Best RV Tankless Water Heater (2026)

Plumbing Picks is reader-supported. As an Amazon Associate, we earn from qualifying purchases at no extra cost to you.

Quick answer from a licensed plumber: Match the heater to your opening first. The Suburban ST-60 is the pick for a standard 6-gallon side-wall cutout, and it needs a separate door. The Furrion FWH09AFA-AM lists the widest range of existing openings. The Camplux RS264B has the highest maker flow figure at a stated rise (2.64 GPM at 45°F), but its manual conflicts with itself. All four are propane, 12 V, and their makers require qualified installation.

Our take: for a standard 6-gallon opening, the Suburban ST-60: Check the Suburban ST-60 on Amazon. For an odd-size opening, the Furrion: Check the Furrion FWH09AFA-AM on Amazon. The Camplux and Girard are below with their limits.

This guide covers tankless heaters built for RVs: outside-wall, vented through the wall, propane, 12 V. It does not cover house propane heaters, which are in our best propane tankless water heater guide, or natural gas units (see the best gas tankless water heater guide). For brand-level differences in house models see our tankless water heater brands comparison. Portable camping shower heaters are a different product.

RV Tankless Water Heaters Compared: Flow, Gas and Power

Model	Max input (BTU/h)	Flow (maker figure and basis)	Minimum flow to fire	12 V draw (maker)	Amazon listing
Suburban ST-60	60,000	No flow at a set rise in the documents we read	0.7 GPM	Under 10 A total	Third party (CWDS)
Suburban ST-42	42,000	1.5 GPM at a 50°F rise (70°F in, 120°F out), per the sell sheet	0.7 GPM	Under 10 A total	Third party (CWDS)
Camplux RS264B	65,000	2.64 GPM at a 45°F rise, per the manual	0.32 GPM	Under 3 A (manual also names 6 A and 10 A fuses)	Sold by Amazon
Furrion FWH09AFA-AM	60,000	Up to 2.4 GPM, no rise stated	0.32 GPM	Under 3 A; about 0.25 A idle	Sold by Amazon
Girard GSWH-2	42,000	1.4 GPM at a 50°F rise, 1.0 GPM at a 70°F rise (high heat), per Girard’s 2025 service manual	0.6 to 0.9 GPM (manual conflicts)	Under 3 A; about 0.20 A idle	Third party (Midwest Aftermarket)

Figures are from the maker documents listed under Sources; input is not output. Flow is not comparable across rows: Suburban states its ST-42 figure at a 50°F rise, Girard gives a table from 50°F to 90°F, Camplux states 45°F, and Furrion states none. Stock checked September 29, 2026. Check the seller name at checkout.

Openings, Depth and Doors

Model	Cutout the maker lists	Body size	Retrofit statement	Door
Suburban ST-42, ST-60	13 x 13 in. framed opening	12 1/2 x 12 3/4 x 13 in. (H x W x D)	Sized for existing standard 6-gallon side-wall cutouts (sell sheet)	Suburban door 6285APW (white) or 6285AEB (black), sold separately
Camplux RS264B	12.75 x 12.75 in., at least 20 in. deep	12.6 x 12.5 x 14.74 in. body	Cutout size can replace Atwood and Suburban 6-gallon heaters (manual)	15.2 x 15.2 in. door in the box (listing)
Furrion FWH09A family	New: 12 5/8 to 13 in. by 12 3/4 to 13 in., at least 19 3/4 in. deep	12 5/8 x 12 5/8 x 19 1/8 in. body	Existing openings 12 5/8 to 15 in. take the 16 1/8 in. door; larger doors for up to 17 in.	Separate Furrion door (FWH09EA, FWH41EA or FWH46EA); the listing has the heater and wall thermostat only
Girard GSWH-2	13 x 13 in. rough opening, supported on all sides	12.5 x 12.5 x 15.5 in.	Atwood 6-gal (16 1/4 x 12 5/8) and 10-gal (16 1/4 x 15 3/4), Suburban 10-gal (16 1/4 x 16 1/4) need door kit and bracing	Girard door kit by part number (separate part); the listing names only the heater

Measure your opening, the depth behind it and the outside skin before you buy. Camplux wants 4 inches of clearance to combustibles at the sides and top. Furrion and Girard list 1 inch at the top and 0 at the sides. Suburban lists 0 all around.

