If you're researching efficient ways to heat your home and your water without using bulky tanks, you've probably come across the term "boiler tankless water heater." It sounds a bit technical, but the concept is actually simple—and for many households, incredibly practical.
What Is a Boiler Tankless Water Heater?
A boiler tankless water heater is a system that uses your home's boiler to instantly heat water without a storage tank. Rather than keeping water hot all day in a tank (and losing heat while it sits), this system heats water only when you need it—on demand.
It’s also called a tankless coil system, and it works best in homes that already have a boiler for heating.
How Does It Work?
Here’s a quick, step-by-step overview:
Your home’s boiler heats up to warm your space.
When you turn on a hot water tap, cold water flows through a coil inside the boiler.
The coil quickly absorbs heat from the boiler and transfers it to the water.
You get hot water instantly, without needing to wait for a tank to refill.
No tank. No long waits. No wasted energy keeping water hot when you’re not using it.
Benefits of a Boiler Tankless Water Heater
On-Demand Hot Water: Heats water only when you need it.
Space Saver: No large water heater tank taking up floor space.
Energy Efficient (in colder months): Since your boiler is already running, it makes sense to use that heat for hot water too.
Lower Upfront Costs: If you already have a boiler, adding a tankless coil can be more affordable than installing a separate hot water tank.
Things to Know Before Installing
Like all systems, boiler-based tankless water heaters aren’t perfect for every household. Here’s what to consider:
Seasonal Efficiency: These systems work best in the heating season, when your boiler is already running. In warmer months, they can be less efficient because the boiler fires up only for hot water.
Inconsistent Temperatures: Water temperature may fluctuate, especially if multiple taps are running.
Not Ideal for Large Households: If several people are using hot water at once, the system may not keep up.
Maintenance Tips
Flush the coil regularly to prevent mineral buildup—especially if you have hard water.
Schedule annual boiler maintenance to keep the system efficient and safe.
Add a mixing valve for better temperature control and scald protection.
Is It the Right Choice for You?
A boiler tankless water heater is great for:
Homes already using a boiler system for heat
Small to medium-sized households
People looking to save space and simplify plumbing
Budget-conscious homeowners wanting an efficient solution without installing a new tank
But if you live in a warm climate (where your boiler sits idle for months) or your family uses a lot of hot water at the same time, consider a standalone tankless water heater or an indirect water heater as an alternative.
A boiler tankless water heater offers a smart, space-saving, and energy-efficient way to meet your hot water needs—especially if you're already relying on a boiler for heat. Like all systems, it has its pros and cons, but for many homeowners, it’s a perfect blend of performance and practicality.
Looking for help deciding or need a recommendation for a local installer? I’m here to help—just ask!
