Cleaning Products
June 15, 2021

7 Best Gas Boilers For Home Heating in 2021

We reviewed the best gas boilers for your home, so keep reading.

NOTE: We may earn money from links on this page, but we only recommend products we know will make your life easier.

Our Top 5 Picks

roman peysakhovich
About Your Guide

Roman Peysakhovich

CEO and educator at Onedesk. Roman has over 10 years of experience as a cleaning business owner. When not operating his cleaning business, he's researching and reviewing the household products to help consumers make the best purchase.

Why trust Onedesk?

Onedesk spends thousands of hours researching, analyzing, and reviewing products to recommend the best picks for most consumers. We work closely with experts to make sure every piece of content we publish is fact-checked and reviewed.

What is the best gas boiler for heating your home?

We asked ourselves the same question.

And now, we’re here to answer it.

Keep reading to find out which gas boilers are best for keeping your home heated properly.

We’ll also cover some boiler basics, how heat is distributed, and much more.

These are the best gas boilers in 2021. Before we get started, we recommend you watch this short video:

Now that you know how gas boilers work, let's dive right into the reviews.

Our Top 5 Picks (Comparison)
Rinnai i150SN Condensing Gas Boiler
  • Best Gas Boiler On The Market
  • Rinnai
Buy Now →
Noritz Indoor Direct Combination Boiler
  • Best Direct Combination Boiler
  • Noritz
Buy Now →
Rinnai Q-Series Condensing Boiler
  • Best Natural Gas Boiler
  • Rinnai
Buy Now →
Rheem Tankless Natural Gas Water Heater
  • Best Tankless Gas Boiler
  • Rheem
Buy Now →
Ecosmart Electric Tankless Water Heater
  • Best Affordable Gas Boiler
  • Ecosmart
Buy Now →

Rinnai i150SN Condensing Gas Boiler

Weight: 61.9 pounds

Dimensions: 10.9 x 18.5 x 26.4 inches


  • A heat-only model which offers the comfort of whole home heating
  • Designed to offer an outdoor reset for optimized home heating
  • 95% AFUE efficiency
  • Convenient control options
  • Not very heavy


  • It’s expensive

If you’re on the lookout for a heat-only gas boiler that will help you optimize your home heating, look no further than the Rinnai Condensing Gas Boiler.

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Noritz Indoor Direct Combination Boiler

Weight: 95 pounds

Dimensions: 12.8 x 18.5 x 27 inches


  • Easy to install
  • Less expensive than other boilers on this list
  • Superior temperature stability helps keep your home heated properly
  • Best direct combination boiler


  • Heavy

If you’re fine with spending over $2,000 for proper and optimized indoor heating, look no further than this direct combination boiler.

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Rinnai Q-Series Condensing Boiler

Weight: 82.3 pounds

Dimensions: 10 x 31.50 x 11 inches


  • Not very difficult to set up
  • Available in over 6 styles
  • Made of sturdy stainless steel
  • Compact wall-mounted design saves space
  • Designed with optimal indoor heating in mind


  • Fairly heavy

With a compact and wall-mounted design, this natural gas boiler will enable your home to have proper indoor heating.

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Rheem Tankless Natural Gas Water Heater

Weight: 79 pounds

Dimensions: 18.5 x 9.75 x 27.5 inches


  • Much more affordable than other boilers on this list
  • 94% energy efficient
  • Made with a stainless steel condensing heat exchanger
  • Electronic controls designed to increase energy efficiency and safety in your home


  • You’ll need help setting it up in your home

There’s really not much bad things we can say about this tankless gas boiler. Not only is it 94% energy efficient, it really won’t break the bank.

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Ecosmart Electric Tankless Water Heater

Weight: 14 pounds

Dimensions: 3.63 x 14 x 17 inches


  • Costs less than $500
  • One of the best electric water heaters we’ve ever used
  • Very durable
  • Easy to use and setup
  • Lifetime warranty


  • It will help you save up to 60% on your water heating costs with its advanced technology

If you’re looking for the most affordable gas boiler and water heater on the market, then choose this intelligent tankless model.

