Our readers keep the lights on and my morning glass full of iced black tea. As an Amazon Associate, I earn from qualifying purchases.11 Best 40 Gallon Propane Water Heater | Best Gas Water Heaters

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The FOGATTI 170S delivers a commanding 170,000 BTU output paired with a 7.5 GPM flow rate, making it a strong candidate for a whole-home replacement of a traditional 40-gallon propane water heater. Its four-stage combustion system and advanced water servo technology maintain temperature within ±1°F, even when three to five fixtures are running simultaneously. This unit is engineered for indoor installation and draws from a standard 120V AC outlet for its electronic controls and ignition system.

Build quality centers on a high-efficiency copper heat exchanger and a 304 stainless steel burner, backed by a 5-year warranty on the heat exchanger and 2 years of full unit coverage. The compact footprint (25 x 16.3 x 7.3 inches) mounts directly to a wall, freeing up the floor space that a 40-gallon tank would occupy. The included remote control allows temperature adjustment from inside the home, and the unit is CSA certified for safety compliance.

User reports consistently highlight the immediate hot water delivery and stable temperature control, with many noting a seamless transition from a tank-style heater. The installation manual could be more detailed, particularly regarding gas line sizing and required pressure regulator specs, but once properly set up, the heater performs reliably across multiple seasons without the standby heat loss inherent to tank systems.

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Westinghouse brings its engineering reputation to this outdoor-rated propane tankless water heater, which pushes 180,000 BTU and 8.1 GPM to support 3–5 fixtures. The key advantage here is the outdoor design: it vents directly to the atmosphere, eliminates the need for a vent pipe through the roof, and frees up all indoor floor space that a 40-gallon tank would consume. Self-modulating technology adjusts the gas valve and water flow every few seconds to maintain ±1°F temperature stability, reducing the cold-burst problem common in older on-demand units.

Included with the heater is an indoor remote control panel with a clear LED display, so you can adjust the water temperature from inside your home without walking outside in cold weather. The unit also features integrated freeze protection—critical for outdoor propane installations in regions where overnight temperatures drop—and a variable-speed combustion fan that compensates for wind gusts. The compact wall-mount design weighs in without the bulk of a tank, and connections use standard 3/4-inch NPT fittings for straightforward plumbing tie-ins.

Buyers report that the Westinghouse delivers stable hot water across multiple simultaneous draws—two showers plus a dishwasher run simultaneously without noticeable pressure loss. Some note that the unit requires a 120V power source for its electronics, and in temperatures below 5°F, draining the system is recommended if the heater won’t be used for an extended period. The remote control convenience and easy gas conversion setup (from natural gas to propane via internal adjustment) make this a versatile pick for outdoor installs.

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The MIZUDO 180K competes directly with the Westinghouse outdoor line, delivering identical 180,000 BTU and 8.1 GPM specifications, but at a more accessible price point that appeals to buyers looking to replace a 40-gallon tank without a premium budget. It carries CSA certification and integrates overheat protection, accidental flameout protection, and IPX4 waterproofing, which means it can withstand rain and wind exposure when mounted on an exterior wall. The unit’s wind pressure resistance rating of 380PA helps maintain stable burner operation in gusty conditions.

Precise temperature control within ±1°F is achieved through an internal movement sensor that adjusts gas flow in real time as water inlet temperature changes. The heater measures 26.2 x 17.1 x 7.3 inches and uses standard 3/4-inch NPT connections, making it a straightforward swap for an existing outdoor tankless setup. Like most outdoor models, it requires a 120V AC power connection to run the control board and fan, and the included remote panel allows indoor temperature adjustment up to 32 feet away.

Customer feedback highlights the quiet operation and rapid heat-up time—users report hot water reaching the shower in about 35–40 seconds through existing plumbing lines. Some installations required additional fittings because the gas inlet is not a standard 1/2-inch MIP, so checking your existing gas line configuration beforehand is wise. The MIZUDO strikes a strong balance between peak performance and cost, making it a compelling choice for homes that need 8+ GPM throughput without paying a premium brand markup.

