10 Best Compact Tankless Electric Hot Water Heaters 2026 in the United States

The EcoSmart ECO 11 is a compact and efficient tankless electric water heater designed mainly for small applications like a bathroom, office sink, or breakroom. It delivers a flow rate between 1.3 and 3.1 gallons per minute, which is suitable for low-flow needs but won’t support multiple large water outlets simultaneously. Its 13,000-watt power rating and 240-volt operation enable it to heat water consistently with a temperature control accurate within 1 degree, reaching up to 140°F. One of its standout features is the patented self-modulating technology, which adjusts energy use based on your hot water demand, making it very energy efficient at about 99%, and helping you save on electricity bills.

The unit is also notably small—about 11.5 by 8 inches—and wall-mounted, saving valuable space compared to traditional tank heaters. Installation is straightforward for point-of-use situations, but because it draws 54 amps, your electrical system must be compatible and may need professional setup. The ECO 11 includes a lifetime warranty on the electronics and heating elements, which adds peace of mind, though labor costs aren’t covered.

Due to its limited flow rate, this model is best suited for single fixtures rather than whole-house use, and the relatively high amperage requirement can complicate installation in some homes. For those needing a compact, energy-saving unit for small or occasional hot water needs, this product provides reliable and consistent performance with easy temperature control.

The Rheem RTEX-36 is a powerful electric tankless water heater designed for indoor wall mounting. It delivers up to 6 gallons per minute, sufficient to supply hot water for multiple fixtures at once in moderate-sized homes. With a 36 kW power rating and 240V voltage, it can provide a strong temperature rise, heating water quickly and efficiently. Its energy efficiency is excellent at 99.8%, meaning very little energy is wasted during operation, which can help save on electricity bills over time. The unit features digital temperature control, allowing you to set your preferred water temperature precisely for added convenience and comfort. It has a compact and sleek silver design, but is fairly heavy at around 24 pounds and needs to be hardwired with a 240V power supply, so professional installation is recommended.

The size is manageable for most indoor utility spaces, but you’ll want to ensure your electrical system can support its power needs. Customer feedback highlights its reliability and strong performance. This model may be more suitable for users with moderate to high hot water demand rather than very small households or low-demand applications due to its higher power and flow capabilities. The RTEX-36 is ideal for those seeking an energy-efficient tankless heater capable of handling multiple water outlets simultaneously, provided they have the appropriate electrical setup and installation space.

The EcoSmart ECO 18 is a compact electric tankless water heater designed for residential use in moderate climates where incoming water temperatures are around 62°F or higher. It offers a power rating of 18 kilowatts at 240 volts, which is quite strong for its size (14" x 17" x 3.5") and enables it to provide a maximum flow rate of about 3.5 gallons per minute. This means it can comfortably supply hot water for one or two fixtures simultaneously, such as a bathroom sink and a shower, but might not be enough for larger households needing multiple hot water sources at once.

One of its convenient features is the digital temperature control with 1-degree increments, allowing precise adjustments for comfort. The patented self-modulating technology helps maintain energy efficiency at an impressive 99.8%, which can help reduce electricity costs compared to traditional water heaters. Installation is relatively straightforward due to its compact design, though it requires a 240-volt electrical connection and is best suited for homes with compatible wiring. The unit comes with a lifetime warranty on electronics, exchanger, and heating element, which offers good peace of mind, although the warranty does not cover labor costs or incidental damages.

A drawback is that it’s optimized for warmer incoming water and may struggle in colder climates without additional units or pre-heating, limiting its versatility. The EcoSmart ECO 18 serves as a solid choice for small households or point-of-use scenarios looking for energy-efficient, on-demand hot water in a compact form.