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Rinnai RL Series Water Heater

Weight: 44.2 pounds

Dimensions: 9.27 x 14.04 x 26.9 inches


  • Fairly affordable
  • Not heavy
  • Made with modern technology
  • Very efficient
  • Gives you endless hot water for your entire home


  • It's the bang for your buck

The boiler engineers at Rinnai definitely know what they’re doing. Not only is this water heater lightweight, it is made to last you many years of proper and comfortable heating.

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Rinnai Tankless Hot Water Heater

Weight: 47.4 pounds

Dimensions: 9.6 x 14 x 24.3 inches


  • Lightweight
  • Costs less than $1000
  • Available in many styles and prices
  • Produces efficient heating
  • Not very difficult to set up in your home


  • One customer said “this baby rocks”

Customers say they love this hot water heater, and we do too. You can’t get a better deal than this lightweight and affordable gas boiler.

Shop Now
Our Top 5 Picks (Comparison)
Rinnai i150SN Condensing Gas Boiler
  • Best Gas Boiler On The Market
  • Rinnai
Buy Now →
Noritz Indoor Direct Combination Boiler
  • Best Direct Combination Boiler
  • Noritz
Buy Now →
Rinnai Q-Series Condensing Boiler
  • Best Natural Gas Boiler
  • Rinnai
Buy Now →
Rheem Tankless Natural Gas Water Heater
  • Best Tankless Gas Boiler
  • Rheem
Buy Now →
Ecosmart Electric Tankless Water Heater
  • Best Affordable Gas Boiler
  • Ecosmart
Buy Now →

The Basics of Boilers & How Heat is Distributed

So, how does a boiler work? You’ll learn exactly that in this section. First, the boiler’s burner consumes fuel which creates heated combustion gasses. These HCGs then pass through a heat exchanger that transfers heat into the water before being exhausted from the house. Next, the hot water gets circulated through a closed system of pipes all the way to baseboard radiators. 

The hot water can also go through radiant heat floor tubing, which heats the room they’re in by passing hot water through PEX tubes. These PEX tubes are installed in a concrete slab which is attached under the floor. 

The PEX tubes can also be installed in sleepers above the floor they’re installed by. Then, the heat from the water radiates into the living spacer where it circulates, and eventually reaches the boiler where it is reheated. The process then repeats, again and again.

Did you know that controls regulate when the burner fires? Controls also maintain the temperature of the water. When the volume of heated water increases, it is accommodated by an expansion tank. 

If you didn’t know already, an expansion tank (also known as an expansion vessel) is a small tank used to protect closed water heating systems and domestic hot water systems from excessive pressure.

Popular Boiler Terms & Definitions

Below is a list of popular boiler terms you should know the definition of.

  1. Heat Exchanger - A device which converts energy into heat.
  2. Standing Pilot Light - A light which is always burning.
  3. Electric Ignition - When the boiler turns on, it automatically ignites the boiler’s pilot light with electricity.
  4. Boiler Pressure Valve - A device which releases pressure from the boiler. Every boiler is required to have a boiler pressure valve, because if a boiler doesn’t then the pressure will not be controlled.
  5. Vent Damper - This device automatically closes the boiler when it isn’t working. A vent damper can help save energy and keep the boiler working well for more time.
  6. Outdoor Temperature Reset - An electronic thermostat that adjusts the water’s temperature in the boiler to match the temperature outside.
  7. Infinitely Modulating Capacity - A term that means water is continually moving throughout the boiler.
  8. LPG (Liquid Petroleum Gas) - The term that boiler manufacturers use for propane.
  9. Water Velocity - This term refers to the pressure of the water moving through pipes. For smoother operation and fewer problems (and headaches), ensure your boilers’ water velocity is high.
  10. Hydronic Heating - A term that is used sparingly to describe hot water heating.
  11. Heat and Power Boiler - A boiler that produces a limited amount of electricity, heat, and hot water.

Heat Distribution

Most boilers on the market circulate water to baseboard radiators or in-floor radiant heat systems. They do this using a pump or a circulator. Heat distribution is very important to understand before buying a gas boiler, since their primary duty is to properly distribute heat to water throughout your home.

Boiler Size

Did you know that the heating capacity of a boiler is measured in Btu’s of heat it can produce in one hour? To be precise, residential boilers are made in capacities from about 35,000 Btu/h to 399,000 Btu/h. Each gas boiler is made in several sizes to be able to fit in different sized homes.

