Best Tempra 15 Plus Tankless Water Heater – What You Need to Know!

You step into the shower, turn the knob, and wait. The water runs cold for a full minute. Then it gets warm, then scalding, then cold again. That old tank heater is gasping its last breath. You need something better.

Electric tankless water heaters solve the problem. No tank, no standby losses, no running out of hot water mid-shampoo. Stiebel Eltron has been making these units in Germany for decades. Their Tempra line is the benchmark for reliability and performance. The trick is picking the right power level for your home.

We lined up five Tempra models – from the 12kW entry point to the beastly 36kW unit. Below you’ll find a quick spec table, then a deep look at each model. If you want the short answer: most houses with 200-amp service should go straight to the Tempra 29 Plus. But read on for the details – your electrical panel will thank you.

Here is a side-by-side look at the key specs that separate these models.

Features	Tempra 15 Plus	Tempra 29 Plus	Tempra 12 Plus	Tempra 29 Trend	Tempra 36 Plus
Power (kW)	14.4 kW	28.8 kW	12 kW	28.8 kW	36 kW
Voltage	240V	240 or 208V	240V	240V	240V
Min Service Required	100 A	200 A	100 A	200 A	200 A+
Flow Control	Advanced Flow Control	Standard flow control	Advanced Flow Control	Standard flow control	Standard flow control
Best Use	Small home, 1-2 baths	Whole house, 3-4 baths	Single point or small apartment	Whole house, budget option	Large home, cold climates

Stiebel Eltron Tempra 15 Plus

The Tempra 15 Plus sits in the middle of the Tempra lineup. It draws 14.4 kW at 240 volts and requires only a 100-amp service. That makes it a realistic upgrade for older homes or condos where the electrical panel can’t handle a bigger unit. It will supply one shower plus a kitchen faucet at the same time without a noticeable drop in temperature.

What stands out is the Advanced Flow Control. Stiebel Eltron’s patented system monitors the outgoing water temperature and adjusts the flow rate to keep it steady. If you turn on another tap, the unit reduces flow slightly rather than let the water go cold. The digital display shows the set temperature and a savings monitor that tracks energy use. It’s quiet – you won’t hear it kick on.

The trade-off is flow rate in colder months. If your incoming groundwater is below 50°F, expect a temperature rise of about 45-50°F at 1.5 gallons per minute. That’s enough for a comfortable shower but not for filling a large tub fast. Also, the 14.4 kW version is the only Plus model that requires a single 60-amp breaker – check your panel clearance.

• 14.4 kW, 240V, 60-amp breaker required
• Recommended minimum electrical service: 100 A
• Output temperature range: 68° to 140°F
• Includes 7-year leakage warranty and 3-year parts warranty
• Dimensions: 17.5 x 17.5 x 8.5 inches – fits in tight spaces

Best for: Homeowners with a 100-amp panel who need reliable hot water for one or two low-flow showers.

Stiebel Eltron Tempra 29 Plus

This is the sweet spot for most families. The Tempra 29 Plus delivers 28.8 kW and needs three dedicated 40-amp breakers with 8-gauge copper wire. Your house must have at least 200-amp service. In return, you get enough hot water to run two showers and a dishwasher simultaneously without a hiccup.

The Plus models include two preset temperature memory buttons on the front panel – handy if you prefer a scalding hot kitchen sink and a milder shower. The solid copper heating block is the same design used in commercial units; it resists mineral buildup better than stainless steel coils. The savings monitor is a nice bonus – it tells you how much energy you’ve saved compared to a tank heater in real dollars.

The limitation is the installation cost. Running three 40-amp circuits is not a DIY job for most people. You’ll likely need an electrician to upgrade the panel and pull the wire. That can add $500-$1000 to the total. Also, the 29 Plus is heavy – about 17 pounds – so mount it securely on a wall stud.

