Updated October 2026 · 5 heaters, no paid placements

Best Whole-House Tankless Water Heaters in 2026: Gas and Electric

One heater for every tap in the house, gas or electric: these five are the best-rated units whose own listings claim whole-house use. Ranked on buyer ratings, review volume and specs, with an honest note on what "whole house" really buys you in January.

See the ranking

In short

Our top pickMIZUDO 199,000 BTU Natural Gas Indoor9.2/10. The one we'd start with.$1,199 on Sep 30, 2026, may have changed

The crowd favouriteRinnai RU199iN Condensing388 buyer reviews, 7.8/10. Plenty of owners to learn from.See current price

The most flow on paperRheem RTGH 8.4 GPM Natural Gas Indoor8.4 GPM per the listing, 7.3/10. The biggest figure among the rest.$1,168.99 on Sep 30, 2026, may have changed

If one unit has to survive the 6:45 shower rush, start with the MIZUDO 199,000 BTU Natural Gas Indoor. The other four mix gas and electric, so your fuel and your panel narrow the list before we do. Variants share a slot, so you see five different heaters, gas and electric side by side.

Written from each listing's specs and buyer reviews, not from our own use · How we rate

The ranking in detail

Gas tankless water heaters · MIZUDO · Top pick

MIZUDO 199,000 BTU Natural Gas Indoor

9.2Excellent · out of 10

Best for: swapping a 50-gallon tank for a house with three bathrooms

Stated maximum flow: 10.3 GPM
Stated gas input: 199,000 BTU/h
The listing claims whole-house use

The catch: Expect less than 10.3 GPM when the groundwater is cold.

4.4/5 from buyers307 buyer reviews$1,199 Price on Sep 30, 2026 · may have changed

See it on Amazon ↗Read the reviewaffiliate link to Amazon.com

Gas tankless water heaters · Rinnai · Runner-up

Rinnai RU199iN Condensing

7.8Very good · out of 10

Best for: a busy house where two showers and the dishwasher overlap

Stated maximum flow: 11 GPM
Natural gas, indoor mounting (listing)
The listing claims whole-house use

The catch: No ±1 °F temperature hold claimed for the Rinnai, while most units here state one.

4.4/5 from buyers388 buyer reviewsSee current price ↗

See it on Amazon ↗Read the reviewaffiliate link to Amazon.com

Gas tankless water heaters · FOGATTI · Top 5 pick

FOGATTI Outdoor Propane Tankless

7.6Very good · out of 10

Best for: a mild-climate house with no easy vent route

Stated gas input: 120,000 BTU/h
Propane, outdoor mounting (listing)
The listing claims whole-house use

The catch: Its 4.0/5 buyer rating is the lowest of these five.

4/5 from buyers166 buyer reviews$529.99 Price on Sep 30, 2026 · may have changed

See it on Amazon ↗Read the reviewaffiliate link to Amazon.com

Gas tankless water heaters · Rheem · Top 5 pick

Rheem RTGH 8.4 GPM Natural Gas Indoor

7.3Good · out of 10

Also available as: RTGH-95DVLN-3 Natural Gas Indoor (9.5 GPM) · RTGH 9.0 GPM Natural Gas Indoor (9 GPM)

Best for: a two-bathroom house with one shower running at a time

Stated maximum flow: 8.4 GPM
Stated gas input: 157,000 BTU/h
The listing claims whole-house use

The catch: With 60 buyer reviews, it's early days for that average.

4.4/5 from buyers60 buyer reviews$1,168.99 Price on Sep 30, 2026 · may have changed

See it on Amazon ↗Read the reviewaffiliate link to Amazon.com

Electric tankless water heaters · CAMPLUX · Top 5 pick

CAMPLUX 27 kW Electric, 240V

7.2Good · out of 10

Best for: a home without gas and with a big panel

Stated heating power: 27 kW
Stated voltage: 240 V
The listing claims whole-house use

The catch: 27 kW at 240 V is about 113 A: check the panel first.

4.3/5 from buyers141 buyer reviews$302.62 Price on Sep 30, 2026 · may have changed

See it on Amazon ↗Read the reviewaffiliate link to Amazon.com

Product images: Amazon listings

Best rated by fuel

The best-rated unit of this ranking for each fuel its listing states. Start from the fuel your house already has, then read across.

Natural gas	MIZUDO 199,000 BTU Natural Gas Indoor (#1) · 9.2/10 · 10.3 GPM, 199,000 BTU/h
Propane	FOGATTI Outdoor Propane Tankless (#3) · 7.6/10 · 120,000 BTU/h
Electric	CAMPLUX 27 kW Electric, 240V (#5) · 7.2/10 · 27 kW

How to choose

Count simultaneous fixtures, not bathrooms. A three-bathroom house where nobody showers at the same time needs less than a two-bathroom house with a 6:45 rush. Add up what really overlaps, dishwasher and washer included.
Read the rise behind the headline GPM. Many listings quote their maximum flow at a 35 °F rise. Northern groundwater in January asks for far more, so check the maker's chart at your own rise before you trust the number in the title.
Let the house pick the fuel. Gas needs a line and a vent with spare capacity; electric needs a panel that can carry 75 A or more. Price the work your house needs for each, then compare heaters inside the fuel that wins.

What "whole house" means on a listing

"Whole house" is a seller's claim, not a size. 31 reviewed listings make it: gas units stating 4.23 GPM to 11 GPM and electric units from 18 kW to 36 kW. Whether one of them carries your house depends on how many fixtures run at once and how cold the water comes in, not on the word in the title.

