Indoor Installation Tankless Hot Water Heaters Compared: Cover Gas and Propane Options for Indoor Use

Our Verdict and How We Chose

The FOGATTI Tankless Propane Water Heater is the best Tankless Hot Water Heater for Indoor installation because it provides 4.0 GPM of flow with a 90,000 BTU heating power.

Choosing a tankless water heater often leads to analysis paralysis when trying to balance BTU requirements against available indoor space. Selecting the wrong unit can result in a flow rate shortfall, leaving you with cold water mid-shower when other fixtures are running.

The FOGATTI Tankless Propane Water Heater solves this by offering a reliable 4.0 GPM output for propane users. If you require a higher flow rate of 7.5 GPM, the FOGATTI Natural Gas Tankless Water Heater is a better fit, while the Rinnai RUR160iN Condensing Tankless Hot Water Heater serves those seeking a premium 9 GPM output with a built-in recirculation pump.

At Green Writer we evaluated the tankless water heater installation options we track against this topic’s criteria. The selected models cover a price range from $256.49 to $1298.43, with a median price of $1298.43 across our comparison.

Full Comparison Table

Prices are approximate and move frequently – check the current price before deciding. “Not stated” means the manufacturer listing does not give that figure – we do not estimate it.

The FOGATTI Natural Gas Tankless Water Heater offers the strongest price-to-spec ratio because it provides 7.5 GPM flow at a $289.99 price point.

The Picks Reviewed in Detail

The 3 picks below run from $256.49 to $1298.43, reviewed in rank order.

FOGATTI Tankless Propane Water Heater

The FOGATTI Tankless Propane Water Heater made this list as a versatile mid-range option for users requiring a propane-fueled indoor solution. It balances a 90,000 BTU heating power with a 4.0 GPM flow rate, providing consistent performance for 2-3 simultaneous locations.

What we like: This unit features a copper heat exchanger and a micro-flame design with negative pressure. The chip-based temperature control adjusts power 1,000 times per second to maintain a variance within 2F. It also includes a 5-year warranty on the heat exchanger.

Keep in mind: With a 4.0 GPM flow rate, this model may struggle to provide a steady stream if you run multiple high-flow fixtures at once. It is best suited for smaller households or those with lower simultaneous demand.

Rinnai RUR160iN Condensing Tankless Hot Water Heater

The Rinnai RUR160iN Condensing Tankless Hot Water Heater is our high-performance pick for those seeking maximum flow and advanced features. It offers a high 9 GPM flow rate and utilizes condensing technology for increased efficiency.

What we like: The RUR160iN includes a built-in recirculation pump and ThermaCirc360 technology to maintain hot water availability. It features a 15-year residential warranty on the heat exchanger and supports Wi-Fi monitoring for remote status checks.

Keep in mind: This is a premium, discontinued model, and you should verify the availability of the RSC160iN replacement. The higher price point makes it a significant investment compared to standard gas units.

FOGATTI Natural Gas Tankless Water Heater

The FOGATTI Natural Gas Tankless Water Heater is selected for its high-output heating power and rapid response times. It provides a 170,000 BTU heating power, making it a robust choice for natural gas environments.

What we like: This unit provides a 7.5 GPM flow rate and maintains temperature control within 1F. It is compact, occupying only one-third of the space of a traditional tank heater, and is compatible with standard 3/4″ NPT water inlet fittings.

Keep in mind: While it offers a high flow rate, the 170,000 BTU output may be a limitation in extremely cold climates where higher demand is required. It is best for standard residential indoor use.

How many gallons per minute (GPM) do I actually need for my household?

The GPM you need depends on how many fixtures you run at once. A flow rate of 3.5 GPM is the minimum for a standard shower head, while 1.2 GPM is the standard for high-efficiency models. If you need to run two showers and a sink simultaneously, you should look for a unit capable of 10 GPM. The Rinnai RUR160iN meets this high-demand threshold at 9 GPM, while the FOGATTI Natural Gas model provides 7.5 GPM for moderate simultaneous use.

How much clearance do I need around the unit for local building codes?

Clearance requirements for the FOGATTI and Rinnai units depend on local building codes and specific venting requirements. Because these units use 3-inch OD venting or specific gas connections, you must confirm the required clearance with a qualified installer before purchasing. Check your local regulations for specific “clear to combustible” distances and service access requirements for your specific installation site.

