Stiebel Eltron Tempra 36 Plus 36kW Electric Tankless Water Heater

The Stiebel Eltron Tempra 36 Plus 36kW Electric Tankless Water Heater is the flagship of Stiebel's residential electric tankless lineup. 36,000W (36 kW) heating, ~6 GPM at 35°F rise (cold-water climates) up to ~8 GPM at 70°F+ inlet, 99% UEF, 7-year warranty. The Tempra 36 Plus is the right pick when natural gas is unavailable, heat-pump install is blocked, and you want endless hot water without a tank.

Headline specifications

• Type: whole-house electric tankless, 240V three-phase or split-phase
• Power input: 36 kW (3 × 12 kW elements)
• Maximum flow rate: ~6 GPM at 35°F rise; ~8 GPM at 50°F rise
• Energy Factor (UEF): 0.99
• Min activation flow: 0.5 GPM
• Temperature range: 86°F – 140°F (precise digital control)
• Warranty: 7-year heat exchanger, 3-year parts
• Dimensions: 18" H × 17" W × 5" D (extremely compact)
• Weight: 18 lbs (vs ~50 lbs for gas tankless)
• Electrical: requires 3× 40-amp 240V circuits (150-amp service typically required)

Who this model is for

Right buyer profile: all-electric households without natural gas service, homes where heat-pump install is blocked (insufficient ambient air, no basement, low ceiling), buyers who want endless hot water in a tank-free format, properties with 200-amp electrical service that can accommodate the 150-amp draw. Snowbelt-state homeowners with very cold inlet water (35°F – 50°F): the 36 kW capacity is the only electric tankless that supports a full shower at 110°F under those conditions. Stiebel Tempra 24, 29, 32 — all cap out at 4–5 GPM at 35°F rise; only the Tempra 36 hits 6 GPM.

Wrong product if: you have natural gas (use gas tankless instead — far cheaper to operate), your electrical service is 100-amp or 150-amp (cannot accommodate 150-amp draw), your basement supports a heat pump (heat pump is 3x cheaper to operate than resistance electric, tankless or not).

Where the Tempra 36 Plus beats the alternatives

Vs AO Smith Voltex 50 HP ($1,649): Voltex 3.45 UEF vs Tempra 0.99 UEF — heat pump uses one-third the electricity for the same heat output. For homes where heat pump fits, heat pump wins on operating cost ($250 vs $700+/year for typical 4-person household). For homes where heat pump can't fit, Tempra is the right pick.

Vs EcoSmart ECO 27 ($549): EcoSmart 27 kW (~$700 less). Tempra 36 has more capacity (36 kW vs 27 kW) — 1.3x more peak flow at very cold inlet. Stiebel build quality and digital temperature control are noticeably better. EcoSmart wins on price; Stiebel wins on cold-climate performance and reliability.

Vs gas tankless (Rinnai RU199iN): if you have natural gas, gas tankless is the right pick. Tempra is only for all-electric homes.

Vs gas/electric tank: Tempra saves 25–40 sq ft of floor space. Endless hot water. No tank failure risk. 7-year warranty.

Where it falls short

150-amp draw is the big constraint. Most US homes have 100-amp or 150-amp service. Adding 36 kW tankless typically requires service upgrade to 200-amp + dedicated subpanel — $1,800–$3,500 in electrical work on top of the unit cost.

0.99 UEF resistance electric is excellent for resistance — but heat pump at 3.45 UEF is 3.5x more efficient. For homes that can accommodate a heat pump, the Tempra's operating cost ($700–$1,000/year for 4-person household) is hard to justify.

6 GPM at 35°F rise is the limit. Two simultaneous showers in cold-water months will exceed capacity. The Tempra 36 is whole-house only for 3–4 person households at moderate concurrent demand.

7-year warranty is shorter than gas tankless (15-year heat exchanger on flagships) and shorter than heat pump (10-year).

No WiFi or smart-home integration.

Install considerations

Verify 200-amp service or budget for upgrade. 3× 40-amp 240V dedicated circuits required (typically dedicated subpanel). 3/4" cold-water inlet, 3/4" hot-water outlet. Wall-mount (very compact). Licensed electrician + plumber. Permit required.

Install cost: $800–$1,400 for the unit install assuming 200-amp service exists; $2,500–$5,000 if service upgrade required.

Maintenance

• Annual filter cleaning
• Annual descaling in hard-water regions (no acid descaling — Stiebel recommends physical disassembly + cleaning)
• Element inspection at year 5
• Electrical connection torque check annually

Bottom line

The Stiebel Eltron Tempra 36 Plus is the flagship electric tankless — 36 kW, 6 GPM at cold inlet, 0.99 UEF, 7-year warranty. Right pick for all-electric households where natural gas is unavailable and heat pump can't fit. Demands 200-amp service. For homes that can accommodate a heat pump, the AO Smith Voltex 50 HP or equivalent uses one-third the electricity and is the better long-term economics pick. For budget-conscious electric tankless, EcoSmart ECO 27 at $700 less is the alternative.