10 Best Electric Tankless Water Heater 2026 in the United States

The Rheem 18kW 240V Tankless Electric Water Heater is a solid choice for those looking for an efficient and space-saving water heating solution. One of its standout features is the impressive flow rate of up to 4.4 gallons per minute (GPM), which makes it suitable for smaller households or apartments where demand for hot water isn't excessively high. Its energy efficiency rating of 99.8% is quite remarkable, meaning you'll likely save on your energy bills compared to traditional tank heaters. The self-modulation technology adjusts the power based on hot water demand, which further optimizes energy use.

The external digital control with an LED display is user-friendly, allowing for precise temperature settings within a +/- 1-degree accuracy. This feature is particularly beneficial for those who want to maintain consistent hot water temperatures. The installation is straightforward as well, with bottom connections that make it easier to replace or service when needed.

There are a few drawbacks to consider. While the 4.4 GPM flow rate is adequate for smaller setups, larger families or homes with multiple bathrooms may find it insufficient during peak usage times. Additionally, being an electric unit, it may not be the best option for locations where electricity supply is unreliable or insufficient to support its high wattage of 18,000 watts. Lastly, while the unit is compact, its installation does require adequate space and professional help, especially for wall mounting, which could be a consideration for DIY enthusiasts.

The Stiebel Eltron 239223 Tempra 29 Plus is a high-performing electric tankless water heater that provides an on-demand and continuous supply of hot water. It features a sleek, space-saving design and does not require venting, which makes it versatile for various home installations. This model has a maximum flow rate of 3 gallons per minute (GPM), making it suitable for households with moderate hot water needs.

Its power rating is substantial, operating at 28.8 kW, which ensures a quick temperature rise but also means it requires a significant electrical setup: 240-volt service, three dedicated 40 amp breakers, and at least 200 amp total service to the home. This could be a hurdle for some installations and might require professional electrical work to update the home's capacity.

The unit features two temperature memory presets, providing convenience for users with different hot water preferences. It also has a useful LED display for easy monitoring and adjustments. Energy efficiency is a highlight, as tankless systems generally save on energy compared to traditional tank heaters by only heating water as needed. Potential buyers should consider the installation requirements carefully. This unit is most beneficial for medium to large households that can support the electrical demands, and who are looking for a reliable, space-saving, and energy-efficient solution for their hot water needs.

The Rheem 8kW 240V Tankless Electric Water Heater is a compact and energy-efficient option for delivering on-demand hot water. With a flow rate of up to 1.95 gallons per minute, it works well for single fixtures like a bathroom sink or a small kitchen setup, but it might struggle to supply multiple outlets at once or larger households. Its 8-kilowatt power rating and self-modulating technology help manage energy use effectively, adjusting power based on your hot water needs, which can save on electricity bills compared to traditional tank heaters.

The adjustable digital temperature display with a simple ON/OFF dial control makes it easy to set and maintain your preferred water temperature, adding convenience and safety. Installation is straightforward thanks to its compact size (about 8 by 12 inches) and standard 1/2-inch water connections, making it suitable for wall mounting in tight spaces. However, because it runs on 240 volts and 8 kW, you’ll need to ensure your home’s electrical system can support it, and professional installation might be required.

Given its efficient and user-friendly design, this unit’s limited flow rate means it’s best suited for small to medium hot water demands rather than whole-home use. If you need a reliable, energy-saving electric tankless heater for limited use points, this Rheem model is a solid choice, but larger households should consider higher capacity models.