What is a Combi Boiler? When Boilers and Water Heaters Collide

From boiler installation to tankless hot water heaters, First Call has done it all. To help homeowners understand the difference between your central heating system and water heating system, we’ve put together a helpful guide that explains the differences between a boiler vs. hot water heater, and explain, once and for all, what exactly a combi boiler is and where they fit on the HVAC spectrum.

What is a Hot Water Heater?
The Pros and Cons of a Hot Water Heater
What is a Boiler?
The Pros and Cons of a Boiler
What is a Combi Boiler?
The Pros and Cons of a Combi Boiler

Hot water heaters: making bathing more comfortable since 1889

Fun fact: The first automatic, storage tank-style gas water heater was invented by Norwegian-born mechanical engineer, Edwin Ruud, and the Ruud Manufacturing Company is still in existence today!

Quite simply, a hot water heater heats your home’s water supply so that you can do things like shower, wash dishes, and clean laundry with ease. While there are a few options for water heating systems (standard hot water tanks, PDV hot water tanks, condensing tankless water heaters, etc.) and a variety of fuel options (electricity, natural gas, propane, solar power, etc.) they all essentially serve the same purpose, which is to supply your home’s fixtures and appliances with heated water.

Pros and cons of hot water heaters

Pros

• Plenty of options including budget-friendly standard hot water tanks and high-efficiency tankless water heaters
• Generally, a designated hot water heater provides a stronger water pressure.

Cons

• Their single purpose is to heat your home’s water supply; you still need a secondary appliance such as a furnace to heat your home

What’s hotter than a hot water heater? A boiler, of course!

Boilers also heat water for household fixtures and appliances, but they can be used to heat your home too either by heating the air in a forced-air system, or via radiant heating systems, such as in-floor heating or baseboard radiators. Residential boilers are very energy efficient.

For comparison’s sake, a standard hot water tank is only about 65-72% efficient, whereas certain types of boilers feature energy efficiency ratings of 95%. While boilers are arguably the most versatile home heating option — heating applications include in-floor heating, snowmelt systems, and customizable zone control for different areas of your home — they are also the most expensive with installation or retrofit costs in the range of $15,000 to $50,000.

Pros and cons of boilers and radiant heating systems

Pros

• Meets a high demand for hot water and heats your home
• Versatile heat options include: in-floor heating, baseboard radiators, towel warmers, snowmelt systems
• Energy efficient home heating; water retains heat better than air and with radiant heating systems, you don’t lose heat through duct leaks, which account for up to 30% of lost heat in forced-air systems
• Even, zone-controllable heating
• Improved air quality compared to a forced air furnace which blows dust and allergens throughout your home

Cons

• Expensive installation and retrofit costs ($15,000 to $50,000)
• Large components, such as an indirect hot water tank, take up a lot of space in your home and may not fit in smaller homes if you don’t have extra space for a tank in the loft.
• If it’s a central heating boiler, it usually has to pause from heating the central heating water while it’s heating the hot water, because it can’t supply enough heat to do both jobs at the same time.

And for the Goldilocks in all of us, a combi boiler might be just right

While they have been steadily gaining popularity in North America in recent years, if you’re still wondering exactly what is a combi boiler, you are not alone. Essentially it boils down (yup, we went there) to capacity and convenience, in that “combi” or combination boilers are medium-duty boilers that are ideal for homes with a smaller loft space to provide heating and hot water for your home. Combi boilers can also work with an air handler (coil and fan), baseboard radiators, or an in-floor heating system to heat your home and provide an endless supply of hot water.

Some of the benefits of combi boilers are that they are less expensive to install compared to traditional system boilers, the units are very compact (there is no storage tank for water), and they are relatively simple to install.

Pros and Cons of a Combi Boiler

Pros

• Limitless hot water
• Low running costs and energy efficiency since you are not paying to continuously heat water in a tank
• The space saving benefits of the combi boilers small, wall-mounted unit.

Cons

• Not ideal for large homes or homes with several showers
• Since the boiler has to fire up first to heat water on demand, there’s a slight delay in water heating
• If the combi boiler breaks down, you’ll have cold showers and a cold house
• Less capacity for additional applications compared to a regular boiler

Thinking about upgrading your water heating system? Give us a call at 780.464.3337 to go over some options or request an estimate online.