Heater choices

3 Best Electric Tankless Water Heaters for Cold Climates in 2026

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Our top 3 picks

1. 1Higher electric outputStiebel Eltron Tempra 36 PlusStiebel Eltron Tempra 36 Plus

   A winter water load that fits the model's table and a home that can support its electrical demand.

   • Electric resistance heating
   • Advanced Flow Control
   • Largest output in the Tempra Plus range

   Keep in mind: The larger heating load may rule it out before the water connections are considered.

   View on AmazonRead our analysis
2. 2Managed winter demandStiebel Eltron Tempra 29 PlusStiebel Eltron Tempra 29 Plus

   A household prepared to keep winter draws within the voltage-specific flow table.

   • Electric heating: 28.8 kW at 240 V
   • Output falls to 21.6 kW at 208 V
   • Advanced Flow Control can reduce water flow

   Keep in mind: Flow control can slow the water when cold-inlet demand exceeds output.

   View on AmazonRead our analysis
3. 3Restricted winter demandRheem RTEX-24Rheem RTEX-24

   A small overlapping water load that the winter sizing table confirms.

   • Electric heating: 24 kW at 240 V
   • Digital temperature control
   • Heating elements replace a gas burner

   Keep in mind: Its maximum advertised flow should not be carried unchanged into a cold-inlet case.

   View on AmazonRead our analysis

The best electric tankless water heater for cold climates must meet the winter flow you need. The home must also have enough power to run it. Cold inlet water raises the heat needed for each gallon. A unit that feels fine in summer may give much less flow in winter. These picks depend on those checks; no unit suits every home.

#1. Stiebel Eltron Tempra 36 Plus: higher electric output

Stiebel Eltron Tempra 36 Plus Stiebel Eltron Tempra 36 Plus

Our verdict:

Higher electric output

A constrained winter demand that fits the manufacturer flow table and a suitable electrical service.

• Electric resistance heating
• Advanced Flow Control
• Largest output in the Tempra Plus range

Keep in mind: The larger heating load may rule it out before the water connections are considered.

View on Amazon

The Tempra 36 Plus is worth checking when a smaller electric unit falls short. It sits at the higher-output end of the Plus range. It includes Advanced Flow Control, which can reduce flow to hold the set temperature. That does not give it an endless source of heat. The winter sizing table still decides whether the load fits.

Start with the coldest supported inlet condition. Compare the desired outlet temperature with that input. Then read the flow the exact model can support. If it is too low for the taps that must run together, you still need a plan. You can reduce overlap, accept less flow or assess another system.

Check the supply before treating this as an easy upgrade. A larger heater can need more electrical work. Its slim case does not show the scale of the load. Ask for the exact model and the full power scope on the quote. If that scope is not feasible, there is little value in refining a water-side plan around this unit.

#2. Stiebel Eltron Tempra 29 Plus: managed winter demand

Stiebel Eltron Tempra 29 Plus Stiebel Eltron Tempra 29 Plus

Our verdict:

Managed winter demand

Households with sufficient electrical capacity that value a steady outlet temperature.

• Electric heating: 28.8 kW at 240 V
• Output falls to 21.6 kW at 208 V
• Advanced Flow Control can reduce water flow

Keep in mind: Flow control can slow the water when cold-inlet demand exceeds output.

View on Amazon

The Tempra 29 Plus suits a lower winter demand when its table confirms enough flow. Its flow control can hold the chosen temperature by reducing volume. That may be a fair trade for a rare overlap. It is a poor way to meet a daily need for two strong showers. The heat still has to be enough for the water load.

Ask what reduced flow would mean at the fixtures you use. A bath can take longer to fill without much trouble. A shower may feel weak before the temperature becomes the main concern. Define the minimum useful flow for each task. That gives you a way to judge the table beyond a simple claim that the unit makes hot water.

The supported supply voltage matters too. Use the output for the voltage at the home, rather than the most favorable column in a data sheet. The Tempra Plus review explains how power and flow control differ. Keep that distinction clear when comparing this model with a larger Plus unit.

#3. Rheem RTEX-24: a restricted-demand option

Rheem RTEX-24 Rheem RTEX-24

Our verdict:

Restricted winter demand

A home with a supported electrical supply and an inlet temperature that suits the required flow.

• Electric heating: 24 kW at 240 V
• Digital temperature control
• Heating elements replace a gas burner

Keep in mind: Its maximum advertised flow should not be carried unchanged into a cold-inlet case.

View on Amazon

The RTEX-24 belongs on this list for a limited load. It is not a blanket choice for a large house in a cold region. Its digital temperature control sets a target; the heating output still limits flow. Check the exact table with the same winter inlet condition used for the other picks. A warm-water maximum is not a fair comparison.