Best Drop-In for a 6-Gallon Opening

Suburban ST-60 and ST-42 Tankless RV Water Heaters

ST-60: 60,000 BTU/h max, 8,000 min · ST-42: 42,000 max, 8,000 min · 12 V DC, total input current under 10 A · needs 0.7 GPM to run · LP gas, 11 in. w.c. rated inlet (10.5 to 14) · 3/8-inch flare gas, 1/2-inch NPT water · casing 12 1/2 x 12 3/4 x 13 in. · framed opening 13 x 13 in. · access door sold separately · 2-year limited warranty

Suburban’s sell sheet says the ST42 and ST60 are sized to fit existing standard 6-gallon water heater side-wall cutouts. The manual’s figure 2 calls for a framed opening about 13 by 13 inches and says a Suburban door has to be installed for proper operation. The door is a separate part: 6285APW in white or 6285AEB in black. The ST-60 listing says the same. Suburban says installation and service must be done by a qualified installer, service agency or the gas supplier.

Suburban gives one flow figure. Its sell sheet says the ST42 delivers continuous water up to 120°F where the intake water is not below 70°F, at 1.5 GPM. That is a 50°F rise (our arithmetic). It recommends the ST60 for colder incoming water or winter use but gives no flow figure for it. Suburban’s manual says to review your gas regulator and supply plumbing so they can keep up with the new heater and every other gas appliance, and to add a pipe union in each water line for easy removal. Active freeze protection cycles the burner when the water falls below 41°F, but only with power and gas on. The sell sheet says the child lock stops outlet temperatures above 113°F. The manual says it caps the set point at 122°F and that the factory setting is 113°F. Treat the manual as the rule for your unit.

Suburban documents fit for existing 6-gallon side-wall cutouts
Suburban lists a two-year limited warranty, for the original purchaser with proof of purchase
Suburban says the unit is tested and approved for altitudes up to 4,500 feet
Both Suburban units were listed in stock on September 29, 2026

The door is a separate purchase
On Amazon’s retail page both Suburban links show CWDS, a third-party seller, not Amazon or Suburban. Amazon’s product data listed Amazon.com for the ST-60, so check the seller at checkout
No flow figure for the ST-60 in the documents we read
The warranty pays a service allowance to a recommended Suburban service center; freight and RV transport are the owner’s cost

Verdict: The pick for a standard 6-gallon opening if you want the RV-industry name and a clear cutout statement. Order the door with it.

Check the Suburban ST-60 (60,000 BTU) on Amazon

Check the Suburban ST-42 (42,000 BTU) on Amazon

Check the Suburban 6285APW white door (required) on Amazon

Highest Stated Flow

Camplux RS264B 65,000 BTU RV Tankless Water Heater

65,000 BTU/h · 2.64 GPM at a 45°F rise per Camplux’s manual · 12 V DC, under 3 A per the spec table · LP gas · cutout 12.75 x 12.75 in., at least 20 in. deep · door and wall controller included · needs 0.32 GPM minimum · 95 to 124°F setting range

Camplux states its 2.64 GPM figure at a 45°F rise in both the RS264 and RE264 manuals, which lets you size it against your own inlet temperature. The manual says the cutout size can replace Atwood and Suburban 6-gallon tank heaters. The listing includes a 15.2 by 15.2 inch door. Camplux’s manual says installation and service must be done by a certified service technician, service agency or the gas supplier. It also says not to use the heater without a working carbon monoxide detector in the RV.

