The best electric tankless water heater for whole-home use in 2026 is the EcoSmart ECO 36 — 36 kW of heating power, a 0.99 UEF, and up to 6.1 GPM at 35°F rise, for $550–$700. For point-of-use, the EcoSmart ECO 11 delivers 2.2 GPM on a single 60A circuit for under $300.
Electric tankless heaters convert nearly 100% of input energy to hot water (0.96–0.99 UEF), require no venting, produce zero combustion emissions, and cost 40–70% less to install than gas. The trade-off is lower flow capacity — the largest residential electric unit tops out at 36 kW (122,800 BTU/h equivalent), versus 199,900 BTU/h for gas.
Understanding Electric Tankless Specs
Before comparing models, you need to understand three electrical specifications that determine whether an electric tankless heater will work in your home:
Power Rating (kW)
This is the heating capacity. More kW = more hot water. Residential units range from 3.5 kW (a single-sink unit) to 36 kW (whole-home in warm climates). The relationship between kW, flow rate, and temperature rise follows a simple formula:
GPM = kW × 5.86 ÷ Temperature Rise
At 36 kW with a 50°F rise: 36 × 5.86 ÷ 50 = 4.2 GPM (two fixtures comfortably). At 36 kW with a 77°F rise: 36 × 5.86 ÷ 77 = 2.7 GPM (one shower, maybe).
Amperage Draw
This is what determines whether your electrical panel can support the unit. Formula:
Amps = kW × 1,000 ÷ Voltage
A 36 kW unit at 240V draws: 36,000 ÷ 240 = 150 amps. That's 75% of a 200A panel's total capacity. Most 36 kW units split this across multiple circuits — typically four 40A breakers.
Circuit Configuration
Electric tankless units use multiple parallel heating elements, each on its own circuit. Here's how the most common configurations break down:
Panel reality check: A 200A panel has 200A total capacity, shared among ALL circuits — HVAC, range, dryer, lighting, etc. A typical home's existing load is 80–120A. Adding a 27 kW tankless (113A) to a home using 100A leaves only 87A of margin — which is tight. Have an electrician perform a load calculation (NEC Article 220) before committing to a whole-home electric tankless.
Top 10 Electric Tankless Water Heaters for 2026
Whole-Home Models (18–36 kW)
Point-of-Use Models (3.5–13 kW)
Detailed Reviews
#1: EcoSmart ECO 36 — Best Overall Electric
The ECO 36 has dominated the electric tankless category for years, and for good reason. At 36 kW with a 0.99 UEF, it extracts maximum heat from every kilowatt. The self-modulating technology adjusts power draw in real time — heating a single sink uses only 5–8 kW, not the full 36.
The digital temperature control adjusts in 1°F increments from 80–140°F. The compact enclosure (17" × 17" × 3.75") fits in a closet, under a sink, or on a utility room wall. The patented copper and stainless steel components resist corrosion.
EcoSmart's lifetime warranty on the heat exchanger (for the original owner) is the longest in the electric category. Replacement heating elements are $30–$50 each and take 15 minutes to swap.
Key limitation: At 36 kW, you need 150A of available panel capacity. If your panel is maxed, budget $1,500–$3,000 for a panel upgrade.
Ideal climate range: Groundwater above 57°F for whole-home 2-fixture use. Below 57°F, it becomes a 1-fixture unit.
Real-world example: A couple in Tampa, FL (groundwater 72°F, 48°F rise needed) installed the ECO 36 in their 1,800 sq ft home. It delivers 4.4 GPM at 48°F rise — running two showers simultaneously with no temperature drop. Existing 200A panel had 80A of headroom. Installation cost: $1,400 total. Monthly electric increase: $18. Monthly savings vs old 50-gallon tank: $24. Net savings: $6/month, plus they reclaimed closet space.
#2: Stiebel Eltron Tempra 36 Plus — Best Premium Electric
The Tempra 36 Plus shares the ECO 36's 36 kW / 0.99 UEF specs but adds one killer feature: Advanced Flow Control (AFC). When demand exceeds the unit's heating capacity, AFC automatically reduces flow rate to maintain temperature, rather than delivering lukewarm water. You get warm water at lower pressure instead of cold water at full pressure.
