13 Best Condensing Tankless Water Heater | No More Cold Showers

Check Price on Amazon

The 11 GPM powerhouse that ends cold showers for a 3-bedroom home.

This is the unit that makes a 7-fixture household feel like it has an endless well of hot water. The RX199iN delivers 11 gpm, which the maker says covers 7 fixtures at once, and it does it with a super-high UEF of.98 — that is close to perfect efficiency for a gas appliance. Owners describe it as reliable and quiet, with one noting it has served a 3-bedroom home well for a full year.

On the flex side, this one model runs on either natural gas or propane thanks to the Smart Sense gas control, and it installs indoors or outdoors with the Versa Vent. At 55 pounds and 18.5″W x 30.11″H, it is a compact suitcase-sized box that frees up your garage floor. The reliability is the biggest draw — it is the #1 praised aspect, with heat generation close behind.

Installation honestly varies by situation. Some buyers found it easy; others describe it as a challenging project, so plan for a professional if you are not handy. The recurring gripe is the noise level, which some find noticeable, though most call it quiet. As buyers report, “Its been a year now so I can honestly say this water heater was worth every penny I paid for it.”

Check Price on Amazon

The smart-budget pick that still runs three showers at once.

If you want the efficiency of condensing without the premium price tag, the ThermoMate RTC68iN is the one to weigh. The dual heat exchange system (stainless steel plus oxygen-free copper) is what captures waste heat to hit that 0.91 UEF, which the maker says cuts annual hot water costs by about 17% versus traditional models.

This is a wall-mount indoor unit at 14.57″W x 28.44″H, making it one of the slimmer profiles here. The smart water mixing valve keeps temperature stable even during multi-shower use, and a sealed combustion design keeps it quiet. Owners praise the easy installation and steady hot water, with one calling it “perfect” for on-demand needs.

The honest catch is the hidden costs. Owners mention: “It doesn’t come with everything you need to hook it up and if you are going from a tank heater to tankless be ready to spend another for parts.” That covers gas shut-off valves, isolation valves, and a pressure relief valve. Also, as a condensing unit, it produces mildly acidic condensate that needs a drain and an external neutralizer kit (not included) to protect your pipes.

Check Price on Amazon

A straightforward 180,000 BTU workhorse that installs without drama.

For many homes, the Rheem 9 GPM is the ticket to endless hot water without overcomplicating things. It delivers 0.4 to 9 gpm of flow and fires up to 180,000 BTU, which is plenty for a mid-sized family running a couple of showers and the dishwasher. The temperature range runs 100 to 140°F, defaulting to a comfortable 120°F, and it includes an electric ignition — no standing pilot light to fuss over.

At 59.9 pounds and 17.7″W x 23.7″H, this is one of the heavier, more compact units here. The #1 praised aspect is installation — owners find it straightforward, with one saying it “installed and working perfectly” and another highlighting a polite delivery crew that placed the unit right where it was needed. The build quality is also praised, and it runs quietly and efficiently per the manual.

The warranty is solid: 15 years on the heat exchanger, 5 years on parts, and 1 year on labor. One owner advises adding an expansion tank and pressure regulator for constant pressure, and notes a gas smell in the exhaust (at 93% efficiency) — so keep the vent away from lounging areas. This is a dependable, no-surprises pick.

Check Price on Amazon

The same flexible Rinnai brains, sized for 6 fixtures at once.

The RX160iN is the slightly smaller sibling to our top pick, trading a little flow for a lower entry point — but cold-water wait while the heater fires up. It includes a built-in recirculation system, so hot water is already in the pipes when you turn on the tap. It delivers up to 11 gpm at 199,000 BTU, positioning it among the most powerful units here, with a.94 UEF efficiency rating.

Its Auto-Learn Programming tracks your water usage over time and auto-programs to meet hot water needs at peak times — a smart feature you do not see on most competitors. The compact, space-saving design is perfect for a tank replacement, and the water & gas leak detection will shut the unit down and give an error code for safety. Owners love the instant hot water and the ability to run multiple simultaneous showers.

The honesty here is that reliability gets harsh feedback. Multiple reviewers point out failures — a cracked heat exchanger, a plastic flame sensor window that burns, and warranty disputes leaving them without hot water for a month. One owner notes that while it works great initially, it quit after about a year. This is the one to buy with eyes open: the feature set is excellent, but the track record is the weakest of our picks.

Check Price on Amazon

A featherweight 38-pound heater that vents with cheap Schedule 40 PVC.

If you are replacing an aging 40-gallon tank in a smaller home, the Noritz NRC66DVNG is the efficient, light, and easy pick. At only 38 pounds and 13.8″W x 23.6″H, it is one of the lightest and most compact units on the list — easy for one person to lift and mount. It flows 6.6 gpm, which owners say handles multiple fixtures without issues in a typical home.

