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Residential Boilers: How to Choose the Best For Home Heating Today

by Stewart Unsdorfer


Most U.S. homes are heated with either furnaces or boilers. As the temperature starts to drop our natural tendency is to consider if our homes are ready to handle the next heating season.

This article/guide is specifically geared toward the homeowner looking for more information on residential boiler systems; common boiler fixes, features, considerations before a new purchase, energy efficient upgrades and top brands.

Since half of the energy used in your home goes to heating and cooling (according to Energy Star), making smart decisions about your home's heating system can have an effect on your utility bills.

And let's not forget your comfort.

Now is the ideal time to check your boiler and make sure it is working properly. If it isn't, or if it is getting old, you might consider purchasing one of the newer boilers on the market. 

Common Problems with Boilers You Could Encounter

There can be one or two minor problems when your system is first started for the season. Unfortunately, you usually learn about these common problems when it's already cold outside, making the need to address the issue much more urgent.

Let's face the most common problems you might encounter first, before you take a look at a newer energy efficient boiler.

You'll need to know what type of boiler you have. Most produce steam or hot water using natural gas or heating oil, and all are either condensing or non-condensing. While these systems differ in their controls they both utilize a boiler.

Your first step will always be to determine if you have a hot water boiler or a steam boiler. If you don't see a circulator (pump on a hot water heating system) or if you have a clear glass tube on one side of your boiler then it's a steam boiler. Good to know if you have to contact a technician.

Here's a quick check list before calling in the cavalry:

1. Check Your Pilot Light

The problem could be as simple as a draft blowing the pilot out. Or it could be debris clogging the gas delivery nozzle. Checking the pilot light is a consideration if you have either a hot water or steam boiler.

2. Investigate Loss of Pressure  

This commonly occurs because of a water leak somewhere in the system. However, the cause could also be due to a faulty pressure relief valve. In order to determine the cause, it's best to contact a professional who will be able to pinpoint and repair the problem quicker than you can on your own.

In the case of the steam boiler, you can check the water level at the site glass. The site glass should be filled up 3/4 of the way.

3. Could You Have a Faulty Thermostat?

Thermostat issues are exactly as they sound. If yours is inaccurate, or is not operating properly then you must replace it. This is something that you can typically replace on your own.

4. Is There a Deep Rumbling Coming From the Boiler?

The noise you hear is called - Kettling. Not the best sign for the health of your boiler. Probably at the top of the list of the most common problems with boilers is limescale buildup within the boiler's heat exchanger. Cleaning the system will take care of that problem. Probably best to call a professional to "err" on the side of caution.

Key Boiler Features and Advantages

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Consumer Reports wrote a Boiler Buying Guide discussing Condensing vs. Non-Condensing and Sealed Combustion vs. Non-Sealed Combustion.

"All boilers are either condensing or non-condensing. A condensing boiler concentrates water vapor produced in the heating process, and uses waste heat to preheat cold water entering the boiler. Condensing boilers are extremely energy efficient because they can provide ample heat while operating at lower temperatures.

Non-condensing boilers typically operate at higher temperatures, and some heat ends up being vented outside. Non-condensing boilers are 80 percent to 88 percent efficient, while condensing boilers have efficiencies greater than 88 percent."

"Boilers are either sealed-combustion or non-sealed combustion units. You should buy one that is sealed combustion because it brings outside air into the burner and directs exhaust gases outside. Non-sealed combustion boilers draw heated air in and then send it up the chimney, wasting the energy used to heat the air. Also, sealed-combustion boilers won’t introduce dangerous gases into your home." 

What to Consider Before Making the Buying Decision

There are several things to consider when purchasing new residential boilers. There are so many options available that it is important to know which ones are best for your situation. 

Top 3 Things to Consider are Size, Venting Style, and Efficiency:

Size - Consider your climate

When it comes to size, too large is just as troublesome as too small. A boiler that is too small won't do a good job, and one that is too large will waste energy. A general rule of thumb for determining the size you need is actually based upon the climate you live in. Figure about 20 BTU per square foot for a warm climate, 35 for a moderate climate, and 50 BTU per square feet in colder climates. 

Venting - Open area important

Residential boilers that vent directly through the chimney can be located in smaller, closed-in areas. If the boiler is vented by forcing air through a venting system, it will need to be located in an open area that allows it to gather air to use.

Efficiency - Check your numbers

An EnergyStar rating on your boiler will indicate that the unit is energy efficient, therefore saving you money. You want to look for an oil boiler that has at least an 80 percent rating, or a gas boiler that runs at an 89 to 98 percent efficiency. Boilers that run on electricity normally run 100 percent efficient because they produce no waste.

When it comes to efficiency what are some of the differences...