• 28.8 kW, 240V, three 40-amp breakers
• Minimum electric service: 200 A
• Two temperature memory presets
• 7-year leakage warranty, 3-year parts warranty
• Made in Germany – consistent build quality

Best for: Families with a 200-amp panel who want endless hot water for multiple simultaneous uses.

Stiebel Eltron Tempra 12 Plus

The Tempra 12 Plus is the entry point for small spaces. At 12 kW and 100-amp service, it’s the smallest Plus model. It works well for a single bathroom apartment, a guesthouse, or an office sink. The Advanced Flow Control is the same as the 15 Plus, so you get the same temperature stability. The digital temperature display and memory buttons are also identical.

What makes it different is the output. With a 12 kW element, you can only expect a temperature rise of about 50°F at 1 gallon per minute. That means if your incoming water is 50°F, you’ll get 100°F out – adequate for a hand wash or a low-flow shower head. It’s also physically smaller than the higher-power models – easier to tuck under a sink.

The catch is that 12 kW is barely enough for a single shower in winter. If you live in a warm climate where groundwater stays above 60°F, it’s fine. But in Minnesota or Maine, you’ll likely be disappointed. Also, the 12 Plus is not much cheaper than the 15 Plus – check the current price difference.

• 12 kW, 240V, single 50-amp breaker
• Recommended minimum service: 100 A
• Output temperature: 68° to 140°F
• Compact dimensions: 14 x 14 x 7 inches
• Same 7-year leakage warranty as larger models

Best for: A small apartment or workshop where hot water demand is low and space is tight.

Stiebel Eltron Tempra 29 Trend

The Tempra 29 Trend is the budget alternative to the 29 Plus. It has the same 28.8 kW heating capacity and requires the same 200-amp service with three 40-amp breakers. But the Trend model drops the Advanced Flow Control, the digital temperature display, and the savings monitor. Instead, you get a simple mechanical flow control and a dial to set the temperature.

That means the Trend is less precise. You won’t get the automatic flow reduction when demand spikes – the water temperature may fluctuate briefly if someone flushes a toilet. But the copper heating block is the same, and the unit still delivers endless hot water. It’s a straightforward, no-frills option for someone who doesn’t mind a slight temperature variation.

The downside is the missing digital display. Setting the temperature requires turning a knob and waiting – not as convenient as the push-button presets on the Plus. Also, the Trend does not have the energy savings monitor, so you won’t see your cost savings in real time. But if you just want hot water and plan to install it in a basement or utility room that you rarely visit, this model saves you money upfront.

• 28.8 kW, 240V, identical electrical requirements to 29 Plus
• Continuous flow – no preset memories
• 7-year leakage warranty, 3-year parts warranty
• Same physical size as 29 Plus
• Usually $100-$150 less than Plus model

Best for: Budget-conscious buyers who have 200-amp service and don’t need digital controls.

Stiebel Eltron Tempra 36 Plus

The Tempra 36 Plus is the largest residential unit Stiebel Eltron makes. At 36 kW, it can handle three simultaneous showers plus a load of laundry. It demands a 200-amp service minimum, but many homes need a 300-amp upgrade to run everything. The unit requires four 40-amp breakers – a substantial electrical commitment.

This particular unit is refurbished – tested, cleaned, and repackaged. Refurbished units from Stiebel Eltron usually perform like new, and they still carry the same 7-year leakage warranty. The upside is a significant price cut. The downside is that refurbished stock is limited, and you might get a generic box without the original retail packaging.

Consider this only if your home has the electrical infrastructure and you truly need the maximum flow rate. For most families, the 29 Plus is sufficient. The 36 Plus makes sense for a large household in a cold climate where groundwater is in the 40s. But the installation complexity and electrical upgrade cost can be steep.

• 36 kW, 240V, four 40-amp breakers
• Refurbished – tested and warranted
• Output temperature: 68° to 140°F
• Same digital display and presets as other Plus models
• Only buy if you have 300-A service or plan to upgrade

Best for: Large families in cold regions with available electrical capacity to spare.