The Specs That Decide This Purchase

Fuel Compatibility

Fuel compatibility depends entirely on your existing gas lines, as you must choose between natural gas and propane systems. The FOGATTI Natural Gas Tankless Water Heater is designed specifically for natural gas lines, while the FOGATTI Tankless Propane Water Heater provides a dedicated solution for propane setups. Before ordering, confirm your home’s fuel source, as these systems are not interchangeable and require specific burner designs to function safely.

Maximum Flow Rate

Maximum flow rate determines how many fixtures you can run simultaneously without a drop in temperature. A 3.5 GPM flow rate is the minimum for a standard shower head, but the Rinnai RUR160iN offers a much higher 9 GPM flow rate for high-demand households. The FOGATTI Natural Gas Tankless Water Heater provides a mid-range 7.5 GPM, while the FOGATTI Tankless Propane Water Heater provides 4.0 GPM. If you need to run two showers and a sink at once, you should prioritize units that exceed the 10 GPM threshold or offer high-output BTU ratings like the 170,000 BTU found in the natural gas model.

Condensing Efficiency

Condensing efficiency determines both your energy savings and your venting requirements. Condensing models, like the Rinnai RUR160iN, capture waste heat to increase efficiency, which can offset a higher upfront cost over time. Because it is a condensing unit, it may have different venting requirements than non-condensing models. Non-condensing units, such as the two FOGATTI models, are standard designs; you must verify with a professional installer whether your local building codes allow for standard venting or require specific stainless steel piping for your climate.

Indoor Clearance Requirements

Indoor clearance requirements depend on the physical dimensions of the unit and the specific venting needs of the model. The FOGATTI Natural Gas Tankless Water Heater measures 26.2″ x 17.1″ x 7.3″, occupying roughly one-third the space of a traditional tank. The FOGATTI Tankless Propane Water Heater is smaller at 22.76″ H x 14.57″ W x 7.0″ D. Because these are indoor installations, you must ensure your mounting area meets the manufacturer’s clearance and that a qualified installer can verify the required 3-inch OD venting or specific gas line connections before the unit is mounted.

What You Need vs What These Picks Deliver

Match the job you actually need done to what it requires, then check whether anything on this page reaches that level. Where nothing does, the row says so.

Thresholds are the levels this category is generally held to, not manufacturer claims. Check them against your own workload before buying.

Who Buys Tankless Water Heater Installations, and What It Really Costs

Buying Questions Answered

Do I need to upgrade my gas line or electrical panel for these models?

You must verify your existing gas line and electrical capacity with a qualified installer before purchasing, as specific requirements depend on your home’s infrastructure. The FOGATTI Natural Gas Tankless Water Heater requires a 170,000 BTU input, while the FOGATTI Tankless Propane Water Heater requires a 90,000 BTU input and a 120V AC power supply.

What is the average lifespan of these units compared to traditional tanks?

Tankless water heaters generally offer a longer service life than traditional tanks, which often require replacement every 10 to 12 years. The Rinnai RUR160iN Condensing Tankless Hot Water Heater includes a 15-year residential warranty on the heat exchanger to support long-term reliability.

Which model should I choose for high-volume flow?

If you need to support multiple fixtures simultaneously, the Rinnai RUR160iN Condensing Tankless Hot Water Heater is the strongest option due to its 9 GPM flow rate. This unit provides significantly more volume than the FOGATTI Natural Gas Tankless Water Heater, which provides 7.5 GPM.

Is the FOGATTI Tankless Propane Water Heater suitable for my space?

Yes, the FOGATTI Tankless Propane Water Heater has a compact footprint measuring 22.76 H x 14.57 W x 7.0 D. Its small size makes it a viable choice for indoor installations where space for a traditional tank is limited.

Before choosing a model, you should learn about different tankless water heater types to find your best fit.

Ensure your unit meets local codes by viewing required tankless water heater safety certifications.

Who Should Skip These Tankless Water Heater Installations

If you need to run two showers and a sink simultaneously, you require a 10 GPM flow rate. None of the options on this page reach that threshold, as the highest flow rate provided is 9 GPM. These units are suitable for standard residential needs but do not meet high-volume requirements.

For high-volume applications, you should look for multi-unit commercial systems or high-flow residential models. If you require a higher flow capacity than these models provide, see our guide on best tankless hot water heater for high flow (up to 11 GPM).