Here's the shower maths. Two showers at the 2.0 GPM our calculator uses is 4.0 GPM; add the dishwasher and you're at 5.5 GPM. With 42 °F groundwater (the calculator's northern-US figure) heated to 105 °F, that's a 63 °F rise, while many headline GPM figures are quoted at a gentler 35 °F rise (five of the listings here say so in their own text). Read the maker's flow chart at your rise, not the number in the title.

Gas or electric? A gas unit asks for a gas line and a vent; a whole-house electric unit asks your panel for about 75 A at 18 kW and 150 A at 36 kW (kW ÷ 240 V). Our whole-house electric tankless ranking and gas tankless ranking go deeper on each side, and the point-of-use vs whole-house guide helps when the real problem is one far-off sink.

Comparison table

All 5 on one screen. Tap a column header to sort by what matters at 6:45 on a weekday: flow, power or price.

Comparison table: Best Whole-House Tankless Water Heaters in 2026: Gas and Electric

MIZUDO 199,000 BTU Natural Gas Indoor	MIZUDO	9.2	$1,199^†	Natural gas	10.3 GPM	199,000 BTU/h	120 V	Indoor	307
Rinnai RU199iN Condensing	Rinnai	7.8	See current price	Natural gas	11 GPM	Not stated	Not stated	Indoor, condensing	388
FOGATTI Outdoor Propane Tankless	FOGATTI	7.6	$529.99^†	Propane	Not stated	120,000 BTU/h	120 V	Outdoor	166
Rheem RTGH 8.4 GPM Natural Gas Indoor	Rheem	7.3	$1,168.99^†	Natural gas	8.4 GPM	157,000 BTU/h	Not stated	Indoor, condensing	60
CAMPLUX 27 kW Electric, 240V	CAMPLUX	7.2	$302.62^†	Electric	Not stated	27 kW	240 V	Not stated	141

^† Prices as of Sep 30, 2026; they may have changed. The button always shows today's price.

How we rank

Every heater gets a score out of 10 from its exact listing. We look at what buyers give it, how many of them there are, and how completely the seller documents the specs and the warranty, then at how it stacks up against the other heaters in the list. On an exact tie, the listing slug settles the order.

We haven't installed or run these heaters ourselves, and a commission never moves a rating or a rank.

Read the methodology →Affiliate disclosure

45 % buyer rating, damped when a listing has fewer than 50 reviews.
35 % review volume, on a logarithmic scale up to 5,000 reviews.
20 % documentation: feature bullets, images and stated brand of the listing.
Flow, BTU/h input, kW and voltage show up only when the exact listing states them. A headline GPM is not your winter flow, and we measure nothing ourselves.
One slot per listing family: variants of one parent listing, which usually share one review pool, count once and are listed under the best-rated variant.
Prices carry the date we recorded them. They may have changed since; the button shows today's offer.

Frequently asked questions

Which is the best whole-house tankless water heater in 2026?

Our pick is the MIZUDO 199,000 BTU Natural Gas Indoor, at 9.2/10 (excellent). It has 307 buyer reviews averaging 4.4/5, and its listing states 10.3 GPM and 199,000 BTU/h. Next in line: the Rinnai RU199iN Condensing at 7.8/10.

How is this ranking built?

We start from 31 complete tankless units, gas or electric, whose own listing claims whole-house (or whole-home) use, each with a buyer review record. Each one gets a rating out of 10: 45 % buyer rating, 35 % review volume and 20 % how completely the listing documents its specs. Variants of one listing family (same parent listing) share a single slot, so you see 5 different heaters rather than one heater in 5 sizes.

What size tankless water heater do I need for a whole house?

Count the fixtures that really run together, then use your winter rise. As a planning example, two showers and a dishwasher is about 5.5 GPM; at a 63 °F rise that's about 173,000 BTU/h of heat, so about 211,000 BTU/h of gas input at 82 % efficiency, or about 51 kW electric. That is more than any electric unit here states (36 kW at most), which is why electric whole-house units suit warmer groundwater or fewer showers at once. The flow-rate calculator runs your own numbers.

Can one tankless water heater run two showers at once?

Yes, if it's sized for it. Two showers at 2.0 GPM each need 4.0 GPM at your winter rise. 21 of the 31 eligible listings state a maximum flow of 4.0 GPM or more, but that maximum is usually quoted at a mild rise, so check the chart before you count on it in January.

Is a gas or electric whole-house tankless water heater better?

Gas makes more hot water per unit: the DOE Energy Saver page and A. O. Smith both say gas models deliver higher flow than electric ones. Electric skips the vent and the gas line but leans hard on your panel. Pick the fuel your house already has the capacity for, then the model.

How much does a whole-house tankless water heater cost?

Among the 28 eligible listings with a price we recorded, the box alone ran from $192.99 (Garvee 27 kW Electric, 240V) to $1,454.31 (Rheem RTGH-95DVLN-3 Natural Gas Indoor), with a median of $560.49, on Sep 30, 2026. Prices move, and the installer's bill comes on top, and it is often the bigger number.

Are the prices up to date?

Each price is the one we recorded on Sep 30, 2026, and it may have changed since. The button always opens the exact listing with today's price and seller.

Have you installed these water heaters yourselves?

No, we haven't installed them in a house of our own. The ratings come from what buyers say and from the specs stated in each exact listing, weighed with a formula we publish.

Tankless flow-rate calculator →Buying guide: how to choose a tankless water heater →Best Tankless Water Heaters in 2026 →Best Outdoor Propane Tankless Water Heaters in 2026 →Best Whole-House Electric Tankless Water Heaters in 2026 →Best High-Efficiency Condensing Tankless Water Heaters in 2026 →Best Gas Tankless Water Heaters in 2026 →All rankings →Comparison tool →

Gas tankless water heaters →Electric tankless water heaters →Rheem →Rinnai →CAMPLUX →MIZUDO →Buying guides →