10 Best Whole House Tankless Electric Hot Water Heaters 2025 in the United States

The Rheem RTEX-24 is a solid choice for those looking to upgrade to a tankless electric hot water heater for their home. With a flow rate of up to 5.9 gallons per minute (GPM), it can efficiently provide hot water for multiple outlets simultaneously, making it great for medium-sized households. Its self-modulating power control ensures that you get just the right amount of energy needed for heating water, which contributes to its impressive energy efficiency rating of 99.8%. This means you can enjoy consistent, on-demand hot water without worrying too much about energy consumption.

One notable feature is its ON/OFF dial control paired with an adjustable digital temperature display, making it user-friendly. Installation is straightforward, as it is designed for wall mounting and comes with necessary fittings, although professional help might still be recommended for optimal setup. The compact size of the unit (17.63” W x 18.25” H) allows it to fit conveniently in smaller spaces.

While the flow rate is decent, it may struggle to meet the hot water demands of larger households with simultaneous usage in multiple bathrooms or kitchens. The 24 kW power requirement also means that proper electrical infrastructure is necessary; homes must have the right voltage and amperage to support this unit. Additionally, while the warranty coverage is decent, some users may prefer a longer guarantee for peace of mind.

The Stiebel Eltron Tankless Water Heater – Tempra 24 Plus is a robust option for homeowners looking for an electric solution to efficiently provide hot water on demand. With a flow rate of 4.0 GPM and the ability to maintain a temperature rise of up to 140°F, it can comfortably supply hot water for multiple outlets simultaneously, making it suitable for larger households. Its eco-friendly design incorporates advanced flow control technology, which adjusts the water flow to maintain a consistent temperature, ensuring that you won’t be left with a cold shower.

One of the standout features is its space-saving design. The unit is compact and does not require venting, which allows for flexible installation options. The digital display and preset temperature buttons make operation simple, even for those who may not be tech-savvy. Energy efficiency is a strong point, too, as the heater saves power through auto-modulation, and a savings monitor shows how much you’re saving on energy costs.

However, there are a few considerations to keep in mind. The Tempra 24 Plus requires a minimum electric service of 150 A, which may necessitate upgrades to your home's electrical system if it doesn't meet this requirement. Additionally, while the compact size is beneficial, it may not be suitable for very high-demand scenarios where multiple fixtures are used simultaneously at peak demand times. The warranty coverage is quite favorable, offering a 7-year leakage warranty and a 3-year parts warranty, which is reassuring for potential buyers. The Stiebel Eltron Tempra 24 Plus is a solid choice for those seeking an efficient and reliable tankless hot water heater that can provide endless hot water without the bulk of traditional systems.

The Stiebel Eltron Tempra 36 Trend is a solid choice for a whole-house tankless electric water heater, designed to provide continuous hot water without interruption. Its 36 kW power rating and ability to deliver water temperatures from 68°F to 140°F mean it can handle the needs of a typical household well, offering a good flow rate for multiple faucets or showers at once. The heater’s compact size and wall-mounted design help save space, and it doesn’t require venting, which simplifies installation in many homes.

It features energy-saving auto-modulation technology to adjust power use based on demand, contributing to energy efficiency and potentially lowering electric bills. The digital LED display is easy to read and allows precise temperature control, and the heater operates quietly, which is a nice comfort feature. However, it does require a substantial electrical setup—a minimum of 300 amps service at 240 volts—which may mean additional electrical work and cost for some homes.

The unit weighs 22.5 pounds and has solid copper heating elements, which are durable and support consistent performance. Warranty coverage is reassuring, with 7 years against leaks and 3 years for parts, reflecting confidence in its reliability. This heater suits households with high hot water demand and adequate electrical capacity, while those with smaller homes or limited electrical service might find it less practical. Installation should be done by a professional to ensure it meets electrical requirements and functions safely. If continuous, on-demand hot water and energy efficiency are priorities, this model is a dependable option worth considering.