10 Best high efficiency tankless electric hot water heaters 2025 in the United States

The Stiebel Eltron Tempra 36 Plus is a high-powered tankless electric water heater designed to deliver continuous hot water on demand. It operates at 27,000 watts with a maximum flow rate of 1.5 gallons per minute, which is suitable for smaller households or point-of-use setups but might be limiting if you need simultaneous hot water at multiple fixtures. Its advanced flow control and self-modulation technology help save energy by adjusting power use based on demand, making it a strong choice if you're looking to reduce utility bills.

The digital LED display allows for precise temperature control, which adds convenience and helps maintain consistent water temperature. Installation is straightforward with a floor mounting method, and the unit is relatively compact at about 17 by 14.5 inches, so it won’t take up much space. However, it requires a 208-volt power supply, which might need electrical upgrades in some homes. The product is well-reviewed for reliability and efficiency.

If you want an energy-efficient electric tankless heater for a smaller capacity setting and don’t mind the electrical requirements, the Tempra 36 Plus represents a solid, dependable option.

The Stiebel Eltron Tempra 29 Plus is a powerful, high-efficiency tankless electric water heater designed to provide continuous hot water on demand. It delivers up to 3 gallons per minute, which is suitable for a household with moderate hot water needs, like running one or two showers plus a sink at the same time. Its compact size (about 17 by 15 inches) helps save space and the sleek design means no venting is required, making installation flexible for many homes.

The unit has a strong 28.8 kW power output, meaning it can heat water quickly with a notable temperature rise, which is great if you live in colder climates and need a consistent hot water supply. An LED display and two temperature memory presets make it easy to set and save your preferred water temperatures. On the energy side, it’s very efficient, so it won’t waste electricity heating water when you don’t need it. However, this heater requires a substantial electrical setup: a dedicated 240-volt or 208-volt hard-wired connection, 3 separate 40-amp breakers, and at least a 200-amp main service panel. This means you might need professional electrical upgrades, which can add to installation cost and complexity.

The unit is relatively lightweight at 24 pounds and mounts on the wall, freeing up floor space. If you have a large household or very high hot water demands, you might find the 3 GPM flow limiting, but for many, it balances power, efficiency, and convenience effectively.

The Stiebel Eltron Tempra 29 Trend is a standout in the category of high-efficiency tankless electric hot water heaters, perfect for homeowners seeking an endless supply of hot water. Its continuous flow feature ensures that hot showers are never interrupted, which is a major plus for families or anyone who frequently uses hot water. With a power output of 28.8 kW, it quickly heats water between temperatures of 68°F and 140°F, catering well to varying needs.

One of its notable strengths is energy efficiency. This model is designed to save energy with its auto modulation feature, which adjusts the power usage according to demand, making it eco-friendly. Additionally, the compact size—16.63 inches wide and 14.5 inches high—allows for easy installation in tight spaces without the need for venting, which is a great space saver for modern homes.

The silent operation is another major advantage, as it operates quietly while in use, making it ideal for homes where noise is a concern. The digital temperature display is user-friendly and easy to read, adding to the convenience. The Tempra 29 Trend requires a substantial electric service of at least 200 A, which may not be feasible for all homes without an electrical upgrade. Although the warranties offered are generous—7 years for leakage and 3 years for parts—some users might find it a bit pricey compared to traditional water heaters, especially if they have lower hot water demands.