energy loss. These are product claims; actual energy use and hot-water performance depend on household use, incoming water temperature, and electrical installation.
- Best for: Buyers comparing a higher-power electric option for multiple hot-water draws.
- Why it stands out: The listing specifies its breaker arrangement and connection size, useful details for early installation planning.
- Consideration: Verify that the home can support the required 240V electrical circuit before choosing this model.
Westinghouse 14kW Wi-Fi Electric Heater
The Westinghouse 14kW is best for buyers who value app-based controls and have electrical capacity for its stated installation requirements. The listing calls for a dedicated 60A double-pole breaker and 6 AWG wire at 240V. It has 1/2-inch NPT connections and a compact wall-mountable form, with listed dimensions of 12.59 by 9.56 by 3.28 inches.
Its stated maximum flow is 3.4 GPM when inlet water is 62°F and the outlet is set to 105°F; the listing says this supports two water points under those conditions. Features include Wi-Fi, Alexa and Google Home compatibility, temperature memory, and a minimum startup flow of 0.53 GPM.
- Best for: Smart-home users with modest simultaneous hot-water needs.
- Why it stands out: It combines voice and app controls with a stated flow rate tied to defined temperature conditions.
- Consideration: Check the dedicated circuit and wire requirements before purchase, and do not treat the 3.4 GPM figure as universal.
Rheem 8kW Multi-Fixture Electric Heater
The Rheem 8kW is best for lower-demand applications where a stated maximum of 1.95 GPM may be sufficient. The listing identifies it as a 240V electric heater for multiple fixtures and advises buyers to choose the right size and verify electrical requirements before installation.
Like other electric tankless units, it heats water on demand and can save space compared with a storage tank, according to the product description. Its lower stated flow makes it a different choice from the 14kW and 18kW electric models in this comparison.
- Best for: Buyers with limited simultaneous hot-water demand who are considering an electric unit.
- Why it stands out: It provides a clear 1.95 GPM capacity figure for comparison.
- Consideration: A flow rate of up to 1.95 GPM may not meet demand for several high-flow fixtures at once.
Buying Guide: How to Choose a Tankless Water Heater
Does the “2015” search term mean you need a model released in that year?
Check the model’s documentation or manufacturer information for a release date. The product details above do not confirm that any listed heater was released in 2015. If you need a replacement for a system installed around that time, match the new unit to your current fuel source, household demand, and installation setup rather than relying on the year alone.
How much hot water do you need at once?
List the fixtures that could run at the same time, such as a shower, kitchen faucet, and dishwasher. Compare their combined flow demand with the heater’s capacity under the expected inlet-water temperature and desired outlet temperature. A product’s maximum GPM does not mean it will deliver that rate in every climate or at every temperature setting.
Among these options, the MIZUDO has the highest stated flow at up to 10.3 GPM. The ThermoMate lists up to 5 GPM under its stated conditions. The electric listings provide different capacities: up to 3.4 GPM for the Westinghouse under specified temperatures and up to 1.95 GPM for the Rheem. The 18kW listing describes three to four usage points but does not provide a GPM figure in its supplied features.
Should you choose gas or electric?
Start with the fuel and utilities already available at the installation location. Gas models require suitable gas service and venting; electric models require electrical circuits that meet their stated voltage, breaker, and wiring needs. A high-capacity heater is not a practical choice if the home cannot support its installation requirements.
Natural-gas options in this comparison include the MIZUDO and ThermoMate. Electric options include the Westinghouse, Rheem, and 18kW model. Have a qualified installer assess the home’s supply and installation conditions before selecting a unit.
What electrical details should you check?
Compare the heater’s voltage, circuit-breaker requirements, and wire requirements with the home’s electrical service. The Westinghouse listing specifies 240V, a dedicated 60A double-pole breaker, and 6 AWG wire. The 18kW listing specifies 240V and two 40-amp breakers. The Rheem listing advises verifying electrical requirements but does not provide them in the supplied features.
Which features matter beyond capacity?
- Temperature control: The MIZUDO and ThermoMate list temperature consistency of ±1°F.
- Smart controls: The Westinghouse lists app control, Alexa and Google Home compatibility, and temperature memory.
- Low-flow activation: The MIZUDO and Westinghouse list activation at 0.53 GPM.
- Safety and certification details: The ThermoMate listing describes several protections and states CSA certification.
- Physical connections: Compare the stated water-connection size with the planned installation.
How should efficiency claims affect your choice?
Efficiency figures use different measures and should not be treated as direct substitutes. The ThermoMate lists up to 98% thermal efficiency and a UEF of 0.81; the Westinghouse lists 98% thermal efficiency; and the 18kW model lists up to 99.8%. Consider the measurement provided, your expected water use, and installation requirements. Claims about potential savings are not guarantees of a particular household’s bill reduction.
Frequently Asked Questions
Are any of these products confirmed as 2015 models?
No. The supplied product information does not identify release years, so it cannot confirm that any listed heater is a 2015 model.
Which listed heater has the highest stated flow rate?
The MIZUDO lists up to 10.3 GPM. This is a stated maximum, and actual flow depends on water temperature and installation conditions.
Which option is best for a smaller hot-water demand?
The Rheem 8kW may suit lower demand because its listing specifies up to 1.95 GPM. Compare that capacity with the fixtures you expect to use at the same time.
Can the ThermoMate supply two showers at once?
Its listing says it can supply two showers at 105°F with 65°F inlet water. Colder inlet water or greater demand may affect performance.
What should I verify before buying an electric tankless heater?
Confirm the required voltage, breaker arrangement, wire size, and available electrical capacity. The Westinghouse and 18kW listings specify particular circuit requirements that should be checked before installation.