The Rinnai I-Series Plus combi boilers are the clearest efficiency-focused options in this selection: both list a 96% AFUE rating and provide space heating and domestic hot water from one appliance. The 90,000 BTU model is best to evaluate for lower demand, while the 150,000 BTU model offers a higher stated heating capacity. The Noritz is another genuine combi option, but its listing does not provide an efficiency rating. Two remaining products are not combi boilers, so they are included only as clearly labeled alternatives—not as equivalent replacements.
| Product | Category | Notable listed information | Best suited to |
|---|---|---|---|
| Rinnai I-Series Plus 90k | Combi boiler | 96% AFUE; 90,000 BTU | Buyers assessing a lower-capacity combi |
| Rinnai I-Series Plus 150k | Combi boiler | 96% AFUE; 150,000 BTU | Buyers needing a higher-capacity option |
| Noritz NRCB180DV-NG | Combi boiler | Up to 9.8 GPM DHW; 100,000 BTU space heating | Buyers comparing stated hot-water flow and heating output |
| Rinnai I-Series Plus 90k Solo | Heating-only boiler | Up to 96% AFUE; natural gas or propane | Buyers who do not need a combi appliance |
| Taylor Swoden 1L kettle | Countertop electric kettle | 1-liter capacity; keep-warm function | Buyers seeking a small appliance for beverages |
Rinnai I-Series Plus 90k Combi Boiler
Best for: Homeowners comparing a lower-capacity combi boiler with a stated high efficiency rating. The listing identifies this as a 90,000 BTU condensing unit that supplies home heating and hot water in one appliance.
Its listed 96% AFUE rating makes it the strongest documented efficiency match among the combi products here. The Smart Sense Gas Valve is described as managing energy use and supporting heating and hot-water control. The listing says the unit is for natural gas or propane, but buyers should confirm fuel configuration and installation requirements with a qualified professional.
Why it was selected: It combines a stated AFUE figure, a defined capacity, and both functions central to a combi system. It is better to compare with the 150k model when sizing the appliance to a home’s heating load and hot-water demand.
Limitation: The listing does not give a domestic-hot-water flow rate or detailed sizing guidance. A 96% AFUE rating alone does not establish that this capacity will suit a particular home.
Rinnai I-Series Plus 150k Combi Boiler
Best for: Buyers whose heating-load assessment points toward the higher of the two listed Rinnai combi capacities. This model is identified as a 150,000 BTU appliance for space heating and domestic hot water.
Like the 90k version, it lists 96% AFUE and Smart Sense Gas Valve technology. That makes the two Rinnai models straightforward to compare on the efficiency figure provided: the stated rating is the same, while the listed BTU capacity differs. The appliance is described as supporting natural gas or propane; verify the exact model configuration before purchase.
Why it was selected: It offers the same documented efficiency rating as the smaller Rinnai while providing a higher stated capacity. Choose it only when a professional load calculation and household hot-water requirements support that capacity; a larger rating is not automatically more efficient in every installation.
Limitation: The supplied product information does not state a domestic-hot-water flow rate. The listing’s 96% AFUE should not be treated as a complete measure of seasonal performance in a particular home.
Noritz NRCB180DV-NG Combination Boiler
Best for: Buyers who want to compare a natural-gas combi boiler with specified domestic-hot-water flow and space-heating output. The listing states up to 9.8 GPM for domestic hot water and 100,000 BTU for space heating.
The Noritz is described as providing simultaneous domestic hot water and home heating, with superior temperature stability for hot water. It also has a built-in pump and is identified as an indoor direct-vent combination boiler, with standard-vent conversion noted in the product name. These details can help buyers compare functions and installation configuration with other combi models.
Why it was selected: It is a genuine combination-boiler option and provides output details that are not supplied for the Rinnai combi listings. Those figures may help a contractor assess fit against household demand.
Limitation: The supplied features do not state an AFUE or other efficiency percentage. Do not assume it is more or less efficient than the Rinnai models without checking current manufacturer documentation for the exact model.
Rinnai I-Series Plus 90k Solo Boiler
Best for: Buyers comparing a high-efficiency heating-only boiler, rather than a combi boiler. The listing describes up to 96% AFUE, Smart Sense Adaptive Gas Valve technology, Bluetooth capability, and compatibility with the Rinnai Central app.
The product is listed as supporting natural gas or propane and offering multiple installation options. Its 90,000 BTU rating can be considered during a heating-system comparison, but output suitability should be established from the home’s heat-loss calculation. This model may be relevant when a buyer wants space heating and does not require the boiler itself to provide domestic hot water.
Why it was selected: It offers a useful comparison point for the efficiency rating and smart-control features in the Rinnai line. It is not a substitute for a combi unit when integrated domestic hot water is required.
Limitation: This is a solo heat boiler, not a combination boiler. The listed information does not describe it as supplying domestic hot water.
Taylor Swoden 1L Electric Kettle
Best for: People seeking a small countertop appliance to heat water for tea or coffee. This is not a home-heating boiler or a combi boiler, so it should not be considered for central heating or household hot-water service.