This manual has more internal conflicts than the other three, so read your box label. The spec table says the heater was tested to 2,000 feet; the listing says 9,800 feet, and Camplux’s RE264 manual says 4,500 feet. The spec table gives the gas inlet as 10.5 to 14 in. w.c.; the install pages say 11 to 14; the RE264 manual says 8.0 to 13.0. The manual mentions both a 6-amp and a 10-amp fuse. It says the freeze device heats the water to 48°F in one place and runs from 43°F up to 90°F in another. The listing also says up to 3.9 GPM, which the manual does not state. Camplux’s RE264 manual lists 5 A and 4,500 feet, so the RS and RE models are not the same. The Amazon model field says RS264B but the item type says RE264B. Confirm the model with Camplux before you buy.

2.64 GPM at a 45°F rise in both the RS264 and RE264 manuals
Camplux says its cutout size can replace Atwood and Suburban 6-gallon tank heaters
Door and wall controller are in the box per the listing
Sold and shipped by Amazon on September 29, 2026

The manual contradicts itself on altitude, gas pressure, fuse size and freeze temperatures
Camplux wants 4 inches of clearance to combustibles at the sides and top; Suburban and Furrion list 0 at the sides
The listing’s 3.9 GPM and 9,800 feet are not in the manual we read
The Amazon model field and item type name different models (RS264B, RE264B)

Verdict: The pick if you want the highest maker flow figure at a stated rise and a 6-gallon-size cutout. Read your unit’s label, because the manual disagrees with itself.

Check the Camplux RS264B (65,000 BTU) on Amazon

Best for Odd-Size Openings

Furrion FWH09AFA-AM 60,000 BTU Tankless RV Water Heater

60,000 BTU/h · up to 2.4 GPM (no rise stated) · 12 V DC, under 3 A, about 0.25 A with the controller idle · LP gas, 11 to 14 in. w.c. · 0.32 GPM minimum · new cutout 12 5/8 to 13 in. wide and 12 3/4 to 13 in. high, at least 19 3/4 in. deep · tested to 4,500 feet · antifreeze function below 43°F

The Furrion FWH09A family is the one whose manual covers the most opening sizes. For an existing cutout, Furrion lists 12 5/8 to 15 inches wide and 12 11/16 to 15 inches high for its 16 1/8 inch door, and larger door assemblies for openings up to 17 inches. Furrion adds that an existing opening may need adjusting to its new-cutout requirements, using the steps in the door kit. So a worn or oversized 6- or 10-gallon opening is more likely to work. The manual lists the door assembly as packed separately, and the FWH09AFA-AB spec sheet says a door is included in some kits and sold separately. The Amazon listing includes only the heater and wall thermostat, so plan on a separate Furrion door sized to your opening: FWH09EA (16 1/8 x 16 1/8 in.), FWH41EA (16 1/8 x 18 1/8 in.) or FWH46EA (18 1/8 x 18 1/8 in.). Furrion’s manual says installation and service must be done by a qualified installer, service agency or the gas supplier, and that no one may use the heater without a working carbon monoxide detector in the RV.

Its body is about 19 inches deep, the deepest of the four, and Furrion wants at least 19 3/4 inches behind a new cutout (Camplux asks for at least 20), so measure the space behind the opening. Furrion states no flow at a temperature rise. Its 2.4 GPM is a maximum flow. Furrion’s manual says the antifreeze function only runs with the heater switch, 12 V power and gas all on, and that it protects the heater but not the RV plumbing. Furrion says it will likely be necessary to set the water control valve to minimum in freezing weather. We did not read Furrion’s warranty terms.

Furrion lists existing-cutout sizes up to 15 in. for its standard door
Furrion documents both new and existing cutouts, with door options
Furrion says the unit is tested to 4,500 feet and lists settings for 0 to 2,000 and 2,000 to 4,500 feet
Sold and shipped by Amazon on September 29, 2026

The listing includes only the heater and wall thermostat; the door is a separate Furrion part
Deepest body of the four (about 19 in.); needs at least 19 3/4 in. behind a new cutout
No flow figure at a temperature rise
We did not open the Furrion warranty terms

Verdict: The pick when your existing opening is not the standard size, or you want a door choice. Buy the door that matches your opening.

