Best Electric Tankless Water Heaters (2026)

TL;DR

Top pick: Stiebel Eltron Tempra 36 Plus (~$789) — 36 kW, up to 7.5 GPM, Advanced Flow Control prevents cold-water sandwiching, ~99% efficient.
Best value: EcoSmart ECO 27 (~$420) — 27 kW, self-modulating, digital control, ~3 GPM in cold climates for far less than premium units.
Best budget: EcoSmart ECO 11 (~$207) — 13 kW, single 60A breaker, ideal for one bathroom or a warm-climate small home.

For mid-size homes, the Rheem RTEX-18 (~$446) and RTEX-24 (~$549) are the proven workhorses. [src1, src2]

The 2026 electric tankless market splits cleanly by power class. At the top, the Stiebel Eltron Tempra 36 Plus (~$789) is the consensus best overall: a 36 kW German-made unit with Advanced Flow Control that dynamically throttles water flow rather than dumping cold water when demand exceeds capacity — a smarter approach than rivals that simply cut output power [src1, src2, src3]. It is rated near 99% efficient and can supply roughly 7.5 GPM in warm climates (enough for several simultaneous fixtures), though that figure drops sharply where winter inlet water is cold [src1, src3]. For most buyers the value play is the EcoSmart ECO 27 (~$420), a 27 kW self-modulating unit with digital 1-degree temperature control that costs roughly half the premium tier while still heating ~3 GPM in cold climates and 6+ GPM in warm ones [src1, src5].

The mid and budget tiers are dominated by Rheem and EcoSmart. The Rheem RTEX-18 (~$446) and RTEX-24 (~$549) are the proven workhorses for 1-2 bath homes, with self-modulation, brass-topped replaceable heating elements, and a 99% efficiency rating [src1, src2]. The Rheem RTEX-13 (~$287) and EcoSmart ECO 11 (~$207) are point-of-use-to-small-home units that run on a single 60A breaker, ideal for a single bathroom, apartment, or warm-climate cabin [src1, src3]. The defining 2026 caveat across every unit is climate-driven sizing: GPM ratings are quoted at a modest temperature rise, and a heater that does 7.5 GPM in Florida may struggle to run one shower in Minnesota — buyers must size by winter inlet temperature, and whole-house 27-36 kW units often require a 200A panel and a costly service upgrade the sticker price hides [src1, src2, src6]. Self-modulating electric units can cut water-heating energy use 10-30% versus fixed-output models, and qualifying high-efficiency units may have been eligible for a federal tax credit — but 2026 eligibility should be verified before counting on it [src5, src6].

Best Overall: Stiebel Eltron Tempra 36 Plus (~$789) — Check price

The premium whole-home pick and the unit most reviewers crown best overall. Its 36 kW output and Advanced Flow Control set it apart: instead of letting cold water through when demand spikes, it intelligently reduces flow to hold your set temperature — eliminating the "cold-water sandwich." Nearly silent, ~99% efficient, with a digital display and auto-modulation. Made in Germany with a 7-year leak / 3-year parts warranty. Up to 7.5 GPM in warm climates. [src1, src2, src3]

Best Value: EcoSmart ECO 27 (~$420) — Check price

The cost-per-feature champion. A 27 kW self-modulating unit with digital temperature control in 1-degree increments and a compact 17 x 17 x 3.5 inch footprint. It heats ~3 GPM even where inlet water drops to 37°F and 6+ GPM in warm climates, covering most whole-home needs for roughly half the price of the Stiebel. EcoSmart claims up to 50% energy savings versus tank heaters and backs the heat exchanger with a lifetime warranty. [src1, src5]

Best Budget: EcoSmart ECO 11 (~$207) — Check price

The cheapest path to safe electric tankless hot water. A 13 kW unit that runs on a single 60A breaker, delivers ~3.1 GPM, and uses the same patented self-modulating technology as EcoSmart's larger units. Ideal for one bathroom, an apartment, an ADU, or a warm-climate small home where it can run a shower and a sink at once. [src1, src3]

Best for Condos / Small Spaces: Rheem RTEX-13 (~$287) — Check price

A compact 13 kW unit (about 12.6" x 8.25") that fits in a closet or cabinet and runs on a single 60A breaker. With ~3.17 GPM and 99% efficiency, it comfortably serves 1-2 simultaneous fixtures in a condo or small apartment, with a digital display and external dial control. The point-of-use-to-small-home sweet spot for Rheem. [src1, src3]