High Efficiency vs Standard Efficiency Boilers

If your unit is more than 10 years old, you will probably save by installing a new system. However, it can be confusing to know what type of boiler is best for your home.

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What Makes a Boiler High Efficiency?

The way a boiler works is by heating water which is conducted through radiators, radiant floor systems or a coil. With a standard boiler, some of the energy that is used to heat the boiler, whether it is a fossil fuel or natural gas, is lost in the process of conducting.

A high-efficiency boiler is designed to trap the escaping heat and direct it back into heating the home.

Why is High Efficiency Important?

Low efficiency means that fuel is wasted. Boilers over 10 years old only have efficiency ratings of 50-70%. That means they use 50-70% of the fuel to heat the house and the remaining 30-50% of the fuel is wasted.

Along with saving fuel costs, a high efficiency boiler will also help the environment. Because it uses less fuel, it creates less pollution. According to the calculations by ENERGY STAR, 29% of your home's fuel use is in heating. In especially cold climates, that percentage can be even higher. The most significant thing you can do to reduce your home's impact on the environment is to have an efficient heating system.

What is the Difference in High Efficiency vs. Standard Efficiency?

The Federal Trade Commission requires that new boilers display their Annual Fuel Utilization Efficiency (AFUE) so consumers can compare them.

Here are the ratings:

  • Old, Low-Efficiency Boilers have 56% -70% AFUE
  • New, Minimum Efficiency Standard Boilers have 78% AFUE
  • New, Mid-Efficiency Boilers have 80-83% AFUE
  • New, High Efficiency boilers have a 90-98% AFUE.
High Efficiency Boilers vs. Standard and Energy Costs

Because high efficiency boilers are so good at converting fuel into useable heat, they reduce the amount of fuel needed to heat your home, which also reduces the cost.

How much of a savings depends on the AFUE of the boiler it is replacing. The U.S. Department of Energy suggests that if you are replacing an old boiler with a new high efficiency one, you may reduce your fuel bills in half.

High Efficiency vs. Standard Boilers Replacement

High efficiency boilers generally cost more to install than standard boilers for the following reasons:

  • Initial cost of high efficiency boiler unit is higher.
  • Retrofitting a house to handle a high efficiency boiler may cost extra.
  • Repair and installation of high efficiency boilers may be more expensive because they have more complicated technology.

Offsetting these higher costs is the fact that many homeowners can buy a smaller high efficiency boiler, which reduces the cost.

Boiler Ratings by Brand 

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Furnace Compare has collected thousands of reviews from homeowners since 2006 and lists its top 19 choices based on consumer reviews.

Visit the link for full coverage of the reviews, but take a look at their top five residential boilers on the market right now:

1. Bosch - This received a positive review by 89% of the customers and reached #17 out of 67 brands. Bosch produces 9 models of gas tankless water heaters, including the the Greentherm C 1050 Condensing and the Greentherm C 950 ES Condensing, which are Energy Star Rated. 

2. Slant-fin - Following so close, Slant-fin received a positive review by 83% of the reviewers and reached #19 out of 67 brands. Slant/Fin manufactures a number of high-efficiency residential gas and oil-fired boilers, including several in the Eutectic line that the company says are the quietest in the industry.

3. Westinghouse - 72% of consumers recommended this boiler, ranking it #21 out of 67 brands. A number of air conditioner, furnace and heat pump options are available under the Westinghouse brand. Systems run on the side of high-efficiency, with a range of 13 to 25.5 SEER for cooling units and 80 to 97 percent AFUE for furnaces.

4. Lennox - Lennox ranked at #33 out of 67 and was recommended by 63% of consumers. 

5. Crown - Rounding out the Top Five, this brand reached a rank of #35 out of the 67 brands of boilers. And was recommended by 56% of its customers.

Residential boilers are growing in popularity and may be the system of choice for your family. According to Lifestyle Comfort Solutions, they are "no longer the monster in the basement with clanking radiators in each room, today’s residential boiler is compact, and comes in a variety of efficiency ratings, at least 80% AFUE mandated by law." 


If you have an older boiler in your home you should consider installing a modern boiler system. Modern boilers are smaller and, far more efficient than older models.

Shopping for a new boiler system can be confusing because you'll be confronted with all sorts of terms that you might never have heard before. If you are in the midst of shopping, there is a list of some of the popular boiler terms that can be found in the ebook below.

It also gives you a concise manual on how a residential boiler system works, more details on the types and maintenance.

Did I leave anything out?

Let me know in the comments below...

Download the eBook version of the Ultimate Guide to Home Boiler Systems


Topics: Boilers

blog author

Stewart Unsdorfer

Stewart has been in the HVAC business for more than 25 years. He is a state licensed heating and A/C contractor, as well as being certified in design, fabrication, layout and installation of forced air heating / cooling systems.

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