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

Rheem RTEX-13 vs Rinnai RU199iN

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 comes out ahead by a clear margin (4.1 vs 4.5). The gap is mostly about Large households with gas service that need whole-home hot water for multiple bathrooms at once. — read the strengths below before deciding.

Rheem RTEX-13
Ranked #5 in Best Tankless Water Heaters
Rheem RTEX-13
2 sourcesall derived$271.48as of Aug 1

The Rheem RTEX-13 is the best bang for the buck, Bob Vila's value choice and Reviewed's budget electric unit, praised for a '99 percent efficiency rating' at the lowest price in this group. At about 3.17 GPM it's a point-of-use heater designed, as Reviewed notes, 'to support one to two appliances in a single location, such as a shower in the bathroom.' It won't run a whole house. For a remote bathroom, an addition, or a booster, its compact size, efficiency, and low cost make it the obvious affordable choice.

Strengths
  • — Lowest price of the group — excellent point-of-use value
  • — Roughly 99% energy efficiency with self-modulating control
  • — Compact 13 kW unit easy to install near a single fixture
Watch-outs
  • — Only ~3.17 GPM — supports one to two fixtures, not a whole home
  • — Not suitable as a primary whole-house heater in most homes
  • — Flow drops further with cold inlet water
$271.48 · Check Price on AmazonFull review →
Rinnai RU199iN
Higher ratedRanked #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 →

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

Rheem RTEX-13

The Rheem RTEX-13 is the smallest and cheapest unit here, a point-of-use heater at about 3.17 GPM versus the whole-home flow of the Stiebel Eltron Tempra 36 Plus and EcoSmart ECO 27, and far below the gas Rinnai RU199iN and Takagi T-H3-DV-N. It's not a whole-home replacement, but it's the value leader for single-fixture jobs.

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.

Specs side-by-side

SpecRheem RTEX-13Rinnai RU199iN
FuelElectricNatural gas
Flow RateUp to ~3.17 GPMUp to 11 GPM
Efficiency~99%0.95
Power13 kW—
BTU2.3-2.3 GPM15,000 - 199,000
TypeElectricCondensing
InstallationIndoor, point-of-useIndoor
Dimensions8.25"W x 12.62"H18.5"W x 30.11"H
← See the full ranking of best tankless water heaters