Check the Furrion FWH09AFA-AM (60,000 BTU) on Amazon

Best Retrofit Instructions

Girard GSWH-2 42,000 BTU Tankless RV Water Heater

42,000 BTU/h · 12 V DC, under 3 A, about 0.20 A idle per the owner’s manual · LP gas, 11 to 14 in. w.c. · body 12.5 x 12.5 x 15.5 in. · rough opening 13 x 13 in. · freeze device on at 38°F, off at 58°F · 95 to 124°F setting range · door kit is a separate Girard part

Girard writes the clearest retrofit rules. Its addendum says the existing Atwood 6-gallon cutout measures 16 1/4 by 12 5/8 inches, but the heater needs a 13 by 13 inch opening whose flange is supported on all four sides by a wooden frame. It adds a 2 by 2 vertical brace and leaves a 3 1/2 inch horizontal gap. For 10-gallon openings (Atwood 16 1/4 by 15 3/4, Suburban 16 1/4 by 16 1/4) it calls for a second brace. It also warns that its conversion door kits do not cover the corners of an Atwood flush-mount door, so the installer has to fabricate a cover. The owner’s manual lists the door kits by part number: 2GWHD and 2GWHDB for a new install or Suburban 6-gallon, 2GWHDA6 for Atwood 6-gallon and 2GWHDAS10 for Suburban or Atwood 10-gallon.

Girard says installation and service must be done by a Girard-recommended installer, service agency or gas supplier, and that the heater is not designed for do-it-yourself installation. Girard’s owner’s manual says the heater needs a minimum of 0.60 GPM for each hot water faucet on one page and 0.90 GPM on another. Girard’s 2025 service manual gives a 0.70 GPM start flow and adds that it “will change to 0.60 GPM” later, without saying when. That manual gives 1.4 GPM at a 50°F rise and 1.0 GPM at a 70°F rise on high heat, and says typical RV flow of 1 to 1.4 GPM gives optimal operation. The listing says 1.5 GPM. The listing seller is a third party, and its included-components line names only the heater. Girard says to use only a Girard door kit with the heater. The owner’s manual says freezing damage is not covered by warranty. It also says bypass kits are not needed, while the older technical manual says they are not recommended.

Girard documents the Atwood 6- and 10-gallon and Suburban 10-gallon retrofit steps
Girard’s owner’s manual lists a door kit part number for each type of opening
Girard states a 38°F on, 58°F off freeze device, with power and gas on
Girard lists about 0.20 A for the idle controller and says to switch the 12 V off in storage

The linked listing is a third-party seller, not Girard or Amazon
Girard door kits are separate parts, and Atwood flush-mount corners need fabrication
Girard’s owner’s manual gives two minimum flows (0.60 and 0.90 GPM), and an older manual gives other freeze temperatures
At a 70°F rise Girard’s table gives 1.0 GPM, so cold inlet water means low flow

Verdict: The pick for an older Atwood opening, if you accept a third-party seller and a separate door kit. Have the installer read the addendum first.

Check the Girard GSWH-2 (42,000 BTU, third-party seller) on Amazon

I send an occasional note when a new guide goes up — repairs worth doing yourself, and the parts that actually last. No spam, no course funnel; written by a licensed Georgia plumber.

12 V Power and LP Supply

Suburban, Furrion and Camplux shut the heater off below 10 V and above 17 V; Girard says its heater will not run below 10 V. Furrion and Camplux say to use a battery or approved converter and list 16 AWG to 40 feet and 14 AWG to about 66 feet for the supply run. Suburban recommends wiring a converter in parallel with the battery to keep the voltage steady. Girard’s older technical manual says older linear converters can cause problems and to wire through the battery. Furrion and Girard also say the controller draws current all the time, so turn the 12 V off in storage or dry camping.

