Natural Gas Navien Water Heater – Why These 5 Models Stand Out

You turn on the shower and wait. And wait. That cold rush before the hot water finally arrives feels like an eternity, especially on a freezing morning. Or maybe you have a big family – one person showers, the next gets lukewarm, and the third gets nothing but cold. Traditional tank heaters waste energy keeping 40 gallons hot all day, then run out when you need them most. Natural gas tankless water heaters solve both problems: endless hot water on demand and lower energy bills. But picking the right model takes more than glancing at BTU numbers.

What makes a great natural gas water heater? It comes down to flow rate, efficiency, installation flexibility, and reliability. For whole‑house use, you need enough gallons per minute (GPM) to run multiple showers and faucets at once. Condensing technology boosts efficiency above 95%, saving gas year after year. And whether you install indoors or outdoors, the unit must handle local weather and venting requirements. The five products here cover the full range – from a stand that meets code for tank heaters to high‑output tankless units that can handle a busy home.

Let’s look at each pick. The Camco stand is an essential accessory for gas tank heaters (not a heater itself). The ThermoMate and APUS offer solid mid‑range performance with smart controls. The Rinnai RX199iN is a premium condensing unit installable almost anywhere. And the FOGATTI gives you outdoor durability with precise temperature control. One of these will fit your home, your budget, and your hot‑water habits.

Here’s a quick comparison of the key specs that matter most.

Features	Camco Stand	ThermoMate CZ422NG	APUS 190k BTU	Rinnai RX199iN	FOGATTI Outdoor
Type	Stand for tank heaters	Tankless, indoor	Tankless, outdoor	Tankless, indoor/outdoor	Tankless, outdoor
Max Flow Rate	N/A (accessory)	5 GPM	8.1 GPM	11.1 GPM	8.1 GPM
BTU	N/A	113,000	190,000	199,000	180,000
Efficiency (UEF)	N/A	0.81	Not stated	0.98	Not stated
Best Use Case	Code compliance for 50‑gal tanks	Smaller homes, 1‑2 showers	Whole house, 3+ showers	Largest homes, 7 fixtures	Outdoor install, 3‑5 outlets

Camco Gas Heater Stand

The one you buy to pass inspection and keep your tank off the floor.

The Camco 11231 is not a water heater. It’s a heavy‑duty galvanized steel stand that lifts your residential gas water heater 18 inches above the floor. That height is required by National Fuel Gas and Plumbing Codes – it allows combustion air to reach the burner and prevents gas from pooling in case of a leak. If you’re installing a new 50‑gallon tank heater (or replacing an old one), this stand solves a real problem: code compliance without building a custom platform.

What stands out is how simple it is. The stand is made from 18‑gauge galvanized sheet metal, so it won’t rust or sag under a full 50‑gallon tank. It measures 21 by 21 inches, which fits heaters up to 22 inches in diameter. Assembly takes maybe 20 minutes with a screwdriver – no special tools. For homeowners replacing a tank heater that previously sat directly on concrete, this is the quickest way to meet code.

The trade‑off is obvious: it only works with tank heaters, not tankless units. And it’s limited to 50‑gallon tanks (or smaller). If you have a 75‑gallon or larger heater, this won’t fit. Also, the stand itself adds a bit of height, so make sure your water heater connections and gas line reach – you may need flexible connectors. Some buyers wish the stand had adjustable legs for uneven floors, but it’s a fixed design.

• Fits gas water heaters up to 22 inches diameter and 50 gallons
• 18‑inch height meets National Fuel Gas and Plumbing Codes
• Constructed from 18‑gauge galvanized steel, rust‑resistant
• Minimal assembly required – basic tools only
• Weight capacity is rated for a full 50‑gallon tank with water

Best for: Homeowners replacing or installing a 50‑gallon gas tank heater who need a quick, code‑approved stand without building one themselves.

ThermoMate CZ422NG Tankless

The smart choice for small to medium homes on a budget.

The ThermoMate CZ422NG delivers up to 5 GPM and 113,000 BTU, enough to run two showers at the same time. It’s an indoor unit designed for whole‑house use in homes with moderate hot‑water demand. If you live alone, as a couple, or with one kid, this unit will handle morning and evening routines without running out. The 0.81 UEF rating means you’ll save roughly 30% in gas costs compared to an old tank heater.

What really sets this model apart is its temperature stability. The internal chip adjusts heating 20,000 times per second, keeping the water within ±1°F of your set temperature. No more sudden cold blasts when someone flushes a toilet. The 3.5‑inch LED display shows flow, fan, and flame status, and error codes help you troubleshoot without calling a plumber. Frost protection kicks in automatically when temps hit 41°F, so it’s safe in unheated basements.

It’s not perfect for larger homes. At 5 GPM, running three showers at once will leave the third one struggling to stay warm (especially in winter with cold incoming water). The unit needs a 3‑inch vent and a 120V outlet, so retrofitting in an older home might require new venting. Also, the oxygen‑free copper heat exchanger is efficient but can be damaged by aggressive water chemistry – a whole‑house water softener is recommended if you have hard water.

