Heater choices

Stiebel Eltron Tempra Plus Tankless Water Heater Review in 2026

As an Amazon Associate, this website earns from qualifying purchases.

Our pick

1. 1Flow controlStiebel Eltron Tempra 29 PlusStiebel Eltron Tempra 29 Plus

   A home with enough electrical capacity that values 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: Holding temperature can mean a slower flow when demand exceeds output.

   View on AmazonRead our analysis

The Stiebel Eltron Tempra Plus tankless water heater uses electric heat and active flow control. This review covers the Tempra 29 Plus. Choose it when the home's power supply and winter hot-water demand fit its data sheet. Its small case can save space, but the load on the home's power supply is large.

Choose the Plus for steady water temperature if you accept that flow can fall under heavy demand. Confirm the winter flow and the full electrical scope before buying. The small case saves wall space, while the supply needs can still make this a large project.

Stiebel Eltron Tempra 29 Plus Stiebel Eltron Tempra 29 Plus

Our verdict:

Flow control

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: Holding temperature can mean a slower flow when demand exceeds output.

View on Amazon

Stiebel Eltron Tempra Plus tankless water heater: the flow trade-off

The main reason to choose Plus is Advanced Flow Control. When the water demand is too high, it can reduce the flow to hold the set temperature. You may get a slower shower when another tap opens. Decide whether that is a result your household can accept. A control feature cannot add heat beyond the unit's output.

This is a useful choice where the normal draw fits the heater and high demand is rare. It is a poor way to cover a daily need that is too large. If two showers run together each morning, size for that use. Do not count on the controls to hide a gap between the water you want and the heat the unit can supply.

The product name also matters. Plus and Trend are different ranges. Plus adds active flow control; a similar power figure on a Trend model does not mean it has the same feature. Check the full model name on the quote and on the order. A photo of the case is not enough to confirm the controls inside it.

Output at your supply voltage

The Tempra 29 Plus is listed at 28.8 kW on 240 V and 21.6 kW on 208 V. Those figures describe different supplies. Use the data for the voltage at the home. A plan based on the higher output will overstate the heat available if the site has the lower voltage.

Power is only half the sizing check. The other half is the water load. Temperature rise is the gap between the cold water entering the heater and the hot water leaving it. Cold winter water needs more heat for the same flow. A flow figure based on warm inlet water cannot tell you how a winter shower will feel.

Start with the water that really runs at the same time. A bath filled alone is a different load from a shower plus a kitchen tap. Measure flow where possible. Keep the total mixed flow at a shower separate from its hot-water share. Use the same basis when you read the maker's table or compare two units.

Our electric sizing calculator helps estimate the heat duty from flow and temperature rise. Use it to screen the load, then check the exact model's table. It does not choose wire sizes or approve a service. An installer still needs the unit's manual and the home's actual supply details.

Power supply and installation

The unit needs a hard-wired supply. This is work for a qualified electrician and plumber. Do not infer spare capacity from empty spaces in a panel. Other large loads still count. A home can have room for more breakers while lacking the capacity to run the new heater with its other equipment.

Ask for the electrical scope before you order. The quote should name the voltage and the heater model. It should state what supply changes are needed and what remains unknown. A price for mounting a small wall unit does not settle the cost of getting enough power to it. Keep those parts of the job separate.

Do not turn aggregate current into a circuit design. Dividing power by voltage can show the scale of the load, but it does not give a complete wire or breaker schedule. The manual sets model-specific needs. Local code and the way the wiring is installed also matter. Leave that design to the trade doing the work.

The electrical requirements guide explains this gap. If the required changes are large, compare other ways to heat water. Wall space saved by tankless does not prove it is the least costly choice. Compare the complete project, including any changes to the service, rather than the heater alone.

Daily use and water quality

The Plus also offers two temperature memory presets. They provide a way to return to chosen settings without treating each change as a new sizing decision. A saved target is still only a target. It does not add heating output, store a reserve of hot water or remove the flow limit at the current inlet temperature.

Discuss the intended settings as part of the whole hot-water system. The manual and any mixing controls still govern safe use. Do not assume that a convenient preset is a separate scald-protection device. The practical benefit is control convenience; the household still needs an appropriate setting and enough supported flow for the task.