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The CAMPLUX WA686M steps up the output with 199,000 BTU and a peak flow rate of 8.4 GPM, making it one of the most powerful entries for homes that would otherwise rely on a 40-gallon propane tank. This outdoor-rated unit supplies 95°F–167°F water to 4–8 fixtures simultaneously, easily covering a whole home with multiple bathrooms, a kitchen, and laundry appliances. The weather-resistant design includes an oxygen-free copper heat exchanger rated at 84% efficiency, and the sealed combustion chamber uses intelligent 3-stage gas adjustment (18-12-8 fire rows) to optimize heat transfer during partial-load operation.

Temperature stability is a strong suit here: the unit incorporates a smart chip that performs thousands of calculations per second, combined with a high-precision gas proportional valve to hold fluctuations within ±0.5°F—tighter than the ±1°F standard common in this class. The heater lights reliably at a very low water pressure threshold of 0.02 MPa (about 2.9 PSI), which is a genuine advantage for off-grid or well-water properties. A 32.8-foot wired remote is included for indoor temperature control, and the installation kit supplies a brass T&P valve, high-temperature sealant, and mounting hardware.

Owners consistently praise the CAMPLUX for maintaining steady temperature even during back-to-back showers and report that customer service is responsive—several noted a warranty replacement handled without hassle after a freeze event. The unit requires a 120V power source and outdoor mounting with clearance for airflow, but the payback in continuous hot water availability and reduced propane consumption versus a tank heater is significant. If you have a high-demand household and want maximum flow from an outdoor install, this model delivers.

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The Rheem RTG-95DVLP-3 pushes the boundaries of what a residential propane tankless heater can do, delivering a massive 199,900 BTU and 9.5 GPM. That flow rate is enough to comfortably serve a 2–3 bathroom home with simultaneous high-demand activities—think two long showers, the dishwasher, and a load of laundry all at once without any temperature fade. Rheem’s hot-start programming prevents the cold water burst that plagued early tankless designs, so you won’t feel a temperature jolt when someone turns on a faucet in the middle of a shower.

Designed for indoor installation, the unit fits inside a compact 13.5-inch wide metal cabinet and mounts directly to the wall, reclaiming the floor space a 40-gallon tank would occupy. It requires standard 3/4-inch NPT water connections and proper venting through the wall or roof. The warranty is one of the strongest in the category: 15 years on the heat exchanger, 5 years on parts, and 1 year on labor, which reflects Rheem’s confidence in the build quality. Users report that the unit is noticeably louder than some competitors during operation—comparable to a lower-end dishwasher—but the raw output capacity compensates for the noise in high-demand scenarios.

Installation feedback indicates that the unit works well at elevations up to 8,000 feet with proper derating, and the propane conversion (if you start with a natural gas model) is straightforward. The primary requirement is a sufficiently sized propane tank and regulator system: the 199,900 BTU draw needs a large house regulator, not a standard BBQ regulator, to avoid starvation and pressure drops. For homes with serious hot water demands and a willingness to invest in proper gas infrastructure, the Rheem RTG-95 delivers unmatched flow among non-condensing indoor units.

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Rinnai’s RX199iN is the flagship condensing tankless water heater, combining a 199,000 BTU input with an 11.1 GPM output and a UEF rating of 0.98—that means 98% of the fuel’s energy goes into heating water, with almost nothing wasted up the vent. This efficiency level directly reduces propane consumption compared to any non-condensing or tank-style unit, making it the smartest long-term investment for off-grid homes or properties where propane delivery costs are a recurring expense. The condensing design uses small-diameter PVC venting, which simplifies indoor installation and keeps heat inside the system rather than exhausting it outside.

One of the RX199iN’s standout features is its Versa Vent and Smart Sense gas control system, which allows the same unit to be installed indoors or outdoors and switch between propane and natural gas through an onboard settings menu—no physical conversion kit required. The Quick Flush feature simplifies annual maintenance by automating the descaling process, and the unit supports the Rinnai Controlr module for WiFi-based temperature scheduling and system monitoring. At 30.1 x 18.5 x 11.4 inches and 55 pounds, the unit is slightly larger than non-condensing alternatives but still wall-mountable and space-efficient compared to a 40-gallon tank.

