Running out of hot water halfway through a shower is frustrating. A bulky storage tank also takes up valuable space and repeatedly reheats water you may not need. The best electric tankless water heaters solve both problems by heating water only when a faucet or appliance calls for it. This guide covers compact point-of-use heaters, versatile mid-sized units, and powerful whole-house models. More importantly, it explains the electrical demands and realistic flow rates you should consider before buying.

Our Top Picks

Product	Best For	Key Feature	Rating
Stiebel Eltron Tempra 24 Plus	Best overall	Advanced Flow Control	★★★★⯪
Rheem RTEX-18	Small homes	Self-modulating 18kW output	★★★★⯪
EcoSmart ECO 27	Best value	Strong whole-house performance	★★★★⯪
Rheem RTEX-13	One shower or bathroom	Compact 13kW design	★★★★⯪
EcoSmart ECO 11	Warm climates	Low-flow versatility	★★★★⯪
Stiebel Eltron Tempra 36 Plus	Large households	Powerful 36kW output	★★★★⯪
Rheem RTEX-24	Multiple fixtures	Adjustable 24kW heating	★★★★⯪
EcoSmart ECO 18	Apartments	Balanced size and output	★★★★⯪
Eemax EEM24027	Whole-house value	Self-modulating technology	★★★★⯪
WINTEMP 18kW	Remote Temperature controls	LED display, Wi-Fi controls	★★★★⯪

Top 10 Electric Tankless Water Heaters

1. Stiebel Eltron Tempra 24 Plus

The Tempra 24 Plus is my top choice for homes that need reliable performance without jumping to an oversized 36kW unit. Its standout feature is Advanced Flow Control, which slightly limits the water flow when demand exceeds capacity rather than letting the temperature suddenly drop.

It works particularly well in small to medium homes with moderate groundwater temperatures. However, it requires two dedicated 50-amp circuits, so your electrical panel must have enough available capacity.

Key features: 24kW output, Advanced Flow Control, digital temperature control, copper heating system
Best for: Small and medium households wanting stable water temperature
Pros: Excellent temperature consistency; quiet operation; strong build quality
Cons: Premium price; demanding electrical requirements
Why I recommend it: It handles changing demand more gracefully than many cheaper heaters, making showers noticeably more comfortable.

2. Rheem RTEX-18

The Rheem RTEX-18 offers a practical middle ground between point-of-use and full whole-house heaters. Its 18kW output can support a shower and a low-flow faucet in favorable conditions, although colder incoming water will reduce that capacity.

A front-mounted knob and digital display make one-degree temperature adjustments simple. The copper immersion heating elements are also serviceable, which may make long-term maintenance easier.

Key features: 18kW output, self-modulating power, digital display, copper heating elements
Best for: Apartments, cabins, and small homes
Pros: Straightforward controls; compact body; reputable manufacturer
Cons: May struggle with simultaneous showers; professional wiring required
Why I recommend it: It delivers useful household capacity without the extreme electrical load of larger models.

3. EcoSmart ECO 27

The ECO 27 remains one of the most popular whole-house electric models because it combines a reasonable purchase price with substantial heating power. EcoSmart’s self-modulating system adjusts energy consumption according to flow and the required temperature rise.

In warm regions, it may handle several fixtures at once. Homes in colder climates should expect lower flow or consider a larger unit.

Key features: 27kW output, self-modulating technology, one-degree adjustments, compact wall mounting
Best for: Budget-conscious whole-house installations
Pros: Strong value; widely available replacement parts; easy temperature adjustment
Cons: Performance depends heavily on incoming water temperature; requires three 40-amp breakers
Why I recommend it: It offers one of the most attractive power-to-price ratios in this roundup.

4. Rheem RTEX-13

The RTEX-13 is designed for lighter demand. It can serve a bathroom, utility area, or single shower where the incoming water is not extremely cold.

Its modest size makes it easier to install near the fixture, reducing the amount of cooled water sitting inside long plumbing lines. It uses one 60-amp double-pole breaker, but that still calls for professional electrical work.

Key features: 13kW output, digital thermostat, self-modulating control, included adapters
Best for: A single bathroom, shower, or other point-of-use application
Pros: Compact; precise controls; serviceable copper elements
Cons: Not intended for several high-flow fixtures; limited cold-climate capacity
Why I recommend it: It is a sensible choice when you need to heat one zone rather than the entire home.

5. EcoSmart ECO 11

The ECO 11 is a compact 13kW heater suited to a sink, low-flow shower, office breakroom, or small apartment in a warm climate. Its activation flow is low enough for many point-of-use installations.

Despite the “ECO 11” name, the unit produces up to 13kW at 240 volts. Buyers should not mistake it for a conventional plug-in appliance—it requires a dedicated 60-amp circuit.

Key features: Up to 13kW, self-modulating operation, digital control, compact housing
Best for: Warm climates and low-flow applications
Pros: Affordable; small footprint; widely reviewed
Cons: Limited winter performance; unsuitable for a busy whole home
Why I recommend it: It covers modest hot-water needs without paying for capacity you cannot use.

6. Stiebel Eltron Tempra 36 Plus

Large families with sufficient electrical service should consider the Tempra 36 Plus. Its 36kW output provides more headroom for concurrent showers and appliances, especially in areas with moderately cold inlet water.

That performance comes with serious installation demands. It typically needs three dedicated 50-amp circuits, making an electrical-service assessment essential before purchase.

Key features: 36kW output, Advanced Flow Control, digital thermostat, solid copper heating system
Best for: Larger households with high hot-water demand
Pros: Strong capacity; stable outlet temperature; refined controls
Cons: Expensive; very high electrical demand
Why I recommend it: It is one of the more capable all-electric options for households that regularly use several fixtures.

