10 Best Electric Tankless Water Heater 2025 in the United States

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 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 Tempra 15 Plus is a compact and efficient electric tankless water heater suited for those looking to save space while getting continuous hot water. It offers a power rating of 14.4 kW on 240 volts, which is good for providing hot water in small to medium households. The advanced flow control technology helps maintain a steady water temperature by slightly adjusting the flow when demand is very high, so you usually won’t experience sudden temperature drops during showers. Temperature output ranges from 68° to 140°F, covering most household needs, though the actual temperature rise depends on your starting water temperature and flow rate.

This model requires a minimum 100-amp electrical service, which might mean an upgrade to your home’s electrical system if you don’t already have it. Its sleek wall-mounted design is easy to install without venting, making it suitable for homes with limited space. Energy efficiency is a strong point here, as the unit auto-modulates power use based on demand and includes an energy savings monitor to help track costs. The digital display and memory presets make operation straightforward and user-friendly, even if you’re not tech-savvy.

Despite the flow control aiding temperature consistency, the unit’s capacity might struggle to meet very high simultaneous hot water demands, such as multiple showers running at once. Also, the initial electrical requirements could add to installation costs. The included 7-year leakage and 3-year parts warranties add peace of mind. The Tempra 15 Plus is a reliable, energy-saving choice for those wanting endless hot water without taking up much space, best suited for users with moderate hot water needs and adequate electrical service.