Owners report that the RX199iN handles simultaneous hot water draws across five to seven fixtures without any perceivable temperature or pressure drop, which is critical for large families. The condensing design does add complexity and cost upfront, but the fuel savings and extended lifespan offset this over time. Some users note that the WiFi module is sold separately and that the remote app integration can be improved, but the core heating performance is exceptional. For buyers who want the highest efficiency and flow rate available in a residential propane tankless heater, the Rinnai RX199iN is the gold standard.

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The Westinghouse Smart Indoor model brings WiFi app control to the tankless propane water heater category, allowing you to adjust water temperature, monitor operating status, and set schedules from your smartphone. Behind the smart features sits a solid 180,000 BTU heat engine that delivers 7.9 GPM—enough to support 3–5 fixtures simultaneously in a typical home. The self-modulating technology adjusts gas flow in real time to hold water temperature within ±1°F, reducing the cold burst issue common with non-modulating units.

The unit is CSA certified and designed for indoor installation with standard 3/4-inch NPT water connections. Freeze protection and a variable-speed combustion fan are built in, and the copper heat exchanger is designed for long-term durability. The wall-mount design is compact at 26.2 x 17.1 x 7.3 inches, freeing up the floor footprint a 40-gallon tank would consume. An LED display panel on the unit provides at-a-glance temperature and status information, supplementing the smartphone control interface.

Buyers appreciate the straightforward installation process and the convenience of adjusting temperature from a phone rather than walking to a mechanical panel. Some note that the smart features require a consistent WiFi connection and that the companion app could benefit from additional functionality like usage tracking or leak alerts. For homeowners who value remote control and the convenience of scheduling, the Westinghouse Smart Indoor offers a compelling package that marries solid heating performance with modern connectivity.

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The Rheem RTG-70DVLP-3 serves as a balanced entry point for households replacing a 40-gallon propane tank with a tankless system. Its 160,000 BTU output and 7.0 GPM rating are sufficient for 2–3 bathroom homes where two showers and a kitchen load might run simultaneously, though it won’t handle the peak demand of a six-person family with multiple full baths. The non-condensing design is simpler and more serviceable than condensing units, and the compact cabinet (13.5 x 24.2 x 10.3 inches) fits in tighter indoor spaces where a tank would crowd the area.

Rheem’s hot-start programming is included to prevent the cold water sandwich effect, and the unit supports a standard 3/4-inch NPT connection to water and gas lines. The setup had some reliability criticisms in the review data, with a few owners reporting issues with cold spots and noise levels, but also many positive reports of straightforward DIY installation and consistent long-term performance. The key to success with this unit is ensuring the propane supply system is properly sized: the 160,000 BTU rating requires a 3/4-inch line and a house-grade regulator, not a small BBQ-style regulator, to maintain pressure during high-demand draws.

Several experienced DIY installers have reported that this Rheem model is easier to install than expected, especially when paired with the optional Rheem vent kit and a proper pressure relief valve. User reports indicate that a 100-pound propane tank lasts about one month for a family of two adults and four children when moderate hot water usage is maintained. While the value proposition is strong, the mixed reliability feedback suggests that buyers should verify the unit’s compatibility with their specific gas setup and consider a professional installation to avoid common pitfalls.

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The Rinnai RX130iN brings the condensing efficiency advantage (UEF 0.97) to a lower BTU output tier, making it an excellent choice for smaller homes, cabins, or properties where the propane supply is more limited. At 130,000 BTU and 7.1 GPM, it still outruns a 40-gallon tank’s recovery rate while using significantly less fuel per gallon of hot water produced. Like its larger sibling the RX199iN, this unit can be installed indoors or outdoors using the Versa Vent system and switches between propane and natural gas via the internal Smart Sense menu without any hardware changes.

