Tempra 12 Plus: capacity and installation fit
The Tempra 12 Plus brings the Plus controls to the smallest output level in the Tempra family. Its single electrical feed sets it apart from the larger models. It is worth evaluating for a modest, carefully measured hot-water demand when the owner wants automatic flow management as well as electronic temperature control.
This guide covers Stiebel Eltron Tempra 12 Plus, item 239219. It is an electric tankless water heater, with output determined by power and temperature rise rather than stored gallons. Water Heating Experts helps Palm Beach Gardens, Jupiter and nearby homeowners assess the model and the work needed to install it. See our Stiebel Eltron overview for the family comparison.
What the Plus controls add
The Tempra 12 Plus includes Advanced Flow Control. If demand exceeds the available heating capacity, it can reduce water flow to maintain the selected outlet temperature. It also has two temperature memory presets and a display showing flow rate and operating capacity. These are useful controls, but the model still needs enough output for the way you want to use hot water.
The Tempra 12 Trend has the same published heating input at each voltage. Plus adds flow management and display functions rather than a higher kW rating. Both families modulate heating power. Choosing Plus therefore involves deciding how you want the heater to respond near its capacity limit, as well as selecting the correct size.
Electrical requirements: 240 V versus 208 V
| Specification | 240 V | 208 V |
|---|---|---|
| Rated input | 12 kW | 9 kW |
| Maximum current draw | 1 × 50 A | 1 × 44 A |
| Manufacturer minimum recommended double-pole breakers | 1 × 50 A | 1 × 50 A |
| Minimum recommended copper wire runs | 1 × 8/2 AWG | 1 × 8/2 AWG |
The manufacturer recommends a 100 A minimum main service, depending on total electrical load. This is separate from the branch-circuit requirements. The standard ratings are for single-phase, 50/60 Hz supply; the manual also addresses applicable 208 V three-phase arrangements for certain sizes. A qualified electrician must confirm the actual supply and design the installation for the specific model.
Stiebel Eltron specifies copper conductors rated at least 75°C and sizing for less than 3% voltage drop under load. Existing tank-water-heater wiring cannot be assumed suitable. Include the home’s other major loads and planned electrical additions in the assessment. These comparison figures are not directions to change breakers or conductors yourself.
Flow examples with stated water temperatures
For this model, flow management is especially relevant when a second fixture opens. The 12 Plus can reduce throughput as it reaches its heating limit, so a stable temperature does not necessarily mean the original shower or faucet flow will continue. Decide whether the available flow is comfortable for your intended uses before selecting the smallest size.
| Inlet → outlet temperature | Manufacturer 220–240 V row | 208 V |
|---|---|---|
| 77°F → 113°F (36°F rise) | 2.27 GPM | 1.70 GPM |
| 59°F → 113°F (54°F rise) | 1.51 GPM | 1.14 GPM |
These are the manufacturer’s published flow-table examples. Its higher-output rows are labeled 220–240 V; electrical input in our specification table is specifically stated at 240 V. The example inlet temperatures are not a measurement of your home. Higher requested outlet temperatures or colder inlet water reduce available flow.
List the showers, faucets and appliances you expect to operate together. Fixture flow and overlap matter more than bathroom count alone. Water at a mixed faucet can also have a different flow from water passing through the heater. Tell us which uses your current system struggles to support so we can compare the replacement against a concrete demand.
Dimensions, efficiency and service access
The current technical data table lists 0.94 UEF, a minimum activation flow of 0.37 GPM and a weight of 13.5 lb. Cabinet dimensions are 16⅝ inches wide × 14½ inches high × 4⅝ inches deep, with ¾-inch NPT water connections. UEF is a standardized comparison value, not a promise of a particular bill reduction.
Allow the manual’s 5 inches of service clearance on all sides, along with room for connections. Plan a protected location away from freezing and routine splashing. Accessible plumbing matters for future maintenance, including attention to scale and the inlet screen. The installation manual is the reference for the installer’s final layout.
Keep the receipt and installation record and follow the supplied registration directions. The manufacturer’s limited warranty lists seven years for qualifying leakage and three years for qualifying defects, subject to its terms; field labor is not included. Discuss water quality and maintenance needs when planning the installation.
Compare nearby sizes before deciding
The 15 Plus moves to two circuits and 14.4 kW at 240 V; the 20 Plus increases that to 19.2 kW. Those are meaningful output steps, accompanied by different electrical requirements. A smaller heater can be appropriate when the measured demand fits, but choosing it only to minimize electrical work can leave you dissatisfied with simultaneous flow.
Read the Tempra 15 Plus and Tempra 20 Plus guides, compare the matching Trend model above, or browse the full water-heater model catalog. If electrical changes affect the project significantly, compare a suitable electric storage water heater as part of the complete installation estimate.
Tempra 12 Plus questions
Can the Tempra 12 Plus supply several fixtures at once?
Only when their combined demand fits the available output at the required temperature rise. At a 77°F inlet and a 113°F outlet, the manufacturer lists 2.27 GPM on its higher-voltage row. Advanced Flow Control may reduce flow if demand goes beyond the heater’s capacity.
Does Advanced Flow Control increase heating output?
No. It manages water flow when demand exceeds the heater’s available capacity. Reducing flow helps maintain temperature, but it cannot supply the same high flow as a larger heater under every condition. Select the model for the simultaneous demand you want it to handle.
Does the Tempra 12 Plus have temperature presets?
Yes. Tempra Plus has two stored temperature presets, along with a flow-rate display. Presets make an existing setting easier to recall; they do not change the unit’s maximum heating capacity or resolve an undersized installation.
Will tankless eliminate the wait at distant taps?
Water already in the pipe must still travel to the fixture. Heater output, pipe length and any recirculation arrangement are separate considerations. Tell WHE which taps have long waits so the estimate addresses that concern specifically.
What information helps with an installation estimate?
Send the current heater’s label, a wide installation photo, your location and a description of simultaneous hot-water use. Mention Tempra 12 Plus. We review the plumbing and electrical requirements before confirming equipment availability, the proposed work and scheduling.
Request a Tempra 12 Plus installation estimate
For water-heater installation or replacement, call 561-602-9062, text WHE or request a free installation estimate. Share the project details so we can discuss a suitable model and installation scope.
Sources checked October 17, 2026: Tempra Plus family information and Tempra technical specifications, revision 6.2025, with the manufacturer manual, flow table and warranty linked above. Confirm the exact unit label and current installation documents before work begins.