7. Rheem RTEX-24

The RTEX-24 suits homeowners who like Rheem’s accessible controls but need more capacity than the RTEX-18 provides. It continuously adjusts power according to flow, helping reduce unnecessary energy use during lighter demand.

It is a good candidate for a small whole-house system, though real output changes with the required temperature rise. Have an electrician confirm that the panel can support its three 40-amp circuits.

Key features: 24kW output, self-modulation, LED display, durable heating chambers
Best for: Small homes using multiple fixtures
Pros: Simple interface; solid mid-range capacity; compact installation
Cons: Significant panel requirements; output declines in cold regions
Why I recommend it: It provides a useful step up in capacity without moving into the largest price bracket.

8. EcoSmart ECO 18

The ECO 18 fits between EcoSmart’s smaller point-of-use heaters and its high-output whole-house models. For an apartment or one-bathroom home, it may provide a better balance than paying for an ECO 27.

The unit monitors inlet temperature and flow before applying the required power. Like every tankless heater, however, it cannot exceed its physical heating capacity during heavy demand.

Key features: 18kW output, self-modulation, digital thermostat, replaceable components
Best for: Apartments and compact one-bathroom homes
Pros: Good size-to-output balance; simple controls; competitive price
Cons: Not suitable for two busy bathrooms; requires two 40-amp circuits
Why I recommend it: It delivers more flexibility than a basic point-of-use heater without imposing the load of a 27kW model.

9. Eemax EEM24027

The Eemax EEM24027 is a 27kW alternative for homeowners comparing whole-house electric systems. It uses self-modulating technology to direct energy to the heating elements according to current demand.

Its slim wall-mounted design frees up floor space, but installation expenses may offset some of the savings over a premium heater. Hard-water households should also plan for regular descaling.

Key features: 27kW output, self-modulation, digital temperature control, compact profile
Best for: Value-focused whole-house installations
Pros: Strong output; uncluttered controls; space-saving body
Cons: Requires three circuits; fewer service options in some areas
Why I recommend it: It gives shoppers another capable 27kW option beyond the most commonly promoted brands.

10. WINTEMP 18kW Electric Tankless Water Heater

WINTEMP’s 18kW model pairs self-modulating heating with an LED temperature display and Wi-Fi controls. The listing advertises up to 4.3 GPM, though actual hot-water flow depends on the incoming water temperature. It is a practical option for a shower and a smaller tap when local conditions allow.

Check the electrical requirements before ordering: WINTEMP recommends 150-amp household service for this 240V unit. The compact wall-mounted design saves space, but installation may be a substantial expense if your electrical setup needs an upgrade.

Key features: 18kW output, up to 4.3 GPM advertised flow, LED display, Wi-Fi controls, self-modulating heating
Best for: Buyers who want remote temperature control and have suitable electrical capacity
Pros: Wi-Fi controls; compact design; automatic power adjustment
Cons: Demanding electrical requirements; flow falls as the required temperature rise increases
Why we recommend it: It combines useful controls with enough heating power for modest simultaneous hot-water needs, provided the home and climate suit an 18kW unit.

How to Choose an Electric Tankless Water Heater

Do not choose a heater by its advertised maximum GPM alone. Manufacturers calculate maximum flow under specific temperature conditions, and your results may differ substantially in winter.

Start with these four factors:

• Required flow: Add the flow rates of fixtures that may run together. A modern shower commonly uses roughly 1.5–2.5 GPM.
• Temperature rise: Subtract the incoming water temperature from your desired outlet temperature. Colder inlet water requires more power.
• Electrical capacity: Large units may need two or three dedicated 240-volt circuits plus substantial panel capacity.
• Activation rate: A heater with a high minimum flow may not activate when a faucet is only slightly open.

Professional installation is strongly recommended. Improper wiring, undersized conductors, or incorrect breakers can create a serious fire hazard and may void the warranty.

If the heater is part of a broader kitchen renovation, plan its location alongside cabinetry, seating, and plumbing. These leather banquette seating ideas for kitchens can help you think through the surrounding layout before walls and utility lines are finalized.

Final Thoughts

The Stiebel Eltron Tempra 24 Plus is the best all-around choice for its dependable temperature control and strong build quality. The EcoSmart ECO 27 offers better value for whole-house use, while the Rheem RTEX-13 and EcoSmart ECO 11 make more sense for a single bathroom or fixture. Whichever electric tankless water heater you choose, calculate your temperature rise and confirm the available electrical service first. Proper sizing matters far more than buying the model with the largest advertised flow rate.

Frequently Asked Questions

Are electric tankless water heaters worth it?

They can be worthwhile when you want continuous hot water, compact installation, and no standby tank losses. The main drawback is the cost of electrical upgrades if your existing panel cannot support the required amperage.

What size electric tankless water heater do I need?

A sink may need only 3–8kW, while a shower often calls for approximately 13–18kW. Small whole-house installations commonly use 18–27kW, while larger households may need 29–36kW. Climate and simultaneous flow ultimately determine the right size.

Can an electric tankless water heater supply an entire house?

Yes, but only when it is correctly sized for the home’s incoming water temperature and peak flow. In cold climates, even a large unit may require users to limit simultaneous showers or appliance use.

Do electric tankless water heaters need maintenance?

Yes. Mineral deposits can reduce flow and heating efficiency, especially in hard-water areas. Periodic flushing or descaling according to the manufacturer’s instructions helps preserve performance.

Can I install an electric tankless water heater myself?

Most whole-house models should be installed by licensed electrical and plumbing professionals. They draw substantial current, require dedicated breakers and heavy-gauge wiring, and must comply with local codes. Professional installation may also be necessary to protect the warranty.