Best Mid-Size Workhorse: Rheem RTEX-18 (~$446) — Check price

The proven 1-2 bath solution. 18 kW, ~4.4 GPM, self-modulating, with durable brass-topped replaceable heating elements and a straightforward two-breaker install. Reviewers consistently cite it as the easy, reliable choice for a modest home that needs one or two showers' worth of capacity. 99% efficient. [src1, src2]

Best for 2-Bath Homes: Rheem RTEX-24 (~$549) — Check price

The step up when 18 kW isn't quite enough. 24 kW and ~5.9 GPM (warm-climate) let it run 2-3 fixtures, making it the practical pick for a two-bath home in a moderate climate. Same self-modulation and digital control as the rest of the RTEX line, with a three-breaker install. [src1, src2]

Best for Large Homes: Rheem RTEX-36 (~$650) — Check price

The highest-flow Rheem, a 36 kW unit rated up to ~8.8 GPM in warm climates — enough for four showers plus a faucet. It is self-modulating with an 80-140°F digital thermostat, but it demands serious electrical capacity (four 40A double-pole breakers) and typically a 200A panel. Reserve it for genuinely large, multi-bath households. [src1] (Sold mainly through plumbing-supply and home-improvement retailers; Amazon listing varies.)

Best Point-of-Use: Rheem RTEX-06T (~$189) — Check price

For a single sink, bathroom vanity, or remote fixture far from the main heater. A 6.5 kW unit delivering ~1.6 GPM on a single 240V circuit, with compact dimensions and precise temperature control. It will not run a shower in a cold climate, but it eliminates the long wait for hot water at a distant tap. [src2, src4] (Sold mainly through home-improvement retailers; Amazon listing varies.)

Head-to-Head Comparisons

Stiebel Eltron Tempra 36 Plus vs EcoSmart ECO 27

The Stiebel wins on intelligence and quietness — Advanced Flow Control prevents cold-water sandwiching and it edges the EcoSmart on real-world consistency. The EcoSmart wins decisively on price (~$420 vs ~$789) and offers a lifetime heat-exchanger warranty. Both are true whole-house units; the gap is ~$370 for smarter flow control. [src1, src5]

Pick Stiebel Tempra 36 Plus if: you want the smartest temperature stability, the highest flow, and best-in-class build quality.
Pick EcoSmart ECO 27 if: you want whole-house capacity at the lowest reasonable price and don't need Advanced Flow Control.

Rheem RTEX-18 vs EcoSmart ECO 27

The RTEX-18 (18 kW, ~4.4 GPM) suits a 1-2 bath home and installs on two 40A breakers; the ECO 27 (27 kW, ~6.6 GPM warm) handles a full house but needs three 40A breakers and more panel capacity. The Rheem is cheaper to install; the EcoSmart delivers more simultaneous-fixture headroom. [src1, src2]

Pick Rheem RTEX-18 if: you have a small-to-mid home, a tight panel, or want the simplest install.
Pick EcoSmart ECO 27 if: you need whole-house flow for multiple bathrooms and have the electrical capacity.

Rheem RTEX-13 vs EcoSmart ECO 11

Both are ~13 kW single-60A-breaker units for one bathroom or a small space. The Rheem RTEX-13 (~$287) is slightly higher flow (~3.17 GPM) with a more refined display; the EcoSmart ECO 11 (~$207) is the budget winner with the same self-modulating tech for ~$80 less. [src1, src3]

Pick Rheem RTEX-13 if: you want the more polished controls and slightly more flow.
Pick EcoSmart ECO 11 if: price is the priority and you want the cheapest safe whole-bathroom unit.

Stiebel Eltron Tempra 36 Plus vs Rheem RTEX-36

Both are 36 kW flagships. The Rheem RTEX-36 pushes the highest flow (~8.8 GPM warm) and is excellent for large multi-bath homes; the Stiebel wins on Advanced Flow Control, build quality, and quietness. Both need a 200A-class panel and heavy breaker capacity. [src1, src2]

Pick Stiebel Tempra 36 Plus if: you prioritize temperature stability and premium build.
Pick Rheem RTEX-36 if: you want maximum raw flow for the largest households at a lower price.