How We Chose These Products

We focused on the Tempra line because Stiebel Eltron dominates the electric tankless market in North America for a reason – reliability and engineering. We selected the five models that cover the most common residential scenarios: from a single point of use (12kW) to whole-house high demand (36kW).

We compared power draw, minimum electrical service requirements, and the presence of Advanced Flow Control. The Plus models have digital controls and savings monitors; the Trend and refurbished options offer lower prices. We gave extra weight to real-world flexibility – a unit that works with a standard 100-amp panel is a much easier upgrade than one requiring 200 amps.

Buying Guide: What Really Matters

Before you buy any tankless water heater, check your electrical panel. Open it up and look for the main breaker amperage. If it says 100, you can run the 12kW or 14.4kW models. If it says 200, you can run the 28.8kW or 36kW models – but you still need to confirm you have spare breaker slots. A qualified electrician can do a load calculation to ensure your panel isn’t maxed out already.

Water quality affects longevity. Hard water causes scale buildup inside the copper heating block. If you have hard water (above 7 grains per gallon), install a water softener upstream to protect the unit. Regular descaling every 6-12 months also helps. Best water softener for tankless water heater can extend your unit’s life significantly.

Flow rate is the other critical factor. Stiebel Eltron rates these units for a specific temperature rise at a given flow. As a rule of thumb, each 10kW of power gives about a 35°F temperature rise at 1.5 gallons per minute. So the 15 Plus (14.4kW) gives roughly a 50°F rise. Know your incoming groundwater temperature – you can measure it with a thermometer at the hose bib. Subtract that from your desired shower temperature (105°F is typical) to find the rise you need, then pick a unit that delivers that rise at the flow rate you want.

Our Top Recommendation

For the majority of homes, the Tempra 29 Plus is the winner. It provides enough hot water for a family of four, has the Advanced Flow Control for steady temperatures, and fits within a standard 200-amp service. If you can’t meet the 200-amp requirement, the Tempra 15 Plus is the best fallback – it will handle a single large shower with decent flow, and it works on a 100-amp panel.

If you’re on a strict budget and have 200-amp service, the Tempra 29 Trend gives you the same heating power without the digital frills. It saves money upfront, and you can always add a separate thermostat later if you need precise control. Avoid the 12kW model unless your hot water needs are minimal – the 15 Plus offers much better value for a small price difference.

Frequently Asked Questions

Can the Tempra 15 Plus run two showers at once?

Probably not in winter. With 14.4 kW, the unit can raise the temperature about 50°F at 1.5 GPM. Two low-flow shower heads at 1.5 GPM each would exceed the flow capacity, and the unit would either shut down or deliver lukewarm water. For two simultaneous showers, you need at least the 29 Plus.

Do I need to flush the Tempra with vinegar regularly?

It depends on your water hardness. If you have soft water (less than 3 grains per gallon), you can go years without descaling. If you have hard water, descale every 12 months using a best tankless water heater descaler to prevent scale buildup. Stiebel Eltron recommends using their own descaling kit, but generic pump systems work too.

What happens if the power goes out? Will I lose hot water?

Electric tankless heaters have no storage, so you lose hot water immediately during a power outage. Unlike a tank heater that holds 40 gallons of pre-heated water, the Tempra only heats water on demand. If you live in an area with frequent outages, consider a hybrid system with a small backup tank or a generator.

Is the Tempra 36 Plus really worth the extra cost over the 29 Plus?

Only if you consistently run three or more hot water fixtures at the same time – think a large family taking showers while the washing machine and dishwasher run in winter. For most homes, the 29 Plus is more than enough. The 36 Plus also requires a bigger electrical upgrade, which adds to the total cost. We’d only recommend it if you’ve already tested your demand and found the 29 Plus lacking.