Verdict
All guidesResearchMethodologyAboutContact
Head-to-head · Best Tankless Water Heaters

Rinnai RU199iN vs Stiebel Eltron Tempra 36 Plus

Which is the better buy? Side-by-side on rating, price, strengths, and watch-outs — with the published ratings we averaged to get there.

Verdict is reader-supported. As an Amazon Associate we earn from qualifying purchases. Some links on this page are affiliate links — if you click through and buy, we may earn a small commission at no extra cost to you. Our ratings are sourced from independent publications, not sponsors.
The short answer

Rinnai RU199iN and Stiebel Eltron Tempra 36 Plus score essentially the same (4.5 vs 4.5). Pick the one whose trade-offs match your priorities — the strengths and watch-outs below are where they actually differ.

Rinnai RU199iN
Ranked #2 in Best Tankless Water Heaters
Rinnai RU199iN
2 sourcesall derived$1,532.8as of Aug 1

The Rinnai RU199iN is the best overall gas tankless water heater for whole-home use, good for up to 11 GPM and 199,000 BTU, enough hot water for up to five appliances or a 3-4 bathroom house running at once. Bob Vila named the Rinnai SENSEI line its best overall, and reviewers consistently praise the condensing efficiency (0.95 UEF, which qualifies for the federal tax credit) and Wi-Fi control. It is the priciest pick and needs gas service and condensing venting. For a busy household in any climate, nothing here matches its capacity.

Strengths
  • — Industry-leading 11 GPM flow rate handles a 3-4 bathroom home at once
  • — Condensing design with a 0.95 UEF qualifies for the 30% federal tax credit
  • — 199,000 BTU output keeps up even in cold inlet climates
Watch-outs
  • — Highest upfront and installation cost of the group
  • — Requires gas service and proper condensing venting
  • — Overkill for a small home or apartment
$1,532.8 · Check Price on AmazonFull review →
Stiebel Eltron Tempra 36 Plus
Ranked #1 in Best Tankless Water Heaters
Stiebel Eltron Tempra 36 Plus
3 sources2 derived$712.73as of Aug 1

The Stiebel Eltron Tempra 36 Plus is the clear frontrunner for whole-home electric tankless heating, good for up to 7.5 GPM from its 36 kW heating element. This Old House rated the Stiebel Eltron electric line 4.4/5, and Bob Vila named it best electric, both praising the silent operation and the Advanced Flow Control that dynamically reduces flow rather than letting cold-water sandwiching happen when demand exceeds capacity. It needs serious electrical service and performs best in moderate climates. For an all-electric home, it is the top whole-house pick.

Strengths
  • — Best whole-home electric option, up to 7.5 GPM at 36 kW
  • — Advanced Flow Control throttles flow to prevent cold-water sandwiching
  • — Silent operation with no combustion, venting, or CO risk
Watch-outs
  • — Needs substantial electrical service — often a panel upgrade
  • — Flow rate drops in cold climates with high temperature rise
  • — No federal gas tax credit (electric)
$712.73 · Check Price on AmazonFull review →

Derived means the reviewer published no score, so one was inferred from their written verdict. Everything else is a number the publisher printed. How we rank.

How they stack up

Rinnai RU199iN

The Rinnai RU199iN is the highest-capacity unit here, with an 11 GPM gas flow rate that dwarfs the electric Stiebel Eltron Tempra 36 Plus (7.5 GPM), EcoSmart ECO 27, and Rheem RTEX-13. Only the gas Takagi T-H3-DV-N approaches it, and the RU199iN edges it on UEF efficiency. It costs the most upfront and, unlike the electric units, requires gas and condensing venting.

Stiebel Eltron Tempra 36 Plus

The Stiebel Eltron Tempra 36 Plus is the best whole-home electric unit, with a 7.5 GPM flow rate that beats the EcoSmart ECO 27 and Rheem RTEX-13 but trails the gas Rinnai RU199iN and Takagi T-H3-DV-N. Its Advanced Flow Control is a feature neither the EcoSmart nor the Rheem offers, trading a brief flow reduction for consistently hot water.

Specs side-by-side

SpecRinnai RU199iNStiebel Eltron Tempra 36 Plus
FuelNatural gasElectric
Flow RateUp to 11 GPMUp to 7.5 GPM
BTU15,000 - 199,000—
Efficiency0.95—
TypeCondensingTankless Electric
InstallationIndoor—
Dimensions18.5"W x 30.11"H—
Power—36 kW
← See the full ranking of best tankless water heaters