• Max 5 GPM flow rate, 113,000 BTU input
• 98% thermal efficiency with oxygen‑free copper heat exchanger
• Temperature range 90–140°F, adjustable via LED display
• Includes freeze protection, boil‑dry, and overheat safeguards
• Compact: 21″H × 13″W × 7″D, standard ¾″ NPT water connections

Best for: Budget‑conscious homeowners with 1–2 bathrooms who want instant hot water and don’t need maximum flow for heavy simultaneous use.

APUS 190,000 BTU Outdoor

The one that works even when your water pressure is lousy.

The APUS outdoor unit pushes 190,000 BTU and 8.1 GPM, easily covering 3 showers plus 2 faucets at the same time. It’s designed for whole‑house demand, and its ultra‑low 0.79 GPM minimum flow rate means it fires up even with weak well water pressure or low‑flow fixtures. That’s a huge advantage for rural homes or anyone with a pressure regulator that throttles flow.

Smart controls are the headline here. You can adjust temperature (95°F to 149°F) via a wired remote or through the Tuya app on your phone. The ±1°F accuracy holds steady regardless of outside temperature. The outdoor‑rated body handles wind up to level 10 with electric anti‑freeze protection, so it’s fine in snowy climates. The 100% oxygen‑free copper heat exchanger with staged combustion cuts energy use by about 20% compared to a standard tank heater.

The downsize: installation is strictly outdoor. You cannot install this unit indoors without major venting modifications. The 120V cord is short, so you’ll need a nearby outlet. And while the app is convenient, some users report that the Wi‑Fi connection drops occasionally – the wired controller works every time. It also lacks a condensing mode, so efficiency numbers aren’t published (but staged combustion helps).

• 190,000 BTU, 8.1 GPM max flow rate
• Wi‑Fi app control (Tuya) plus wired remote included
• Wind‑resistant construction (rated for 10‑level winds)
• Minimum flow of 0.79 GPM – works with low water pressure
• Dimensions: 22.48″ × 15.51″ × 6.54″

Best for: Homes with low water pressure or a need for outdoor installation, where app control and reliable low‑flow activation matter more than ultra‑high efficiency ratings.

Rinnai RX199iN Condensing

The premium workhorse that fits indoors or outdoors.

The Rinnai RX199iN is a condensing tankless water heater with a staggering 199,000 BTU and 11.1 GPM. That’s enough for 7 fixtures at once – think 3 showers, a dishwasher, a washing machine, and a sink running simultaneously. It’s the only model in this list that can be installed indoors or outdoors thanks to Rinnai’s Versa Vent system (you just add the RX‑OVC vent cap for outdoor use). The UEF of 0.98 means nearly every BTU goes into heating water, not escaping up the flue.

What makes this a standout is its flexibility and smart features. The Smart Sense gas control adjusts automatically if you switch from natural gas to propane (or vice versa) – no conversion kit needed. The interface is simple, and the Quick Flush feature makes routine descaling much easier than on other units. You can add the Controlr module for Wi‑Fi control, but it’s sold separately. Rinnai requires professional installation, which is a good thing – this unit is powerful and complex.

The biggest trade‑off is the cost. This is the most expensive unit here, both to buy and to install. Professional installation can run $800–$1,500 depending on venting and gas line upgrades. It also requires a larger gas supply line (likely ¾″ or 1″), so older homes may need to upgrade. The unit itself is only the size of a small suitcase, but the installation footprint is bigger due to venting clearances. Finally, you’ll need the separate Controlr if you want app control – it doesn’t have built‑in Wi‑Fi.

• 199,000 BTU, 11.1 GPM max flow
• UEF of 0.98 – condensing, ultra‑efficient
• Indoor or outdoor install with Versa Vent system
• Smart Sense automatically adapts to natural gas or propane
• Quick Flush feature for simplified maintenance

Best for: Large families or multi‑bathroom homes where endless hot water and maximum energy savings justify a higher upfront investment and professional installation.

FOGATTI Outdoor Tankless

The rugged outdoor unit with four‑stage combustion for consistent temps.

FOGATTI’s 180,000 BTU outdoor tankless heater delivers 8.1 GPM, supporting 3–5 outlets at once. It’s built to live outside year‑round, with a bottom‑mounted fan that prevents smoke backflow and keeps the burner stable in windy conditions. The real trick is its four‑stage combustion system paired with water servo technology – it adjusts gas and water flow together to maintain temperature within ±1°F even when the weather swings from hot to freezing.

Durability is a strong point. The heat exchanger uses oxygen‑free copper (better corrosion resistance than stainless steel), and the burner is 304 stainless steel. CSA certification means it meets North American safety and performance standards. The compact size (26.2″ × 17.1″ × 7.1″) makes it easy to mount on an exterior wall, and the remote control panel lets you adjust settings from inside your home without going outside.

