Reader support keeps this site open, opinionated, and happily independent. As an Amazon Associate, I earn from qualifying purchases.7 Best 80 Gallon Electric Water Heater | Smart 36kW Tankless

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The Rheem RTEX-36 delivers a tested 140°F output in cold climates, matching the demands of a large household that previously relied on a traditional storage tank. With a 99.8 percent efficiency rating and brass and copper construction, this unit eliminates the standby heat loss that plagues conventional 80-gallon tanks. Reviewers consistently note that it heats water significantly hotter than competing brands, which is crucial for maintaining adequate temperature at distant fixtures.

Real-world feedback from owners replacing two failing Ecosmart units highlights the Rheem’s superior heating performance and higher flow rate. The external adjustable temperature control and 3/4-inch NPT connections make installation straightforward, though the unit requires a 240V supply and adequate breaker capacity. Users report a slightly longer wait for hot water compared to a tank, but the endless supply and elimination of leak risk are compelling trade-offs.

This model is a solid choice for anyone who values proven reliability and high-temperature output. The compact wall-mount design frees up floor space, and the 6 GPM flow rate comfortably serves a 2,500-square-foot home. For the performance per dollar, this is the benchmark that other tankless units are measured against.

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The WINTEMP WM36V Plus stands out with a generous 8.7 GPM flow rate and full WiFi control via the Smart Home and Tuya Smart app. This allows you to monitor real-time water flow, track energy usage, and adjust temperature between 86°F and 140°F remotely — a feature that brings modern convenience to the category. The all-steel housing and internal cast-aluminum heating system give it a premium, durable feel that owners praise as “heavy and well-made.”

Advanced flow control technology automatically maintains water temperature by slightly reducing flow when demand exceeds capacity, preventing cold blasts during simultaneous usage. Owners report running the washer, dishwasher, and a shower simultaneously with no temperature fluctuation, even with incoming water temperatures as low as 50-60°F. The unit requires 4 x 40 Amp double-pole breakers and 8 AWG wiring, consistent with other 36kW models.

The ETL certification and multiple safety protections — including leakage, overheat, and dry-fire protection — provide peace of mind. While the unit lacks a UL certification logo that some buyers expect, the solid construction, clear instructions, and responsive customer support make this a compelling mid-range option. The two-year warranty adds an extra layer of confidence.

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The Stiebel Eltron Tempra 36 Plus represents German engineering in the tankless water heater space, featuring an exclusive Advanced Flow Control system that self-modulates power to maintain a consistent output temperature. The digital display provides accurate temperature readouts, and the compact footprint measures just 16.63 by 14.5 inches. This unit is designed for homes with high demand, supporting up to four bathrooms according to long-term owners.

A 14-year replacement cycle from one reviewer underscores the build quality — the previous Stiebel unit ran reliably for nearly a decade and a half before being swapped for this newer model. The 36kW output requires three 50-amp breakers, which is a higher amperage requirement compared to other units that use four 40-amp breakers. Owners consistently report excellent hot water production within one to two minutes, significantly faster than traditional tanks.

One caveat is that the unit’s performance depends heavily on proper electrical installation. A few reviewers experienced inconsistent temperature or long wait times, which were linked to insufficient breaker configuration or wiring issues. When properly installed with adequate 6 AWG wiring and all three breakers functioning, the Tempra 36 Plus provides reliable, endless hot water with the precision of German manufacturing.

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The Ecosmart ECO 36 has built a reputation for long-term reliability, with multiple owners reporting four years or more of trouble-free operation. This unit features a digital output temperature display and a sleek, compact design that mounts easily on any wall. The 99.8 percent energy efficiency rating means nearly all the electricity consumed goes directly into heating water, with zero standby loss.

Installation requires four double-pole 40A circuits, which occupies eight slots in your breaker panel. Owners in cold climates report that the unit handles one shower flawlessly in Ohio winters and can manage two showers simultaneously during warmer months. The ability to adjust the output temperature down to 80°F is a handy feature for tasks like washing cars or filling fish tanks without mixing with cold water.

A critical point to note is the warranty registration requirement — the unit must be registered within 30 days of purchase. Several owners who missed this window encountered difficulties with customer support. Despite this, the ECO 36 remains a solid mid-range workhorse with a limited lifetime warranty when registered properly, making it a dependable choice for families seeking endless hot water.

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The Stiebel Eltron Tempra 29 Plus offers a slightly more power-efficient alternative at 28.8kW while still providing an endless supply of hot water for most households. Its standout feature is the dual temperature memory presets, which allow you to store two personalized temperature settings — ideal for switching between a hot shower temperature and a lower setting for filling a bathtub. The unit is made in Germany and shares the same premium build quality as its 36kW sibling.

Owners report that the unit supplies endless hot water for families of six, filling baths without waiting for a tank to reheat. The on-demand design eliminates standby power consumption entirely, and users have documented annual savings. The installation requires three dedicated 40-amp breakers with 8 gauge copper wiring and a minimum 200-amp total service to the home, which is slightly less demanding than the 36kW models.

A common point of feedback is that the mounting holes are spaced 15 inches on center, which doesn’t align with standard US stud spacing, so additional mounting hardware may be needed. The hinged front cover can also limit access in tight closet installations. Despite these minor quirks, the Tempra 29 Plus delivers reliable performance with the precision temperature control that Stiebel Eltron is known for.

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The Rheem RETEX-36 Performance model is a self-modulating unit that automatically adjusts its power output based on real-time water flow and temperature, which helps reduce energy consumption when demand is low. Despite being listed as a refurbished product, it offers a cost-effective entry point into tankless water heating without sacrificing the Rheem brand’s reputation for reliability. The unit measures just 21.62 by 18.25 inches and weighs 19 pounds, making it one of the more compact options available.

Owner reviews highlight the unit’s compact size and instant heating capability, along with the convenience of easy temperature control. The self-modulating feature is a significant advantage for energy-conscious buyers, as it prevents the unit from running at full power when only one faucet is in use. However, some buyers received units that appeared used rather than properly refurbished, and the electrical draw — requiring multiple circuits — was a surprise for those unfamiliar with tankless requirements.

This unit is best suited for budget-conscious buyers who are comfortable with refurbished electronics and have the necessary electrical infrastructure. The self-modulating functionality provides genuine energy savings, and the compact form factor makes installation possible in tight spaces. Be prepared to inspect the unit upon arrival, as quality control on refurbished units can vary.

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The A. O. Smith ATI-310CX3 is a gas-powered tankless unit that delivers an impressive 8 GPM flow rate, making it a direct competitor to electric tankless models for whole-house use. Its X3 Scale Prevention Technology is a unique feature that reduces mineral buildup without requiring annual descaling or isolation valves — a significant maintenance advantage, especially in areas with hard water. The commercial-grade copper heat exchanger provides 25 times better heat transfer compared to steel, ensuring efficient operation.

This unit achieves a Uniform Energy Factor (UEF) of up to 0.81, translating to lower energy costs compared to older gas tank models. The included propane conversion kit makes it versatile for homes using either natural gas or propane. Owners report that the unit maintains a constant 115°F temperature even when multiple fixtures are running, and the built-in scale prevention filter reduces maintenance demands considerably.

Professional installation is strongly recommended due to gas line requirements and venting considerations. The direct vent APNC35 concentric vent system simplifies termination, but the unit’s 51-pound weight and 190,000 BTU output mean it needs a proper 3/4-inch gas line. This is an excellent option for those who prefer gas heating and want to avoid the high electrical demands of electric tankless units, but it requires a gas line connection that may not be available in all homes.