The condensing design extracts extra heat from exhaust gases, allowing it to use smaller PVC venting and place heat where it matters—in your water lines. This also means the unit can safely operate in tighter indoor spaces with less clearance than non-condensing alternatives. The Quick Flush feature reduces the effort required for annual descaling, a maintenance step that extends heat exchanger life in hard water areas. An easy-to-use interface panel on the unit allows degree-by-degree temperature adjustment, and the Controlr module (sold separately) adds WiFi connectivity for remote scheduling and monitoring.

Users in cold alpine climates report excellent performance, with the unit maintaining stable output even when groundwater temperatures are near freezing and outdoor temperatures hit 10°F. Some feedback notes that the unit is slower to reach full temperature than a larger BTU model, but once at setpoint, the hot water is consistent and endless. The Rinnai brand reputation for reliability and the strong 5-year parts and labor warranty add confidence for buyers who plan to keep the heater for the long haul. This unit is the sweet spot for efficiency-focused buyers who don’t need the absolute highest flow rate but want to minimize propane consumption from day one.

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The FOGATTI Comfort 120S is a more modest unit aimed at small homes, cabins, or vacation properties where maximum flow isn’t necessary. Its 120,000 BTU output and 5.1 GPM rating can support 2–4 fixtures simultaneously—think one shower and a kitchen sink, or two showers with careful timing. This is a direct replacement for a 40-gallon propane tank in scenarios where the demand is moderate and energy efficiency and space savings are the primary goals. The outdoor installation model vents freely and avoids the need for a chimney or metal vent pipe.

Precision temperature control is still a priority here, with water servo technology and four-stage combustion maintaining temperature within ±1°F. The 304 stainless steel burner and high-efficiency copper heat exchanger are built to last, backed by a 2-year full unit warranty and 5 years on the heat exchanger. Installation is straightforward with 3/4-inch NPT connections, and the compact size (26.2 x 17.1 x 7.1 inches) allows mounting in tight outdoor spaces. The included remote control panel lets you adjust temperature from inside the home.

User reviews highlight the immediate on-demand operation—hot water arrives quickly after turning on a faucet—and the ability to run a shower and kitchen sink simultaneously without a noticeable drop in pressure or temperature. Some mention that the installation instructions could be clearer, especially regarding gas line sizing and pressure regulator requirements, but the manufacturer’s support team is responsive. For budget-conscious buyers or those with smaller hot water needs, the FOGATTI 120S provides an efficient and reliable path away from the 40-gallon tank paradigm without over-investing in capacity you won’t use.

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The CAMPLUX WA528 is the most accessible entry point for anyone wanting to replace a 40-gallon propane water heater with a tankless unit without a large budget allocation. It delivers 150,000 BTU and a maximum flow rate of 6.4 GPM, which is sufficient for 3–5 water points—three bathrooms, plus a kitchen and an outdoor spigot. The WA528 is CSA certified with anti-freeze, overheat, and dry-fire protections, plus flame failure detection as a standard safety suite. The outdoor installation design eliminates the need for indoor venting, and the compact dimensions (23.4 x 14.9 x 6.7 inches) make it one of the smallest units in this comparison.

Temperature control is handled by advanced water flow sensors and a smart chip that adjusts the high-precision gas proportional valve, holding water temperature within ±1°F. The unit uses standard 3/4-inch NPT fittings for both water and gas connections, and the included components bundle a gas shut-off valve and a wired remote control for indoor temperature adjustment. At 31.3 pounds, the WA528 is light enough that two people can easily mount it on an exterior wall using the supplied hardware.

Owner experiences are generally very positive, with many noting the fast response time and stable temperature output even at low water pressure (down to 24 PSI reported by one user). The company’s customer service also receives high marks—several reviews mention prompt replacements under warranty after freeze damage. Some users note that the remote control is basic and that the unit doesn’t include a pressure relief valve in the box, so you’ll need to purchase one separately for a proper installation. For the price, the WA528 offers a remarkably strong feature set and reliable performance for budget-minded buyers looking to transition away from a tank-based system.