The 4 Best Condensing Boilers – Reviews 2023

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Photo by Kaustav Bhattacharya / CC BY

If you’re looking to replace an old boiler in your home, you’ve definitely been looking at condensing boilers (a.ka., tankless water heaters). In the US, all new boilers have to be condensing units since 2005 and that’s probably a good thing due to the increased efficiency. A modulating condensing boiler often functions at around 90% efficiency or more, while conventional models range from 70% to 80%.

There’s a lot that goes into picking one of these units for home use, so let’s take a look at 4 of the best condensing boilers on the market. Keep in mind that the average shower head, the largest use of heated water in most homes, uses about 2.1 gallons per minute. After we’ve taken a look at these, we’ll talk a little bit more about how to choose the best one to make sure you have an endless supply of hot water for your home.

Rinnai RL94iN Natural Gas Tankless Water Heater

Running at up to 9.4 gallons per minute, this boiler can power most homes’ water needs quite easily. It comes out of the box with recirculation capabilities as well, which can help you save on your water bill as well as your electrical. The best part is that this boiler (see full specs) won’t take up much room, and you’ll be able to quite easily fit it somewhere since it’s about the size of a small suitcase. With easy to use controls as well, it makes a great solution for your household’s hot water needs, and it’s one of the best-reviewed modulating condensing boilers out there.

Rinnai Water Heaters - Other things you should know

Takagi T-H3-DV-N Condensing Indoor Tankless Water Heater

This boiler from Takagi can power an astonishing four bathrooms in most climates, although in some of the colder places in the world you may only be able to get three going. It puts out an insane amount of BTUs and has a flow rate that borders on ridiculous. Even better, the installation is easy enough that most home owners should be able to quite easily complete it with the included manual, although be aware it’s going to take a considerable amount of time. Hands down, it’s one of the best condensing gas boilers you can buy.

Installing - Takagi Tankless Water Heaters

Rinnai RU98IP 9.8 GPM Indoor Tankless Propane Water Heater

The Rinnai RU98IP is a high-volume, propane powered unit. While it might not be ideal for everyone, due mainly to the power source, if you’re willing to purchase the propane to use with it you’re in good hands. It’s extremely efficient and comes in with a stunning 199k BTUs so you can be sure that it will heat your water no matter what the climate. The only real issue here is, of course, the energy source, which can be inconvenient for those who’d rather use their utilities to keep the water hot. But if you’re okay with propane as a source, this is easily one of the best condensing boilers on the market.

Takagi T-T-KJr2-OS-LP Outdoor Tankless Water Heater, Propane

This unit is a little bit older, but an outdoor, propane fired unit might be exactly what some people need. This unit puts out 6.6 gallons per minute, so it might not suit everyone’s needs but for most residential households there won’t be any issues. It’s also designed to be placed outdoors, making it perfect for those who don’t have a garage or other place to stick their equipment indoors. The internal freeze protection means that you won’t have to worry about things getting frozen up, and you’re sure to love it since you won’t have to find somewhere to place it.

Why Get a Condensing Boiler?

The answer to this question is really simple at the end of the day, and consists of three words: endless hot water.

Most of us have had to contend with running out of hot water at some point, whether it was in the middle of a shower or while de-icing something, and it’s inconvenient at the best of times and downright awful at the worst. A modulating condensing boiler will allow you a constant flow of hot water into your home, which means you can shower for as long as you’d like without having to worry about suddenly getting cold.

They’re also quite energy efficient, making for a cheaper-to-run unit than traditional boilers or water heaters. It’s win-win.

How to Select the Right Condensing Boiler

While it might be tempting to select only the highest gallon per minute, you also have to take into account several other factors while you’re looking into getting the best condensing boiler possible.

The gallons per minute is an important consideration, but keep in mind that the average shower only uses around two gallons per minute so you’ll be covered pretty much no matter what as long as you go with a high-quality product.

The other primary consideration is the energy source. The majority of the top condensing boilers will run on natural gas, and can thus be tapped directly into your utilities but a number of them will also run on propane. This will mean that you need to keep a couple of tanks around in order to make sure that you don’t run out of hot water, but will also make you less reliant on the energy grid in the case of something happening or a repair being needed somewhere along the line.

Finally, you’ll need to figure out where you’re going to place your new unit. Some of us have to place them outdoors, which isn’t suitable for every boiler due to issues with freezing. An outdoor model will have protections built into it. As a general rule, condensing boilers are smaller than most of your other options, so space shouldn’t be an issue.

From there it’s mostly a matter of preference, the controls are similar and as a general rule units that cost more in the beginning will last you longer and require less maintenance and repairs done over the years. One of good quality and reliability can last you for a couple of decades, which makes the small initial investment more than worth it as time goes on.

If you’re ready for endless hot water and lower energy bills, then take a look into investing in the best condensing boiler you can find. You’ll be glad you did as soon as it’s installed. Good luck!

  • Founder of Mechanical Caveman, Beau is an unrepentant tool enthusiast and, sporting deadlift-callused hands and an incongruous beer belly, all-around macho guy. When he doesn’t know re tools, he consults with his handyman and car-repairman buds to give you well-reasoned and cutting-edge info.

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