The big practical win is the venting. This condensing unit can be vented with Schedule 40 PVC pipe and fittings, which is dramatically cheaper and easier to source than stainless steel venting required by non-condensing units. It also earns points for low NOx emissions, a digital temperature control, and a quiet, small footprint. Shoppers say gas use dropping 10-20% after switching, and a 6-month update found the unit running flawlessly.

The common trade-off is the “cold-water sandwich” — a brief slug of cold water when the heater cycles — and the need for regular descaling and annual cartridge replacement to keep it happy. This is a great fit for a 2-3 person household that wants efficiency without the bulk.

Check Price on Amazon

The propane twin of our budget pick, tuned for off-grid and tank-based homes.

This is the liquid propane version of the Noritz NRC66, built for homes that run on LP tanks rather than natural gas lines. It delivers the same 6.6 gpm flow at 38 pounds and 14″W x 26″H, and it shares the same low NOx, high-efficiency condensing design and Schedule 40 PVC venting. Buyers report plenty of hot water even at the lowest setting, and it maintains good temperature when running two showers at once.

The standout praise is for the build quality — owners describe the Japanese attention to detail and recommend getting the matching valve made for this model. It holds a maximum temperature of 140°F, giving you a bit more headroom than some competitors. The included remote thermostat and 6-foot power cord add convenience.

Two honest cautions: this unit is strictly LP-only, so do not expect a natural gas conversion without spending extra. And for cold climates, the exhaust is acidic (do not reuse an old metal vent), and owners recommend a backflow preventer and even a 100W bulb near the coils to prevent freezing. The intake/exhaust routing instructions are also a bit confusing — keep the intake and exhaust 4 feet apart as directed.

Check Price on Amazon

The garage-wall classic with instant heat and a 15-year record.

The Takagi T-H3J-DV-N is the kind of heater that owners literally say “the last one lasted 15 years with a problem” — a track record that earns trust. It flows 6.6 gpm, attaches neatly to a garage wall, and satisfies the 2012 SCAQMD Rule 1146.2 for ultra-low NOx emissions, making it one of the cleaner-burning options for California buyers. The water is hot almost instantaneously, and the compact space-saving design frees up the floor entirely.

Owners praise the quality and the strong tech support from the vendor, with one noting the seller even helped secure a tax credit certificate. It uses computerized safety features and has no pilot light to worry about, simplifying maintenance. The unit needs little space and is rated for continuous on-demand use.

The honest notes: some owners found it heats slower than an old tank heater, so adjust expectations on “instant” heat. And if you plan to use it for radiant floor heating, know that it is not guaranteed for that duty — one owner had a gas valve fail three times over about 9 months. Also, be ready to upgrade your gas line (from 1/2″ to 1″) for proper flow. This is a solid, proven pick for standard whole-house use.

Check Price on Amazon

Built-in recirculation and marine-grade steel for 3-4 bath homes.

The AO Smith ATI-540P-N is built for the bigger home that has been burned by slow-hot-water waits before. It flows up to 10 gpm — enough for 3 to 4 bathrooms depending on your climate — and includes an integrated hot water recirculation pump, so the water is waiting for you when you step in. The 199,000 BTU burner handles heavy simultaneous demand, and the 0.93 UEF keeps the gas bill reasonable.

Durability is the sales pitch here: it uses marine-grade 316L stainless steel and commercial-grade materials, with safety features like an exhaust and water temperature safety control, an overheat cut-off fuse, and an air-fuel ratio sensor. Customers note it runs “excellent” for a condo, handling a shower and washer at the same time without pressure or temperature drops. The built-in scale prevention reduces mineral buildup, which means less descaling maintenance than a typical tankless.

The practical catch: it uses a single exhaust that is costlier than standard PVC, and your gas lines must be sized for 200K BTU max. One owner notes it is not recommended for midwestern regions, so check the ground-water temperature map before committing. Despite that, it is a well-regarded, easy-install unit for a condo or a 3-bath home with the budget for premium gear.

Check Price on Amazon

The 9 GPM Rinnai that is barely audible in a 1,100 sq ft house.

The Rinnai RU160iN is the ENERGY STAR-qualified workhorse for homes that want Rinnai dependability with a focus on quiet operation. It flows 9 gpm (up to 6 appliances at once) with a UEF of 0.97, and it comes with Circ-Logic — a feature that pairs with an external pump to reduce wait time via scheduled or on-demand recirculation. Owners consistently call it quiet, describing it as barely audible even in a small house, and note it starts within seconds of a tap opening.

The DIY-friendly install is a highlight, with several owners completing it themselves using PEX and re-piping. One owner measured 90 seconds to reach 110°F at the farthest shower (25-30 feet of pipe) — half the time of their old tank unit. The default 120°F temperature is easy to regulate, and it survives power outages without needing resets.

There are two recurring themes to know. First, some owners find the fan randomly hums when the unit is idle (a condensing byproduct). Second, there is a noticeable pressure drop for some, with one owner noting reduced flow to the shower and kitchen sink. The warranty is a bit lighter than modern Rinnai models: 120 months on the heat exchanger, 60 months parts, 12 months labor. It is a strong, proven unit for a 2-bath home.