The listing describes a 1-liter glass kettle with a removable stainless-steel tea infuser, a keep-warm setting, automatic shut-off, and boil-dry protection. It says the keep-warm function holds water between 176°F and 185°F. The product is designed for beverage preparation, not plumbing or heating-system integration.
Why it was selected: It appears among the supplied products and may match searches for a small water boiler, but its role is fundamentally different from that of a residential combi boiler. Its listed features are relevant only to countertop use.
Limitation: It cannot provide space heating or serve as a combi boiler. The listing’s efficiency comparison is specific to its kettle use and should not be compared with boiler AFUE.
Buying Guide: How to Choose an Efficient Combi Boiler
What does “efficient” mean for a combi boiler?
AFUE, or Annual Fuel Utilization Efficiency, is a measure of how effectively a fuel-burning heating appliance converts fuel into heat over a standardized period. Of the combi boilers in this selection, the two Rinnai models list 96% AFUE. The Noritz listing does not provide an AFUE figure, so the products cannot be ranked on a like-for-like efficiency basis from the supplied information alone.
Efficiency is only one part of ownership. Proper sizing, system setup, controls, maintenance, and the home’s heating needs affect real-world operation. Ask a qualified heating professional to confirm the model’s current specifications and whether the published rating applies to the exact configuration being considered.
How should you choose between 90,000 and 150,000 BTU?
Do not choose a boiler by square footage alone or assume that the larger capacity is a better option. A contractor should calculate the home’s heat loss and assess hot-water demand, including the number of fixtures likely to be used at once. The Rinnai 90k and 150k listings share the same stated 96% AFUE, but they differ in listed BTU capacity.
Ask for the heating output and domestic-hot-water performance for the exact model. The supplied Rinnai descriptions do not state hot-water flow rates, which limits direct comparison with the Noritz listing’s stated maximum of 9.8 GPM.
Which matters more: heating output or hot-water flow?
Both matter, but they answer different questions. Heating output relates to the boiler’s ability to meet the home’s space-heating load. Domestic-hot-water flow is relevant to the amount of hot water available at a given time. A household with overlapping showers or other hot-water uses should ask the installer to assess peak demand, not just the boiler’s heating capacity.
The Noritz listing provides both a domestic-hot-water flow figure and space-heating output. For the Rinnai combi products, the listed information provides BTU ratings and AFUE but not a hot-water flow figure. Request manufacturer documentation to compare these specifications accurately.
What fuel and venting details should you verify?
Confirm that the exact boiler configuration is available for the fuel used at the home. The Rinnai combi descriptions mention natural gas or propane, while the Noritz product name identifies a natural-gas model. Do not assume that changing the fuel is a simple adjustment; verify permitted configurations and installation instructions with the manufacturer and installer.
Venting and installation requirements also vary by model. The Noritz listing describes an indoor direct-vent unit and notes standard-vent conversion. Have a professional confirm that the proposed installation meets the model’s instructions and applicable local requirements.
Does a combi boiler make sense for every home?
A combi boiler combines space heating and domestic hot water in one appliance. That arrangement may suit buyers seeking one unit for both functions, but the right system depends on the home’s demand, layout, and existing equipment. A heating-only boiler, such as the Rinnai solo model listed above, is a different category and should not be selected when an integrated hot-water function is required.
Discuss peak hot-water use and the home’s heating load before deciding. If a household has unusually high simultaneous demand, ask the installer whether the chosen combi model can meet it or whether another system design should be considered.
Which controls and features are worth comparing?
The Rinnai combi listings mention Smart Sense Gas Valve technology for energy management. The Rinnai solo model lists Bluetooth capability and compatibility with the Rinnai Central app. These are distinct listed features; do not assume that a feature on the solo boiler is included on either combi model unless the exact model documentation confirms it.
Compare the controls you will actually use, along with installation needs and service access. Ask the contractor which control functions are supported on the exact appliance and whether additional equipment is required. Avoid basing a purchase decision on a feature name alone.
Frequently Asked Questions
Which listed combi boiler has the highest stated AFUE?
The Rinnai I-Series Plus 90k and 150k combi boilers each list 96% AFUE. The Noritz combi listing does not provide an AFUE figure, so the supplied information does not support an efficiency comparison for that model.
Is the Rinnai 150k combi boiler more efficient than the 90k model?
Both list the same 96% AFUE. The 150k model has a higher stated BTU capacity, but the provided information does not show that it is more efficient. A professional should determine the appropriate capacity for the home.
Does the Noritz NRCB180DV-NG provide domestic hot water?
Yes. Its listing describes simultaneous domestic hot water and home heating, with a maximum stated domestic-hot-water flow of 9.8 GPM.
Can the Rinnai 90k solo boiler replace a combi boiler?
Not as a direct equivalent based on the listed features. The Rinnai 90k solo model is described as a heating-only boiler, while a combi boiler combines space heating with domestic hot water.
Is the Taylor Swoden kettle a boiler for home heating?
No. It is a 1-liter electric kettle for heating beverage water. It is not designed to provide central heating or household hot water through plumbing.