10 Best high efficiency tankless electric hot water heaters 2026 in the United States

The Rheem RTEX-24 24kW 240V Electric Tankless Water Heater offers an impressive flow rate of up to 5.9 gallons per minute (GPM), which is quite strong for most household needs. Its self-modulating power control ensures efficient energy use by adjusting power based on hot water demand, contributing to its notable 99.8% energy efficiency.

The adjustable digital temperature display with an ON/OFF dial control makes it user-friendly, allowing for precise temperature adjustments and easy monitoring. Installation should be straightforward with its compact size (17.63”W x 18.25”H x 3.5”D) and wall-mount design, although professional installation is recommended due to the 24kW power requirement and 240V voltage. The unit's weight of 17.8 pounds is manageable for most installation scenarios.

Durability is supported by the stainless steel finish and robust build. The maximum water pressure of 150 PSI should be checked against your home’s water pressure to ensure compatibility. This heater is well-suited for homeowners looking for an efficient, high-performing solution to provide continuous hot water on demand.

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.