The temperature display is accurate to 1°F, and the control knob provides smooth analog adjustment. Copper heating chambers and brass fittings signal the German engineering pedigree. The 7-year parts warranty is shorter than EcoSmart's lifetime but backed by Stiebel Eltron's excellent customer support.
Best for: Homeowners who want temperature consistency above all else, even if it means temporarily reduced flow.
Real-world example: A family of 3 in Sacramento, CA (groundwater 60°F, 60°F rise) relies on the Tempra 36 for their 3-bathroom home. During peak demand (two showers + dishwasher), AFC briefly reduces shower flow from 2.0 to 1.6 GPM — barely noticeable. Without AFC, the temperature would have dropped 5–8°F.
#3: Rheem RTEX-36 — Best Value Whole-Home
Rheem's RTEX-36 matches the ECO 36 and Tempra 36 on specs but costs $50–$200 less. The digital temperature display, self-modulating technology, and 36 kW heating capacity are all present. The main trade-off is warranty: Rheem's 5-year limited warranty on the heat exchanger is significantly shorter than EcoSmart's lifetime coverage.
Available at Home Depot and through every major plumbing supply house, parts are never hard to find. The unit shares the same 17" × 17" × 3.75" footprint as competitors.
Best for: Budget-conscious whole-home electric installs where warranty length isn't the top priority.
#4: EcoSmart ECO 27 — Best Mid-Range
At 27 kW and $400–$550, the ECO 27 hits a sweet spot for smaller homes and warm climates. It draws 113A at 240V across three 40A circuits — a more manageable panel load than the 36 kW units.
At a 35°F rise, it delivers 4.6 GPM (two full showers). At a 50°F rise, it delivers 3.2 GPM (one shower plus a faucet). This is the right unit when you need more than point-of-use but don't need 36 kW of whole-home power.
Best for: 1–2 bathroom homes in warm climates, homes with 150A panels, or as a dedicated unit for a large master bathroom.
#5: Stiebel Eltron Tempra 29 Plus — Best Flow Control Mid-Range
The Tempra 29 Plus (29 kW) includes Stiebel Eltron's Advanced Flow Control at a lower power level. Delivers 4.9 GPM at 35°F rise, and the AFC feature ensures consistent temperature even when two fixtures run simultaneously.
At $600–$800, it's the premium option in the mid-range category. The three 50A circuits need #6 AWG wire — slightly more expensive than the #8 AWG used by 40A circuit configurations.
#6: Rheem RTEX-24 — Best Budget Whole-Home
At 24 kW and $400–$550, the RTEX-24 is the cheapest path to whole-home electric tankless. It delivers 4.1 GPM at 35°F rise — enough for a single shower plus a faucet in moderate climates. Three 40A circuits at 240V draw 100A total.
This unit works best in warm climates (Southeast, Southwest, coastal) where groundwater temperatures above 65°F keep the required temperature rise manageable.
#7: EcoSmart ECO 11 — Best Point-of-Use
The ECO 11 punches above its weight at 13 kW. A single 60A circuit delivers 2.2 GPM at 35°F rise — enough for a full shower in warm climates or a bathroom sink and handwashing in cold climates.
At $200–$300 and 11.5" × 8" × 3.75", it's the go-to for guest bathrooms, home offices, pool houses, garages, and any space where running hot water pipes from the main heater is impractical. Installation takes 2–3 hours for a licensed electrician.
#8–#10: Compact Point-of-Use Models
Stiebel Eltron Tempra 12 Plus ($350–$450): Premium build quality for single-fixture use. AFC technology prevents cold surprises. 12 kW on a single 50A circuit. Best for kitchens and bathrooms where consistent temperature matters.
Rheem RTEX-08 ($180–$250): Ultra-compact 8 kW unit on a single 40A circuit. Delivers 1.4 GPM at 35°F rise — perfect for a handwashing sink or utility sink. The cheapest name-brand electric tankless.
Bosch Tronic 3000T ($200–$280): Bosch's reliable point-of-use model at 7.2 kW. Compact design mounts in tight spaces. Best for commercial handwashing stations and restroom sinks.
