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Best Electric Tankless Water Heater

3 expert-curated picks ranked by performance, value, and long-term reliability

Electric tankless is a specific tool for a specific job. It works extremely well for the right household in the right climate and works poorly outside that envelope. The picks here cover the three buyer scenarios where electric tankless actually delivers what is promised — and we note one scenario where the answer is to choose something else entirely.

Best for whole-house electric tankless

Best in Sun Belt climates (groundwater above 60°F): Rheem RTEX-18

18 kW, two 40-amp double-pole breakers, pulls 75 amps on a single feed. Delivers about 3.0 GPM at a 40°F rise — enough for one shower plus a kitchen tap in southern climates year-round. Lifetime warranty on the heat exchanger, 5-year warranty on electronics. Self-modulates in 0.5 kW increments. Fits in most 200A panels and many well-loaded 100A panels after a competent load calc. About $549 unit, $1,400 installed.

Best in northern climates (groundwater 40–50°F): EcoSmart ECO 27

27 kW, three 40-amp double-pole breakers, requires 200A service. Pulls 112.5 amps across three feeds. Delivers about 3.0 GPM at a 60°F rise — workable for a single shower at a time in any US climate, comfortable for a southern 2-bath home. Lifetime warranty on both heat exchanger and electronics (the only major brand offering lifetime electronics in this category). Stainless steel heat exchanger handles harder water than copper-exchanger competitors. About $629 unit, $1,800 installed.

Best for point-of-use installs: EcoSmart POU 6

6 kW unit designed to feed a single fixture — a remote bathroom sink, a workshop utility sink, a wet bar. Mounts under a vanity, pulls from a 30A 240V circuit. Eliminates the long run of hot-water pipe from the main heater to a distant fixture. About $200 unit, $400–$700 installed depending on whether the electrical run is new.

Read this before buying

Whole-house electric tankless is the most-mis-bought category in water heating. The product works exactly as advertised; the problem is sizing it correctly against your existing electrical service. Specifically:

  • 100A service homes: the Rheem RTEX-18 may fit after load calc, but only if your home doesn't have an electric range, dryer, and air handler all running simultaneously. The math is tight. The ECO 27 cannot fit at all.
  • 200A service homes: ECO 27 fits cleanly. RTEX-18 fits with substantial headroom.
  • Service upgrade required: if you need to go from 100A to 200A specifically to support tankless, add $2,500–$4,500 to the project. That math rarely beats keeping a tank heater or adding a heat-pump.

The honest answer for many would-be electric tankless buyers in cold climates with 100A service: don't. A heat-pump water heater (Rheem ProTerra) delivers continuous hot water with one-third the electric draw and works in any climate. The install footprint and cost are similar.

Brand-specific notes

Rheem RTEX series: the broadest US service network for electric tankless. Replacement parts at any Rheem dealer. Copper heat exchanger requires descaling every 9–12 months in hard water.

EcoSmart: direct-to-consumer brand with the most generous warranty in the category. Customer service ships parts directly to homeowners. Stainless heat exchanger needs descaling every 18–24 months in hard water — half as often as copper-exchanger competitors.

Stiebel Eltron Tempra series: German engineering, premium pricing. Tempra Plus 24 and Tempra 36 deliver excellent low-flow modulation and quiet operation. Service network is thin in the US. About $850–$1,400 for the unit alone.

Bosch Tronic: the budget end of the European-engineered category. Reliable but small US service network. Their mini-tank line (Tronic 3000T) addresses point-of-use better than their whole-house line.

3 products
$949 – $1,795
Updated May 2026

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