If budget is under $250

→ EcoSmart ECO 11 (~$207). 13 kW, single 60A breaker, self-modulating — the cheapest safe path to electric tankless hot water for one bathroom or a warm-climate small home. [src1, src3]

If you need whole-house hot water and want the best value

→ EcoSmart ECO 27 (~$420). 27 kW self-modulating, ~3 GPM in cold climates and 6+ GPM warm, for roughly half the price of premium flagships. [src1, src5]

If you want the best overall performance regardless of price

→ Stiebel Eltron Tempra 36 Plus (~$789). Advanced Flow Control eliminates cold-water sandwiching, ~99% efficient, up to 7.5 GPM, near-silent. [src1, src2, src3]

If you have a 1-2 bath home and a limited electrical panel

→ Rheem RTEX-18 (~$446) on two 40A breakers, or step up to Rheem RTEX-24 (~$549) for a true two-bath home. [src1, src2]

If you live in a cold climate (under 45°F winter inlet)

→ Oversize aggressively. A 27-36 kW unit (EcoSmart ECO 27 or Stiebel Tempra 36 Plus) is the floor for whole-house use; smaller units lose half their GPM at a 70°F temperature rise. [src1, src6]

If you only need hot water at one distant sink

→ Rheem RTEX-06T point-of-use (~$189). 6.5 kW, ~1.6 GPM — eliminates the wait at a remote tap without rewiring the whole house. [src2, src4]

Default recommendation (unknown requirements)

→ EcoSmart ECO 27 (~$420). Whole-house capacity, self-modulating efficiency, digital control, and a price most homeowners can justify. The safest pick when the user's home size and climate are unknown. [src1, src5]

• Climate-driven sizing is the #1 buyer mistake: GPM ratings are quoted at a modest (35°F) temperature rise. The same unit can lose half its flow at a 70°F rise — a heater that runs four showers in Florida may not run one in Minnesota. Always size by winter inlet temperature. [src1, src2]
• Self-modulation is now standard: nearly every quality electric unit (EcoSmart, Rheem RTEX, Stiebel) now varies power output to match flow, cutting water-heating energy use 10-30% versus old fixed-output designs. [src5, src6]
• Electric out-efficiencies gas at the unit: electric tankless units hit 98-99% efficiency versus 80-93% for gas, and need no venting — making them far easier and cheaper to install where adequate electrical capacity exists. [src1, src2]
• Panel capacity is the real cost driver: a 27-36 kW whole-house unit can draw 113-150A, often forcing a 200A panel or service upgrade ($1,000-$3,000+) that the wall-unit price hides. Sizing down or going point-of-use sidesteps this. [src1, src6]
• Federal tax-credit uncertainty: high-efficiency water heaters (UEF ≥ 0.95) were eligible for a 30% federal credit up to $600, but 2026 eligibility is in flux under recent legislation — verify before counting on it. [src5, src6]
• Long lifespan vs tanks: electric tankless units commonly last 20+ years versus 10-15 for storage tanks, improving lifetime value if hard water is managed with descaling or a softener. [src1, src2]

• Prices are approximate US street prices as of June 2026 and move with Amazon promotions; whole-house units in particular swing 10-25% on sales.
• Flow rate (GPM) is climate-dependent. Every headline GPM figure assumes a modest temperature rise; cold-climate buyers must size up substantially or accept lower simultaneous-fixture capacity. [src1, src2]
• Whole-house electric tankless heaters demand large dedicated 240V capacity (a 36 kW unit can need 150A). Many homes require a panel/service upgrade — budget for an electrician's load calculation before buying. [src1, src6]
• The Rheem RTEX-36, Stiebel Tempra 24 Plus, Thermomate 18kW, EcoSmart ECO 18, and Rheem RTEX-06T are set to search-link (no fixed Amazon ASIN) because they sell primarily through plumbing-supply and home-improvement retailers or the live Amazon listing varies; all other picks link to verified Amazon listings.
• Hard water shortens heating-element life. Plan on periodic descaling/flushing or a water softener; neglecting it causes early failure and can void the warranty. [src6]
• Federal tax-credit eligibility (UEF ≥ 0.95, equipment and income limits) is narrow and the 2026 status is uncertain — verify on the IRS / ENERGY STAR resources before assuming it applies. [src5, src6]
• UL or ETL safety certification is non-negotiable. Uncertified imports are a fire, code, and insurance risk. [src1]