The gas side matters as much as the power. Suburban says to check your regulator and supply plumbing against the new heater and every other gas appliance. Furrion and Camplux say to size the pipe by NFPA 1192 and the Z240 RV series for the added load, and Girard’s technical manual says 11 in. w.c. is the recommended minimum pressure with at least half the gas appliances running. These are LP (propane) heaters, and Furrion, Camplux and Girard say LP gas only. Furrion and Camplux say fuel must be in the gas phase and that butane or mixtures over 10 percent butane must not be used. Ask an RV service shop to test the line before you swap.

Freeze Protection and Winterizing

Model	Freeze feature	Winterizing
Suburban ST-42, ST-60	Burner cycles 5 seconds when water is below 41°F. Needs power and gas on.	Compressed air up to 100 PSI is the preferred drain method. Bypass valves optional. RV non-toxic antifreeze if the coach maker recommends it.
Camplux RS264B	Auto device. Needs power and gas on; controller can be in standby. Manual gives 43°F on and 90°F off in one place, 48°F in another.	Do not exceed 30 PSI compressed air. Drain plug and filter cover. About 1 liter of extra antifreeze to fill the heater.
Furrion FWH09AFA-AM	Runs below 43°F. Off if the heater switch, 12 V power or gas is off. Protects the heater, not the RV plumbing.	Do not exceed 50 PSI. Bypass valve optional, but the heater must be blown out with air first. About 1 liter of extra antifreeze.
Girard GSWH-2	Thermostat starts the burner at 38°F, stops at 58°F (owner’s manual). Needs LP gas and 12 V power, switch left on.	Compressed air or RV antifreeze. The manual says a bypass kit is not required. No air pressure limit stated.

Every maker needs power and gas on for its freeze feature, and Furrion and Girard say it protects only the heater, not the RV plumbing. For house pipes, see our winterize plumbing checklist for the general steps, and follow your RV maker for the coach. Suburban says to drain and flush the heat exchanger with an approved descaling solution each year (manual p7); see our tankless descaling guide for the general method, and follow your maker’s manual.

Who Should Install It, and Propane Safety Lines

All four makers require qualified installation (see the FAQ for their words). Their safety text differs, so we give each in its own terms:

Suburban: Be sure the power is off to the ignition system during any type of refueling and while the vehicle is in motion or being towed. Do not terminate the vent inside add-on rooms, screen porches or onto patios. All combustion air must come from outside, not from occupied spaces. If possible, do not install where any door on the RV can cover or block the vent; if that cannot be avoided, the door’s travel must be limited to keep at least 6 inches between the vent and the open door, and do not run the heater with that door open. Where a slide-out or pop-up can cover the vent, make sure the heater cannot run (thermostat off, power and gas off). Under a slide-out, leave at least 36 inches above the exhaust vent. Do not install with the vent facing the forward end of the coach.
Furrion and Camplux: Exhaust gases contain carbon monoxide; do not breathe or block them. Never use the appliance in enclosed spaces or tents. Turn the appliance off and shut off the fuel supply while parking the RV in an enclosed space such as a garage or repair shop. Never put seating or picnic tables in the path of the exhaust. Do not use the water heater without a working carbon monoxide detector. Both say the operator must turn the gas off at the cylinders before transit and make sure the appliance is off when refueling, traveling through tunnels, parking in garages or carports, or on ferries.
Girard: All combustion air must come from outside the RV and all products of combustion must vent outside. Do not vent it with a system serving another appliance or to an outside enclosed porch. Shut off gas appliances and pilot lights when refueling. Turn the gas off at the LP tank when the vehicle is in motion; gas appliances must never be operated while the vehicle is in motion.

