How many amps does the Stiebel Eltron Tempra 24 draw?

The Tempra 24 is rated 24 kW at 240 V, which is 100 A of continuous current using P = I x V, identical to any other 24 kW electric tankless unit. NEC 422.13's continuous-load rule adds a 125 percent factor for the circuit and breaker, bringing the design load to 125 A. Proportional modulation does not change this figure.

What does proportional modulation mean on the Tempra 24?

Stiebel Eltron describes the Tempra line as adjusting heating element output continuously to match the flow the unit senses, rather than switching fixed-wattage elements on and off in stages. The intent is a steadier outlet temperature as demand changes mid-use, for example when a second fixture opens. It does not change the unit's 24 kW nameplate rating or its electrical draw.

Does the Tempra 24 draw less power than a fixed-element 24 kW heater?

No. Current draw is set by the nameplate kilowatt and voltage rating, not by the control method. A Tempra 24 and a fixed-element 24 kW competitor both draw 100 A continuously and both carry a 125 A NEC design load. Modulation affects how smoothly output changes, not how much power the unit is rated to use.

How much flow does the Tempra 24 deliver at a 55 degree rise?

Calculated from its published 24 kW rating, the Tempra 24 works out to about 2.92 GPM at a 55°F rise. This is the same calculated figure as any other 24 kW, 240 V electric tankless unit, since flow output is a function of kilowatts and rise rather than the control technology used to deliver it.

Can the Tempra 24 run on a 100 amp panel?

Not on its own with any margin. A 125 A design load leaves essentially nothing for the rest of a 100 A panel, so this unit needs a larger service, most commonly 200 A, with a licensed electrician's load calculation confirming spare capacity before installation.

Does the Tempra 24 help with the cold water sandwich effect?

Stiebel Eltron's proportional modulation is built to reduce the temperature swing that happens when demand changes mid-use, which is one contributor to the cold water sandwich effect on any tankless unit. It addresses output stability, not the separate delay caused by hot water already in the pipe cooling before a fresh draw reaches the tap.

Tankless Electric

Stiebel Eltron Tempra 24 Review: The Modulation, Not the Kilowatts

Researched from the DOE test procedures, NFPA 54 and NEC code tables, and manufacturer specifications. Updated 2026-09-17.

Quick answer

The Stiebel Eltron Tempra 24 is rated 24 kW at 240 V, the same nameplate as any 24 kW unit, which draws 100 A continuously and needs 125 A of design-load capacity under NEC 422.13. It suits a household on a confirmed service that also wants steadier outlet temperature during fixture cycling through proportional modulation; it does not suit anyone expecting a lower amp draw for that feature, because the electrical math is identical to a fixed-element 24 kW competitor.

The Tempra 24 draws exactly what its 24 kW, 240 V nameplate says it draws, and that math does not care which brand made the box. A 24 kW electric tankless heater is 100 A of continuous current and 125 A of NEC design load whether it is a Rheem, an EcoSmart, or a Stiebel Eltron.

What differs between brands at the same kilowatt rating is how the unit modulates. Stiebel Eltron describes the Tempra line as adjusting element output to match the flow it senses, rather than switching fixed-wattage heating elements on and off in blocks the way some competitors do. That is the actual reason to consider this specific unit over another 24 kW box, not the electrical service question, which is identical either way.

What do the Tempra 24's specifications actually say?

Stiebel Eltron publishes 24 kW and 240 V for this model. The amperage and design load below follow from those two figures with the same arithmetic used for every 24 kW unit in this category.

Tempra 24 electrical draw, calculated from the published nameplate rating
Specification	Value
Nameplate rating (published)	24 kW at 240 V
Current draw (I = P / V)	100 A
NEC 422.13 continuous-load factor	125 percent of nameplate draw
Design load for circuit and breaker sizing	125 A
Number of circuits	Specified in Stiebel Eltron's installation manual, not published in this listing. Units above roughly 14 kW are typically split across multiple circuits.

Published standard Source: Nameplate kW and V from the product listing; amperage and design load calculated with P = I x V and NEC 422.13's 125 percent continuous-load rule.. This table is identical in method and result to any other 24 kW, 240 V electric tankless unit; the modulation technology described below does not change the panel math.

How much flow does the Tempra 24 deliver, and what does temperature rise cost you?

Flow scales with kilowatts and rise the same way for every unit at this rating. The figures below are calculated from the nameplate, not a manufacturer flow curve.