Keep that distinction clear when comparing Plus with a simpler control. If users never change the target, memory may offer less day-to-day value. If they do change it, returning to a known setting can be useful. Neither use case should outweigh a mismatch in winter output or an electrical supply that cannot support the chosen size.

The lack of a combustion flue can help where a gas vent route is hard to arrange. It does not remove the need for plumbing access or a suitable mounting place. Leave space to reach the cover and the connections. A unit hidden behind shelves can be hard to service even if it fits neatly on the wall.

Check the water against the maker's limits. Hard water calls for a plan based on measured conditions. Do not assume that any filter removes hardness. A treatment choice should address the water actually supplied to the house. Follow the model's care instructions, and ask who will carry out routine service before the unit is installed.

Keep the manual and proof of the exact model with the home's records. Later service should use those documents. Similar-looking heaters can have different needs. A generic gas-heater flushing guide is not a substitute for the electrical model's procedure. Follow the safe isolation steps in the correct manual and use a qualified trade when needed.

Warranty coverage also needs a close read. Parts, labor and leak coverage can have different terms. A period named in a sales headline is not a promise that every repair is covered for that long. Read the conditions and keep the purchase and installation records. A warranty length is not an expected service life.

How We Picked

This is a published-data review. We checked the exact catalog identity against Stiebel Eltron's US product page and technical documents. We have not installed or tested the heater. The verdict weighs its flow-control behavior against its supply needs. Customer stars and claims of trouble-free use do not form the basis of our recommendation.

The important comparison is what happens at the limit. Power modulation changes the heat used for a draw. Active flow control can change the water passing through the unit. Those are separate jobs.

A temperature setting is a target, not proof of enough heat for every tap. We treat reduced flow as a real trade-off. Ask how the home would cope if the flow fell during the busiest part of the day. If the answer is that people would keep opening taps to restore volume, this may be the wrong control choice.

The review also keeps the family and the model separate. A claim about the Plus controls does not mean every Plus size meets the same demand. The 29 Plus is one option in the range. Choose its size from winter conditions and supported flow, then check that the home can supply it. Brand preference comes after those checks.

Verdict: Stiebel Eltron Tempra Plus tankless water heater

The Stiebel Eltron Tempra Plus tankless water heater suits a known water load and a home with enough electrical capacity. The 29 Plus can hold the chosen temperature by reducing flow when needed. Buy it only if the supported winter flow still works for your household. If a slower shower is unacceptable, size for the full overlap or compare a different system.

For other electric choices, see the electric heater comparison. It compares Plus with a Trend model and the Rheem RTEX-24. Keep the inlet water and voltage assumptions fixed across all three. A fair comparison asks each heater to meet the same load, rather than picking the largest headline flow.

Before placing the order, bring the quote back to the sizing inputs. Confirm the supply voltage and the winter inlet condition. Check the flow when taps overlap. Ask which parts of the work are included and who will service the unit. Those answers turn a model choice into a workable plan for the home.

Keep a copy of those inputs with the final quote. A later change of shower head or a new high-flow fixture can change the load. The heater name may stay the same while the demand grows. Recheck the flow table when the use changes, rather than assuming that the original sizing choice still covers the house. That record also helps the next owner understand why this size was chosen.

Source: Stiebel Eltron Tempra Plus product page and technical documents. Documents checked October 16, 2026. Use the current exact-model manual for installation and care.

Related guides

• Noritz tankless water heater

Quick answers

How to get more hot water from a tankless water heater?

First check whether winter temperature rise or overlapping fixtures are the limiting load. Staying within the supported flow can keep the outlet at its target. The Plus flow control may reduce volume under excess demand; it does not add heating power.

How are tankless hot water heaters rated?

Compare heating output at the actual voltage and flow at the required rise. The Tempra 29 Plus has different output on its supported supply voltages. A temperature setting alone does not show how much water can be heated at once.

Who makes Stiebel Eltron?

Stiebel Eltron is the manufacturer. This review uses its US product and technical documents for the Tempra Plus range and the exact catalog identity of the 29 Plus. It is a published-data assessment, without hands-on testing.