Pros and Cons of Combi Boilers

It’s no secret that combi boilers are best employed for specific use cases when it comes to home types. But what about the other pitfalls they might present? Just as important, where do combi boilers build their value? To help answer these questions, we can take note of the pros and cons of combi boilers.

Monkey Wrench Plumbing, Heating, Air & Electric installs and services combi boilers and has done so for over 15 years in Los Angeles County. In that time, we’ve built out a solid roster of technicians specifically suited for combi boiler installation and repair. Now, we’re taking that knowledge and funneling it down into a convenient list of pros and cons.

By the end of this article, you’ll have an idea of where combi boilers excel and where they may prove divisive. With this information, you’ll be ready to start thinking of whether a combi boiler is truly the right fit for your home.

Let’s kick things off with the pros of combi boilers before transitioning into their pitfalls.

Pros of Combi Boilers

There’s no shortage of pros when it comes to combi boilers. While these units won’t be for everyone, the list of benefits may make a decent case for installing one. Whether a combi boiler is right for your home is a bigger question than just addressing its benefits, though.

The following list is meant to give you a jumping-off point for further research and consideration.

Two-in-One Design

Perhaps the most significant benefit of a combi boiler is its ability to pull double duty when it comes to heating. While standard tankless water heaters, which closely resemble combi boilers, provide endless hot water to your home, a combi boiler handles both water and space heating.

This two-in-one design eliminates the need to split your heating components. Maintenance can be handled in a single call rather than calling out a plumbing and HVAC technician separately.

Compact Space Saver

Going along with the two-in-one design of combi boilers is their compact nature. Not only do these units pull double duty, but combi boilers take up far less space than having two separate heating components.

If you’re switching over to a combi boiler for the first time, the freed-up space from eliminating one heating element can be used for other applications like storage. This factor can be a game changer in smaller homes where combi boilers are at their best, but more on that later.

High Efficiency

Aside from their core design saving you space, modern combi boilers boast high efficiency. In states like California, where gas and energy restrictions are tightening, having a high-efficiency way to heat your home and water is an optimal path to futureproof your home.

Many of the best combi boilers, like those from Navien, feature Uniform Energy Factor ratings (UEF ratings) of 94% or higher. This efficiency means potentially lower monthly bills, thanks to the on-demand nature of combi boilers that only heats when called on.

On-Demand Hot Water

Just like a tankless water heater, a combi boiler provides hot water on demand. However, this is not to be confused with instant hot water. The core water heating technology of a combi boiler warms water as needed but still takes a minute to clear the already cooled water stuck in the line.

Still, many homeowners enjoy not wondering if there will be enough hot water to shower if they’re last in line. It’s a bit of a trade-off, so you’ll have to decide what your priorities are: instant hot water or endless hot water. Despite not being included in basic installations, you can get instant hot water by adding on a recirculation pump and return line.

All of these pros sound great, but we would be remiss if we didn’t fill you in on the cons of combi boilers as well.

Cons of Combi Boilers

As with any investment, you’ll likely need to make some concessions at some point. While we’re not advising you to settle, we are openly acknowledging the drawbacks of combi boilers so you can get the full picture and ultimately decide if this is the right path for your home. Let’s jump in with the antithesis to the benefit of having a two-in-one design.

Eggs in One Basket

While we stated that the two-in-one design of combi boilers is one of their greatest strengths, it can also end up being a drawback. For instance, if your combi boiler breaks down, you won’t have access to space or water heating.

With other systems that split these heating components, you at least have some peace of mind when one is on the outs. Overall, having a two-in-one design is beneficial. Still, this pitfall is one to take note of if you’re in an area with severe weather, less stable power grids, or anything else that might interrupt your home’s heating system.

Aside from the potential to lose both water and space heating, a couple more aspects of combi boilers are directly tied to their dual design.

Space Heating Cuts Out with Hot Water Demand

Another major drawback of combi boilers is their inability to heat your home and water at the same time. Because combi boilers feature a complicated design that requires water to be heated at different temperatures, the unit has to take an extra step before providing hot water to a fixture.

Combi boilers initially heat water for space heating, which is at a much higher temperature than what is safe for domestic hot water production. When you demand hot water at a fixture, the combi boiler cycles the hot water through a thick plate, where it is mixed with cold water to bring it to a safe temperature for faucet or showerhead use.

This pitfall means that combi boilers are not always the best option for larger homes, where it takes more to heat the space as opposed to a smaller home. In short, it’s easier to keep a small space warm than a large one.

Can Be More Expensive

Combi boilers may handle space and water heating, but you’ll likely pay a pretty penny for that functionality. Because combi boilers combine a tankless water heater with a boiler, you can expect that utility to be reflected in the cost.

On average, you can expect a combi boiler to cost somewhere between $2,200 to $6,000. You can expect major brands like Navien and Noritz to hit the same price range, with other brands like Rinnai landing lower in the range. But that price range is elevated with installation.

Complex Installation

Combi boiler installation can be tricky since you’ll need a technician who is skilled in both HVAC and plumbing. In some cases, you may have to call out two separate contractors to get your combi boiler installed correctly.

A common issue we run into in the field is combi boilers having problems due to improper installation. In general, only a handful of installers are specially trained in combi boiler installation. As a note, it is in your best interest to thoroughly vet your chosen installer to ensure they are certified for combi boiler installation.

Overall, including the unit, your total investment after installation will likely hit between $12,000 to $26,000. But when is that investment really worth your trouble? Realistically, there are few use cases for a combi boiler in Los Angeles County.

Only Compatible with Certain Homes

You might have guessed by now that combi boilers have a particular use case. Depending on your region, fewer homes may be compatible with a combi boiler since they fulfill a specific set of heating needs.

The main factor in determining whether a combi boiler is right for you is the existence of some kind of hydronic space heating system. These systems include radiators throughout your home or in-floor radiant heating systems where heated water runs through tubes in the floor.

Without these systems in place, there’s no need for a combi boiler. If you’re interested in still getting hot water on demand, a tankless water heater might be a better option for your home.

And with that point, let’s wrap up the pros and cons of combi boilers.

Do the Pros of a Combi Boiler Outweigh the Cons?

We’ve run through the pros and cons of combi boilers to give you a better picture of whether one of these units might be for you. While we can lay out all the facts, you’re the only one who can decide if a combi boiler is worth the investment. With this information, however, you’ll be able to jump-start your research and be well on the way to nailing down a viable heating system for your home.

For over 15 years, we’ve worked to master the ins and outs of combi boiler installation. In that time, we’ve learned that when these units are appropriate, they provide excellent performance and value.

If you want to speak with a technician about upgrading to a combi boiler or swapping out an old unit, click one of the buttons below or use our convenient online scheduler to make an appointment.