Tempra 24 calculated flow by temperature rise
Temperature rise	Calculated flow (GPM)
35°F	4.59
45°F	3.57
55°F	2.92
65°F	2.47
75°F	2.14

Published standard Source: Calculated from the published 24 kW nameplate rating using GPM = kW x 3412 x 0.98 / (rise x 8.33 x 60). Not a manufacturer flow curve.. Modulation changes how smoothly the unit reaches this ceiling flow and holds outlet temperature while doing it, not the ceiling itself.

Who does the Tempra 24 suit?

This unit suits a household that has already cleared the same 125 A design-load question any 24 kW electric tankless unit requires, and that additionally cares about temperature stability when a dishwasher, washing machine, or second bathroom cycles on mid-shower. Proportional modulation is built to reduce the temperature swing in that scenario, sometimes called the cold water sandwich, by adjusting output continuously rather than stepping between fixed element stages.

Who should not buy the Tempra 24?

Anyone hoping modulation lowers the electrical requirement should not buy this expecting that: the 100 A draw and 125 A design load are fixed by the 24 kW, 240 V nameplate and do not change with the control technology. A cold-inlet household running a 65°F to 75°F rise should still expect only 2.14 to 2.47 GPM calculated, same as any other 24 kW unit, so modulation does not buy back the flow that a bigger unit or a lower rise would.

What does installing the Tempra 24 actually involve?

Installation follows the same path as any 24 kW electric tankless unit: an electrician runs a load calculation confirming 125 A of spare design-load capacity, then wires the circuits according to Stiebel Eltron's installation manual and sizes conductor and breaker under NEC Table 310.16. Where the panel does not have the headroom, a subpanel or service upgrade is the next step, and that is priced and scoped by the electrician; houseprojectcalc.com is the resource for that cost question, not this page.

Turn the breaker off and confirm with a meter before opening the unit. Both legs of the 240 V circuit are live regardless of which manufacturer built the box, and an unsubmerged element must never be energized.

How we researched this

We did not test this heater in person. This page is built from Stiebel Eltron's published nameplate rating of 24 kW at 240 V, current and design-load figures calculated from that rating with Ohm's law and NEC 422.13, and the same flow-by-rise formula applied consistently across this category. The modulation description reflects how Stiebel Eltron describes the Tempra line's control approach; we did not independently verify temperature stability, and we read verified owner reviews for how that control approach holds up in practice.

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Frequently asked questions

How many amps does the Stiebel Eltron Tempra 24 draw?: The Tempra 24 is rated 24 kW at 240 V, which is 100 A of continuous current using P = I x V, identical to any other 24 kW electric tankless unit. NEC 422.13's continuous-load rule adds a 125 percent factor for the circuit and breaker, bringing the design load to 125 A. Proportional modulation does not change this figure.
What does proportional modulation mean on the Tempra 24?: Stiebel Eltron describes the Tempra line as adjusting heating element output continuously to match the flow the unit senses, rather than switching fixed-wattage elements on and off in stages. The intent is a steadier outlet temperature as demand changes mid-use, for example when a second fixture opens. It does not change the unit's 24 kW nameplate rating or its electrical draw.
Does the Tempra 24 draw less power than a fixed-element 24 kW heater?: No. Current draw is set by the nameplate kilowatt and voltage rating, not by the control method. A Tempra 24 and a fixed-element 24 kW competitor both draw 100 A continuously and both carry a 125 A NEC design load. Modulation affects how smoothly output changes, not how much power the unit is rated to use.
How much flow does the Tempra 24 deliver at a 55 degree rise?: Calculated from its published 24 kW rating, the Tempra 24 works out to about 2.92 GPM at a 55°F rise. This is the same calculated figure as any other 24 kW, 240 V electric tankless unit, since flow output is a function of kilowatts and rise rather than the control technology used to deliver it.
Can the Tempra 24 run on a 100 amp panel?: Not on its own with any margin. A 125 A design load leaves essentially nothing for the rest of a 100 A panel, so this unit needs a larger service, most commonly 200 A, with a licensed electrician's load calculation confirming spare capacity before installation.
Does the Tempra 24 help with the cold water sandwich effect?: Stiebel Eltron's proportional modulation is built to reduce the temperature swing that happens when demand changes mid-use, which is one contributor to the cold water sandwich effect on any tankless unit. It addresses output stability, not the separate delay caused by hot water already in the pipe cooling before a fresh draw reaches the tap.

The control technology does not change the electrical requirement. Confirm 125 A of spare design-load capacity with a licensed electrician before ordering, turn the breaker off and verify with a meter before opening the unit, and never energize an element that is not fully submerged.