Boiler Types

Before buying a boiler, you’ll need to consider a few types of boilers. Here they are in a brief overview:

Standard Boilers vs. Condensing Boilers

To compare stand and condensing boilers, we will cover the most important differences. Boilers with AFUE efficiency between 80% and 84% are labeled “standard boilers.” If a boiler has 85% to 90% efficiency, some brands will call them “high-efficiency boilers.” 

A majority of standard boilers are built with cast iron heat exchangers, and tend to be the most affordable models. Most standard boilers meet federal minimum efficiency standards, which makes them safe to buy and use in your home.

What about condensing boilers? Well, condensing boilers can be floor mounted with a large capacity or wall mounted with a small to medium capacity. What sets condensing boilers apart is their high efficiency levels of at least 95% AFUE. This high efficiency is achieved with a complex heat exchanger which maximizes heat transfer. The complex heat exchanger does this through condensing the moisture, and this moisture it condenses is a byproduct of combustion.

Water Boilers vs. Steam Boilers

What about the differences between water and steam boilers? 

It’s important to know that water boilers create water temperatures that never exceed 200F. Unlike water boilers, steam boilers heat the water to the boiling point and then push steam through the system to deliver the necessary heat. Did you know that steam boilers are not very common compared to other types of boilers made. According to Pickhvac, “steam boilers are the minority of boilers made.”

Floor Standing vs. Wall Mounted Boilers

Traditionally, boilers have been installed on the floor of a home, and many still are due to their large size and heavy weight. These boilers are also known as floor mounted or free-standing boilers.

On the other side of the comparison, wall-mounted boilers are known for their “space-saving” and gas-fueled design. Most wall-mounted boilers can be vented through the wall rather than through the roof.

Staged Boilers

Staged boilers are usually high-efficiency and condensing, and they operate in several capacities. This includes low, medium, and high or in capacities that slightly rise and fall. Why would anyone buy a staged boiler? Well, the main benefit of staged boilers is that they deliver more precise heating. This precise heating enhances energy efficiency and keeps your home properly cared for.

Combi Boilers

Combi boilers, also known as combination boilers are units that heat your home and meet your hot water needs. They eliminate the need for owning a separate water heater. You would want to buy a combi boiler because they save space and offer excellent efficiency.

Common Problems with Boilers You Might Encounter (And How To Fix Them)

In this section, you’ll find common problems you might encounter when owning a gas boiler and solutions to help you fix them.

First, you’ll need to know what type of boiler you have. Most boilers produce steam or hot water, and all are either condensing or non-condensing boilers.

So, determine if you have a hot water boiler or a steam boiler. This information is important to know if you ever need to contact a technician. Below is a quick checklist

Home Safety Tips For Gas Boiler Owners

If you use a boiler, you need to make sure you’re checking it every fall to see any possible dangers. It’s recommended for boiler owners to check their boiler at the beginning of the heating seasons. Owners should also check about once a month to look for any possible dangers.

So, what should I check? You might ask. The main thing you should check is the boiler pressure relief valve, which is a device that lets off excess steam or hot water. This device keeps pressure from building up and damaging the boiler. 

It’s pretty simple, actually. All you need to do is glance at this valve and the area around it and look for water or steam coming out of it. But if you notice it looks like water or steam hasn’t been coming out of the boiler recently, make sure to call for professional boiler service.

Next, you’ll want to make sure the valve isn’t blocked. Your priority should be to make sure that people won’t be working, walking, or sitting in areas where they could be hit by steam or hot water from the boiler pressure relief valve.

To prevent fire hazards, make sure nothing is sitting on the boiler or is stored right next to it. This includes materials like paper, plastics, flammable liquids, wood, clothing, and other chemicals that might be stored near the boiler. It is critical that people (and pets) are always kept away from the boiler.

How To Make Sure Your Boiler System Is Running Properly

Below are a few tips to help you make sure your boiler is running properly, so you can stay safe and have a properly heated environment.

  1. Inspect your gas boiler every 12 months
  2. Check the boiler pressure
  3. Keep the area around the boiler clear
  4. Have the boiler services by a licensed technician every 12 months

Where can I buy a gas boiler?

You can buy a gas boiler online:

  1. On
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  3. And on

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