Point-of-use strategy: Instead of one large whole-home unit, consider multiple point-of-use units at each fixture group. Two ECO 11 units ($600 total) on separate circuits can serve two bathrooms independently, with simpler wiring and no central failure point.
Climate-Based Sizing Guide
Electric tankless performance is entirely climate-dependent. Here's a realistic sizing chart based on groundwater temperature:
Cold-climate reality: In northern states with groundwater below 50°F, electric tankless can only serve 1 fixture at a time — even with a 36 kW unit. For whole-home hot water in cold climates, you need gas tankless, a heat pump water heater, or multiple electric tankless units in parallel.
Electrical Panel Assessment
Before buying an electric tankless, answer these three questions:
1. What's Your Panel Rating?
Check the main breaker at the top of your electrical panel. Common ratings: 100A, 125A, 150A, 200A, or 400A. A whole-home electric tankless (27–36 kW) practically requires a 200A panel.
2. What's Your Available Capacity?
Your existing loads (HVAC, range, dryer, EV charger, etc.) consume a portion of your panel's capacity. An electrician can perform a load calculation per NEC Article 220 to determine available amperage. If your total load exceeds 80% of panel capacity, you need an upgrade.
3. Do You Have Space for New Breakers?
A 36 kW unit needs four double-pole 40A breaker slots — that's 8 slots total. Many older panels are full or have only 2–4 open slots. A sub-panel ($300–$600) or main panel upgrade ($1,500–$3,000) may be needed.
Installation Cost Breakdown
Real-World Examples
Example 1: Southern California Condo
Setup: 1,200 sq ft, 2 bathrooms, couple. Groundwater: 62°F. 200A panel with 90A available.
Unit: EcoSmart ECO 27 (27 kW, 113A draw across 3 circuits). Delivers 3.9 GPM at 58°F rise — two showers simultaneously, just barely.
Install cost: $1,650 (unit $480, electrician $700, materials $350, permit $120).
Operating cost: ~$22/month, down from $35/month with old 40-gallon tank. Annual savings: $156.
Example 2: Florida Vacation Home
Setup: 1,600 sq ft beach house, 2 bathrooms, used seasonally. Groundwater: 74°F. 200A panel.
Unit: EcoSmart ECO 24 (24 kW). Delivers 4.5 GPM at 46°F rise — more than enough.
Install cost: $1,200 (unit $430, electrician $500, materials $200, permit $70).
Result: Zero standby losses when the house sits empty — the old tank wasted $15/month keeping water hot 24/7 in an empty house. Annual savings: $240+ including eliminated standby waste.
Example 3: Point-of-Use for Home Office
Setup: Home office with a half-bath 40 feet from the main water heater. Hot water took 30+ seconds to arrive.
Unit: Rheem RTEX-08 (8 kW) installed under the sink.
Install cost: $520 (unit $200, electrician $250, materials $70). Single 40A circuit.
Result: Instant hot water at the sink. The 1.4 GPM capacity is more than enough for handwashing. No more running the faucet for 30 seconds waiting for hot water.
Example 4: Multi-Unit Strategy in North Carolina
Setup: 2,400 sq ft home, 3 bathrooms. Groundwater: 55°F. 200A panel fully utilized (HVAC, EV charger).
Solution: Instead of one 36 kW unit (impossible — no panel capacity), installed three EcoSmart ECO 11 units (13 kW each, 39 kW total) — one per bathroom. Each runs on its own 60A circuit. Staggered demand means the actual simultaneous draw rarely exceeds 26 kW.
Install cost: $2,800 total. No panel upgrade needed because loads are distributed.
Key Takeaways
- Best overall electric: EcoSmart ECO 36 (36 kW, 0.99 UEF, $550–$700, lifetime warranty)
- Best premium: Stiebel Eltron Tempra 36 Plus (Advanced Flow Control prevents cold surprises)
- Best point-of-use: EcoSmart ECO 11 (13 kW, single 60A circuit, under $300)
- Electric only works for whole-home in warm climates (groundwater 57°F+)
- Check your panel first — a 36 kW unit needs 150A of available capacity
- Consider multiple point-of-use units as an alternative to one large whole-home unit
- 0.99 UEF across all models — electric is nearly 100% efficient, so the differentiator is capacity, not efficiency
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