Stiebel Eltron Tempra Plus 36 kW Review: What a 400-Person Facility Buyer Learned
If you're asking whether the Stiebel Eltron Tempra Plus 36 kW is worth the premium, yes, it's worth it—provided your building can supply the electricity and you're willing to put a maintenance reminder on the calendar. I've been buying these units for a 400-person facility since 2020, and I'd choose this model again. But "set it and forget it" it is not.
Stiebel Eltron has a reputation for solid German engineering, and most of it is deserved. The Tempra Plus line is an electric tankless water heater, meaning it heats water on demand instead of keeping a tank hot. The 36 kW model is the biggest single-phase 240V unit in the lineup. We chose it because our incoming groundwater is cold in winter and our staff expects a reliable steady shower temperature.
Before I get into the review, let me be clear about who I am. I'm an office administrator, not a plumber or electrician. I manage purchasing for a multi-location company, which means I've ordered dozens of water heaters, air handlers, and dealt with all the vendor calls that show up with them. This is not a manufacturer's marketing page.
Stiebel Eltron water heater reviews: what's real, what's noise
Most Stiebel Eltron water heater reviews I read before buying focused on build quality and how quietly it operates. Both are true in our experience. The unit feels heavier and better made than a few competing models we ordered. The housing is not creaky plastic. But the most useful review detail wasn't about the unit at all: it was about the electrical panel. The Tempra Plus 36 kW needs a dedicated 150-amp breaker at 240V. If you don't have that capacity, you're paying for a service upgrade before you've paid for the unit itself.
In 2024, during our vendor consolidation project, I almost ordered two more units before checking the panel in one of our smaller locations. The panel was already near capacity. We ended up installing a tank water heater there instead. That's not a knock on Stiebel Eltron; it's a reminder that the water heater is tied to the building's bones.
The Tempra Plus 36 kW's best feature: stable temperature
For a facility, the biggest complaint you get about tankless water heaters is fluctuating temperature when someone turns on another tap. The Tempra Plus handles that better than any electric tankless we've used. It adjusts power in real time based on flow and inlet temperature. The 36 kW gives enough headroom that we don't see a noticeable dip when two or three break-room sinks run at once. Full disclosure: I didn't believe the marketing claim until we tested it during a busy lunch hour, not in an empty building.
The spec sheet on stiebel-eltron-usa.com lists the exact flow rates, and I don't have it in front of me, so I'm not going to quote a number. What I can tell you: it's enough for our usage, and we have never run out of hot water because there is no tank to empty.
According to the U.S. Department of Energy (energy.gov), tankless water heaters can be 24% to 34% more energy-efficient than storage-tank units when you use 41 gallons or less of hot water per day. We are in that range on most days, so the efficiency argument made sense. If your demand is much higher, a tank or hybrid unit is worth considering.
How to flush a hot water heater (the tankless way)
When I search for "how to flush a hot water heater," I get instructions for tank units: turn off the power or gas, attach a hose to the drain valve, and let the sediment run out. A tankless water heater is a different animal. Flushing means descaling the heat exchanger, not draining a tank. If you put off annual maintenance, scale builds up on the heating elements and the unit has to work harder—and eventually it will throw an error code.
I still kick myself for letting the first unit go 18 months without a flush. The heating element scaled up enough that the unit shut down in the middle of winter. The service call plus a replacement element was around $780, which was more than the cost of a professional flush on every unit we owned. The repair guy asked, "When was the last time you descaled this?" I had to admit I didn't know.
Here's the process we follow now, in case it helps. I'm not a plumber, but this is what the manufacturer's manual and our service contractor told us to do:
- Turn off the power at the breaker. This is non-negotiable.
- Close the cold water inlet and hot water outlet shutoff valves.
- Open a hot water tap to relieve pressure.
- Connect a circulating pump to the two service valves on the unit. If your unit has an isolation valve kit, use that.
- Put a descaling solution in a bucket—white vinegar or citric acid works for most electric tankless units.
- Run the pump for 45 to 60 minutes so the solution circulates through the heat exchanger.
- Turn off the pump, close the service valves, remove the hoses, and reopen the main shutoff valves.
- Run hot water for a few minutes to rinse out the vinegar before restoring power.
If you have a standard tank water heater, it's a simpler job: drain, refill, and repeat a few times to remove sediment. But don't confuse the two. For a tankless, it's about scale, not sediment. Note to self: our January reminder is already on the calendar, but I should double-check the current water hardness reading.
Why a heat pump dryer and a crawl space dehumidifier showed up in the same project
The Tempra Plus was not the only equipment change we made. During our 2024 consolidation, we also bought a heat pump dryer and a crawl space dehumidifier from other vendors. This might sound unrelated to a water heater review, but it's not.
A heat pump dryer recycles heat instead of venting it outside, which is great for energy cost. But it also removes moisture from the laundry and has to drain it somewhere. In an adjacent utility room, that water load can affect the space where your water heater lives. The crawl space dehumidifier, in our case, handled persistent humidity that the building's HVAC couldn't fully address. According to EPA (epa.gov), indoor humidity should stay between 30% and 50% to prevent mold growth. We were above that before we added the unit.
Full disclosure: Stiebel Eltron doesn't make either of those in the North American market, as far as I know. I'm bringing them up because they're part of the same energy retrofit conversation. If you're putting together a facility upgrade, don't evaluate the tankless water heater in isolation. Your building's moisture and ventilation profile will affect everything else in that room.
When I would not buy the Tempra Plus 36 kW
If you have a 100-amp panel and a tight budget, the Tempra Plus 36 kW is probably not the right call. The electrical service upgrade alone can cost more than the water heater. In that case, a heat pump water heater or a smaller 120V point-of-use unit might make more sense.
If your water is extremely hard—say, above 10 grains per gallon—you need to be honest about maintenance. The unit won't fail immediately, but scale will cut its lifespan if you skip the flush. A traditional tank water heater is arguably more forgiving in that situation. I'm not going to tell you tankless is universally smarter.
And if you're on a strict deadline, pay extra for delivery certainty. In March 2024, we paid a $400 expediting fee to get a Tempra Plus in time for a tenant move-in. Had I waited for standard shipping, we'd have missed the date and the associated billing. That $400 was cheap compared to the delay. In my opinion, the certainty premium is almost always worth it for deadline-critical projects.
If you're evaluating the Stiebel Eltron Tempra Plus 36 kW, my honest advice is to plan for three things: the electrical service, the annual flush, and the building's humidity story. The unit itself is reliable, the temperature control is excellent, and the German engineering reputation is earned. But no tankless water heater is a zero-maintenance appliance. Budget for the maintenance, and it'll treat you well.