Best Electric Continuous Water Heaters for on-Demand Hot Water
On-demand or continuous hot water is a core feature for many homes, especially in busy environments where hot water is needed at multiple points simultaneously. The following selections represent reliable electric tankless heaters offering fast hot water, energy efficiency, and smart options for modern households. Each unit is evaluated for flow potential, electrical requirements, and ease of installation to help you compare profiles side-by-side.
| Product | Brand | Type | Key Benefit |
|---|---|---|---|
| Rheem RTEX-24 24kW | Rheem | Tankless Electric | High flow with robust 24 kW capacity |
| Rheem 18kW 240V | Rheem | Tankless Electric | Compact, reliable on-demand heat |
| EcoSmart ECO 11 | EcoSmart | Tankless Electric | Self-modulating efficiency in a small form |
| Westinghouse APOLO-14kW | Westinghouse | Smart WiFi Tankless | Remote control and reliable offline water heating |
| Orbek 18kW | Orbek | Tankless Electric | High efficiency with rapid on-demand hot water |
Rheem RTEX-24 24kW Tankless Electric
Rheem’s RTEX-24 is designed for whole-home continuous hot water with a 24 kW output. It requires a substantial electrical setup: three 40-amp double-pole breakers and a 200-amp service recommended, with 240V operation. The unit is rated for continuous hot water, though real-world output depends on groundwater temperature and installation location. The model features an ON/OFF dial and adjustable digital temperature display, allowing precise control from 80 to 140 degrees Fahrenheit in 1-degree increments. Installation space inside the breaker panel and adequate power supply are critical considerations for this unit. Its performance is best evaluated against your geographic water temperature profile to ensure adequate gallons per minute for your household usage.
Rheem 18kW 240V Tankless Electric
This Rheem 18kW model offers an external digital thermostatic control with LED readout for precise temperature management. It employs the most advanced self-modulation to adjust heat output to match hot water demand, helping conserve energy. It includes durable copper immersion heating elements and is designed to be field serviceable. Typical flow rates reach up to 4.4 GPM, making it suitable for smaller homes or spaces where a single bathroom is used at a time. The unit emphasizes reliability and straightforward troubleshooting, with a focus on consistent performance at moderate flow requirements.
EcoSmart ECO 11 Electric Tankless Water Heater
EcoSmart’s ECO 11 uses patented self-modulating technology and is designed for energy efficiency and space savings. At 13 kW, it’s a compact 11-inch model suitable for point-of-use installations, including under sinks or small bathrooms. It can deliver on-demand hot water with a flow rate suitable for a single point of use at a time, and it’s touted as 90% smaller than traditional tank heaters. The device is 99% energy efficient because it heats water only when needed. A notable feature is its flexibility in mounting locations and a compact footprint for tight spaces, with a measured 11.5 x 8 x 3.75 inches footprint when installed.
Westinghouse APOLO-14kW Smart WiFi Tankless
The APOLO-14kW from Westinghouse provides continuous hot water with an emphasis on smart features, including compatibility with Alexa and Google Home for remote operation. It is rated at 14 kW with an amperage around 59A and supports a 60-amp DP breaker with a 6 AWG wire. The unit features a 0.5 GPM activation flow and is designed to supply simultaneous use—for example, one shower and one sink—without temperature fluctuations. The LED display enables easy real-time monitoring of performance, streamlining installation and daily use in a connected home environment.
Orbek 18kW Tankless Electric
Orbek’s 18kW tankless heater claims rapid on-demand hot water for 2-3 fixtures, requiring 2 x 240V/40A two-pole breakers and 3/4″ NPT water connections. The setup assumes a household service of at least 150 amps to avoid overloading the panel. The unit focuses on energy efficiency and fast response, with claims of delivering hot water in as little as three seconds. It’s positioned for households seeking to maximize simultaneous use across multiple fixtures while maintaining stable temperatures. Practical installation requires assessing existing electrical capacity and panel space before purchase.
XWDZSWGS 110V Tankless Water Heater
This 110V under-sink model delivers up to 3,000W of instantaneous hot water with LED display and a Fahrenheit/Celsius conversion option. It’s designed for compact spaces and is not recommended for showers due to its limited GPM, making it better suited for point-of-use applications like a sink or small bathroom. The unit emphasizes safety features such as water-electric separation and IPX4 waterproofing, with automatic power-off in cases of overheating or inactivity, promoting energy efficiency and safety in tight installations.
ThermoMate 27kW On-Demand Tankless Heater
The ThermoMate 27kW heater draws a maximum of 114 Amps and requires three dedicated double-pole 40A circuit breakers, typically paired with a 200A service for stable operation. It offers instant hot water with a flow rate of 5.27 GPM at a 35°F rise, making it capable of supporting multiple fixtures simultaneously. The unit uses self-modulating technology to adjust energy usage according to demand, delivering efficiency while maintaining comfort. Its wall-mounted design provides a space-saving solution for residential indoor showers and similar applications.
Buying Guide: Key Purchase Considerations
- Electrical capacity and service: Many high-capacity units require 200A service and multiple dedicated breakers. Verify your electrical panel can accommodate the load before purchase.
- Flow rate needs: Determine the GPM you need at peak usage (e.g., shower + sink). Tankless heaters vary widely in GPM at different temperature rises.
- Temperature rise and location: Groundwater temperature impacts performance. Cooler climates may need higher kW units or staged installations to maintain comfort.
- Self-modulating technology: Many models use self-modulation to save energy. Compare installation space, efficiency claims, and real-world performance.
- Remote and smart controls: Some units include Wi-Fi, app, or voice-control features. Consider whether smart capabilities fit your home ecosystem.
- Size and installation: Tankless heaters are compact but require proper venting-free electrical access. Check space, mounting options, and water connection orientation.
- Maintenance and serviceability: Field-serviceable components and copper immersion elements can simplify repairs and extend the unit’s life.
- Electrical compatibility with other appliances: Ensure the chosen unit won’t overload circuits when other high-power devices are operating simultaneously.