Vent rules also differ, and each is more than one distance. Girard: flue vent at least 9 inches in all directions from any window or opening, not where a door or access panel can cover the air inlet or flue vent, and not venting under an awning, canopy or other enclosure (a roll-out awning without a screen room is allowed). Furrion, measured from the access door: 9 inches from any opening into the vehicle, 36 inches from any motor-driven air intake and 36 inches from any gas tank connection or ventilation; not on the front-facing part of the RV, not on a door or slide-out, and not where a swing door, bag door, slide-out or pop-up can cover the exhaust. Camplux, measured from the cover plate: 1 foot from each side and top of any window, slide-out or opening, 6 feet from a mechanical air inlet and 3 feet from a gas tank connection or ventilation; not on a swing door or where any door, slide-out or pop-up can cover the vent. Suburban’s rules are above. Use the numbers in your unit’s manual and NFPA 1192.

What We Did Not Include

We did not link Truma AquaGo, because our Amazon search on September 29, 2026 found only its parts and doors, not a heater. We did not link the many little-known RV tankless brands, because we could not verify a maker manual for each. That is not a finding against them.

FAQ

Will a tankless RV water heater fit my 6-gallon tank opening?

Often, but measure first. Suburban says its ST42 and ST60 are sized for existing standard 6-gallon side-wall cutouts, and Camplux says its cutout size can replace Atwood and Suburban 6-gallon heaters. Furrion lists existing cutouts from 12 5/8 to 15 inches with its standard door. Girard says an Atwood 6-gallon opening needs a 13 by 13 inch supported flange and a conversion door kit. Each unit needs its own maker’s door, so check whether it is in the box before you order.

Is a tankless RV water heater a do-it-yourself job?

The makers say no in different words. Suburban says installation and service must be performed by a qualified installer, service agency or the gas supplier. Furrion says the same and adds that a qualified person must do any installation. Girard says a Girard-recommended installer, service agency or gas supplier, and not a do-it-yourself project. Camplux says a certified service technician, service agency or the gas supplier. None of the manuals we read says the word RV technician.

How much 12 V power does a tankless RV water heater use?

Makers list limits, not measured draw. Suburban lists total input current under 10 A. Furrion and Girard list under 3 A, with about 0.25 A and 0.20 A when only the controller is on. Camplux lists under 3 A for the RS264 and 5 A for the RE264. All four shut the heater off below 10 V. Furrion and Camplux say to use a battery or approved converter, and Suburban recommends wiring a converter in parallel with the battery.

Can I use a tankless RV water heater in freezing weather?

Only with the freeze feature on and gas and power available. Suburban cycles the burner below 41°F, Furrion below 43°F, Girard from 38°F, and Camplux around 43°F. Furrion and Girard say the feature protects the heater, not the RV plumbing. Suburban says to drain or use RV antifreeze when storing for winter in freezing temperatures.

Do these heaters need a carbon monoxide detector?

Furrion and Camplux say do not use the water heater without a working carbon monoxide detector in the RV. Suburban’s manuals do not include that line, but they warn that a heater that is not maintained or used as intended can produce carbon monoxide, and that soot is a sign of incomplete combustion. The Girard documents we read do not mention carbon monoxide. We would want a working detector with any propane appliance.

Why Trust Plumbing Picks

Plumbing Picks is written by a licensed Georgia journeyman plumber. Every size, rating and spec on this page comes from the manufacturer documents listed below, which we opened and read, or from the Amazon listings we link; nothing here comes from hands-on testing. On September 29, 2026 the Furrion and Camplux heaters and the Suburban door we link were listed in stock and sold by Amazon. We normally link only units sold or shipped by Amazon or the maker. The Suburban ST-60 and ST-42 and the Girard GSWH-2 showed third-party sellers on Amazon’s retail page, so we link genuine-model listings from those sellers. Amazon does not confirm who those sellers are. Where a link goes to Amazon we may earn a commission at no extra cost to you. Nobody pays to be included here. More on who writes this and how we pick.

Sources

Bottom Line

Start with the opening: Suburban for a standard 6-gallon cutout, Furrion for a worn or oversize one, Girard for an older Atwood with the addendum in hand, Camplux if you want the highest stated flow and can confirm the model. Order the door with the heater, check your regulator and LP line, and have a qualified installer do the gas, vent and startup. For a house on propane, see our propane tankless guide.