This option can be worth assessing when only one modest draw is essential at a time. Record what the household can keep apart and what must overlap. A proposal based on one shower should say so plainly. It should not quietly rely on people reducing flow every morning unless they have agreed that this is how they want to use the home.

If the winter table leaves too little flow, stop there. A different setting or control display does not add heat. Compare a different size only after checking the power supply. Where electric tankless cannot meet the essential load within a sensible work scope, reconsider the water-heating layout before placing an order. A limited option is useful only when its limit is acceptable.

Factors to consider: best electric tankless water heater for cold climates

Find a winter inlet condition

Use the water entering the heater as the sizing input. The air outside is a different thing. The water source and pipe route can affect what arrives at the home. Use supported local data, then check the actual water when practical. Keep a range if you cannot yet pin down the input.

A summer tap reading tells you about that day. It should not become the winter design point without a reason. Keep summer and winter cases separate so you can see how flow changes with the season. The heater can have the same power input in each case while the amount of useful hot water differs.

The electric sizing calculator lets you compare those inputs. Hold the fixture demand fixed while changing the inlet temperature. Then check the result against the exact model's table. The tool is a heat-duty screen. It does not approve a circuit, select a heater or establish a home's spare power.

Agree which taps must overlap

Count the fixtures that will run together during a normal winter morning. Separate essential overlap from occasional use that can be delayed. A family willing to fill a bath after showers has a different peak from one that needs both at once. Make that choice before sizing, so the result reflects a real use pattern.

At a mixed-water tap, separate total flow from the hot side served by the heater. Keep the same basis when you measure demand and read a sizing table. If the inputs are unclear, ask for them in the quote. A GPM answer can look precise and still be wrong. It must compare like with like.

For a useful home check, write down a normal busy morning. Note when each person showers and which taps are used during that time. Then write down a busy day with guests. Keep the two cases separate. This shows which load is routine and which one you might be willing to manage with a change in timing.

Do the same for a bath. Decide whether a slower fill is fine and how long you are willing to wait. A tap can often be turned down for a fill more easily than for a shower. Use those needs to set the flow you must have. The result is a household choice that can be checked against the heater table.

Keep the water setting fixed while comparing models. Raising it changes the heat needed and can raise scald risk. It is not a sound way to rescue a poor size choice. Bring the full hot-water layout into that decision, including any mixing controls. A product shortlist does not replace the exact unit's safe-use instructions.

Check the power and the location

The heater shares the home's supply with other loads. A panel label does not show all the spare capacity. Have a qualified electrician assess the service and the exact model's needs. The electrical requirements guide explains why an aggregate current estimate is not a wire or breaker schedule.

Cold inlet performance and freeze protection are separate checks. A heater can sit in a protected indoor space and still face a large winter temperature rise. Enough heating output does not make exposed pipes safe from freezing. Follow the manual's location limits and plan for the connected plumbing as well as the unit itself.

Do not infer outdoor approval from a seller's image. Check the exact model documentation. Think about periods without normal heat or power too. An internal protection feature is not a whole-building freeze plan. Keep location approval separate from the question of how much hot water the heater can supply in winter.

How We Picked

These choices use published US manufacturer information and exact catalog identities. We have not carried out cold-weather trials. The comparison weighs supported output against electrical demand, with reduced flow treated as a real cost to the user. A larger model is included as an option to assess, rather than a universal recommendation for cold regions.

Verdict: best electric tankless water heater for cold climates

The best electric tankless water heater for cold climates meets the essential winter load without assuming spare power that has not been confirmed. Check the Tempra 36 Plus for higher output. Assess the 29 Plus and RTEX-24 only where the smaller supported flow is enough. If the water or power check fails, compare another water-heating arrangement.

The general electric comparison covers the control choices in more detail. Keep the winter assumptions with the final quote. They explain what the selected size is meant to do and help you recheck it if new fixtures or a change in use later raises demand.

Sources: Stiebel Eltron Tempra technical documents and Rheem residential tankless information. Published data checked October 16, 2026.

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Quick answers

What is the downside of an electric tankless water heater?

Cold inlet water can leave less flow than the household expects, while a larger heater can require more electrical work. Check both limits together. A higher output label is not useful if the supply cannot support it or the remaining winter flow is too low.

Who makes the most reliable electric tankless water heater?

The published data does not establish a reliability winner. This shortlist compares winter capacity and controls. Read the exact warranty conditions separately, and keep water quality and service access in the plan; a coverage period is not an expected lifespan.