No unit is perfect. At 8.1 GPM, it’s a step below the Rinnai in raw capacity – you may notice a temp dip if you run 4 or 5 high‑flow showers at once. The efficiency numbers aren’t explicitly stated (no UEF rating given), so you’re trusting the 30% savings claim versus traditional heaters. The remote control is wired, not wireless, which means you need to run a cable through the wall. Some installers find the gas inlet placement slightly awkward for tight spaces.

• 180,000 BTU, 8.1 GPM max flow
• Four‑stage combustion system with water servo for ±1°F accuracy
• Oxygen‑free copper heat exchanger, 304 stainless steel burner
• CSA certified, bottom‑mounted fan for wind resistance
• Includes wired remote control for indoor temperature adjustment

Best for: Homeowners who want a durable, outdoor‑rated tankless heater with precise temperature control and don’t need the absolute highest flow rate offered by premium models.

How We Chose These Products

We started with the core problem: finding a natural gas water heater that delivers consistent hot water without wasting energy. That meant looking beyond brand names and marketing claims. We evaluated each product on flow rate, efficiency, installation requirements, and real‑world reliability based on specifications and common use cases.

The Camco stand earned a spot because it solves a real code issue that many DIY installers overlook. For tankless units, we focused on models that offer something distinct – the ThermoMate’s low‑temperature stability, the APUS’s low‑flow capability, the Rinnai’s flexibility, and the FOGATTI’s outdoor durability. We avoided units with generic specs that don’t stand out in any practical way.

Buying Guide: What Really Matters

Flow rate is the first number to check. For a family of four, aim for at least 6 GPM. A 1.5‑GPM shower head × 2 plus a kitchen sink at 1.0 GPM equals 4 GPM – so 6 GPM gives you a comfortable buffer. If you have two bathrooms with rain shower heads (2.5 GPM each), you’ll need 8 GPM or more. BTU output roughly tracks with flow: 180,000–200,000 BTU is standard for whole‑house units.

Efficiency matters more than you think. A condensing unit with a UEF of 0.95 or higher reuses exhaust heat to preheat incoming water, cutting gas consumption by 10–15% compared to a non‑condensing model. The Rinnai at 0.98 is the clear winner here. Also consider the minimum flow rate – if you have low water pressure, look for units that fire at 0.7 GPM or less (like the APUS). Otherwise the heater may cycle on and off at low flow.

Installation location dictates your options. Indoor units need proper venting (often 3‑inch PVC for condensing models). Outdoor units must be rated for wind and freezing temperatures. The Rinnai is the only one that works both ways. Finally, check gas line size – high‑BTU units require a ¾″ or 1″ gas pipe. If your home has ½″ pipe, you’ll need an upgrade or a lower‑BTU unit.

Our Top Recommendation

If we had to pick one, the Rinnai RX199iN is the best overall natural gas tankless water heater in this lineup. Its 11.1 GPM flow handles the largest households, the 0.98 UEF saves the most money over time, and the ability to install indoors or outdoors gives you unmatched flexibility. Yes, it costs more up front and requires professional installation, but you get years of reliable, efficient hot water.

For budget‑minded buyers, the ThermoMate CZ422NG is a strong runner‑up. It’s smaller, cheaper, and still delivers ±1°F accuracy. Pair it with a water softener if your water is hard, and it will serve a small family well. If you need outdoor installation and low‑flow operation, the APUS 190,000 BTU model is the smart pick. And for anyone replacing a 50‑gallon tank, don’t forget the Camco stand – it’s a small investment that keeps your installation code‑compliant and safe.

Frequently Asked Questions

Do I need a stand for a tankless water heater?

No. Tankless water heaters are wall‑mounted – they don’t sit on the floor. The Camco stand is only for traditional tank‑style water heaters that need to be raised 18 inches off the ground to meet gas code. If you’re going tankless, skip the stand.

Can I install an outdoor water heater in an unheated garage?

It depends on the model. Most outdoor units are designed for outside air and won’t operate correctly in a garage that doesn’t meet combustion air requirements. Some indoor units can be installed in a garage if they have sealed combustion and freeze protection. The Rinnai RX199iN can be installed indoors or outdoors, but check local codes – many garages require a specific venting setup.

How often should I descale a tankless water heater?

Once a year for homes with average water hardness (7–10 grains per gallon). If your water is very hard (over 15 grains), descale every 6 months. A vinegar and water solution run through the service valves does the job. The Rinnai’s Quick Flush feature makes this easier by providing a dedicated connection for the circulating pump.

Will a tankless water heater work during a power outage?

No. All the tankless units listed here require 120V AC power to run the fan, control board, and ignition. If the power goes out, you lose hot water – unlike a gas tank heater that can still supply gravity‑fed hot water (though without forced draft, some older models won’t light). Battery backup systems exist, but none of these units have one built in.