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Traditional water heaters with their bulky storage tanks have been a household staple for decades.
Yet many homeowners don’t realize there’s a far more innovative solution available.
Those large basement tanks that constantly heat and reheat stored water are becoming outdated as leading manufacturers introduce more efficient tankless technology.
We’ve spent years testing and installing various water heating systems, and the shift toward tankless units represents a genuine advancement in home water heating.
But how exactly does a water heater function without a storage tank?
Our team of plumbing experts will break down the fascinating technology behind tankless water heaters, exploring everything from gas and electric models to whole-house and point-of-use systems
First, to help understand how hot water heaters work, check out this informational video from Rinnai.
Through our extensive hands-on experience with water heating systems, we’ve found that grasping the fundamentals of tankless technology is crucial before making a purchase decision.
These innovative systems heat water directly using gas or electricity, delivering it straight to your fixtures without any storage tank involvement.
Instead of keeping a large volume of water hot all day, these units spring into action only when you need hot water, heating it instantly on demand.
We categorize tankless water heaters based on three primary factors: fuel type, flow rate, and application type.
While there are many other technical specifications to consider, these core differences provide an excellent foundation for understanding both electric and gas tankless systems.
Let’s examine how each of these key features affects your water heater’s performance.
In our professional installations, we’ve found that fuel type is the most crucial factor in determining how a tankless water heater operates.
This choice typically becomes the first major decision for homeowners exploring tankless options.
While most units run on electricity or natural gas, we’ve also worked with systems powered by solar, geothermal energy, fuel oil, and propane.
From our experience, local utility costs and availability usually guide this decision.
Gas tankless systems have consistently proven superior for high-demand situations in our installations.
They deliver more hot water faster than other options, making them ideal for larger households.
We’ve observed that gas remains the preferred choice in most regions due to its widespread availability and cost-effectiveness.
However, we always warn our clients about installation complexities – particularly the venting requirements that can add significant cost and complexity.
Electric tankless heaters shine in different scenarios.
Through our testing, we’ve found they work beautifully for average or lower demand situations.
While they typically max out around 8 GPM (gallons per minute), this output suits most smaller families perfectly well, though it falls short of gas models’ capabilities.
Based on our installation history, electric models often appeal to budget-conscious homeowners.
They’re typically less expensive to buy and install, with significantly simpler installation requirements than gas units.
We regularly recommend electric models for vacation homes or situations where minimal maintenance is preferred, as they’ve proven more reliable with less upkeep than their gas counterparts.
In our daily work with tankless systems, flow rate emerges as a critical consideration for proper sizing.
Measured in Gallons Per Minute (GPM), this specification tells us exactly how much water the unit can heat effectively at any given moment.
Think of it as your heater’s “hot water bandwidth” – it’s the maximum amount of heated water your system can deliver to your appliances per minute.
Through our installation experience, we’ve learned that calculating your home’s required GPM involves adding up the flow rates of all appliances you might run simultaneously.
This typically includes your everyday water users: sinks, dishwashers, and washing machines.
A crucial factor we’ve discovered is that geographic location plays a significant role in heater performance.
Homes in colder regions, where groundwater temperatures are lower, need systems that work harder to achieve desired temperatures.
This brings us to an essential concept called “temperature rise.”
Temperature rise indicates how many degrees your unit can warm the water while maintaining its stated GPM.
For example, when you see a specification like:
11.5 GPM @ 45 Rise Capacity
Our team interprets this to mean the unit can heat water by 45 degrees while delivering 11.5 gallons every minute.
Based on our field testing, this means you’ll have endless hot water as long as you stay under 11.5 gallons per minute and your groundwater temperature remains at least 75 degrees.
For a deeper dive into selecting the right size for your needs, check out our [sizing article].
After years of installations, we’ve found that choosing between whole-house and point-of-use systems is another key decision in the tankless journey.
While both types operate on the same basic principles, their applications can require specific features based on your needs.
Whole-house systems have been our go-to solution for most residential installations.
These units serve as the primary heat source for your entire home from a single location.
In our experience with larger homes, we sometimes recommend “ganging” multiple compatible units together to boost overall capacity when a single unit isn’t sufficient.
One important consideration we always discuss with clients is heat loss through piping.
We’ve found that the greater the distance between your heater and fixtures, the more heat you might lose along the way – just like with traditional tank systems.
Point-of-use systems offer a different approach that we’ve found particularly effective in specific situations.
These compact units are installed directly where you need hot water – typically within two feet of the fixture they serve.
Through our installations, we’ve discovered they work perfectly for remote fixtures far from the main heating system or in locations where connecting to the primary system proves challenging.
Based on our extensive testing and installation experience, we can explain exactly how electric tankless systems deliver hot water on demand.
You might hear these units called “on-demand” water heaters, and there’s a good reason for this name.
Unlike traditional tank systems that constantly store and heat water, these smart units only activate when you need hot water.
Here’s what happens when you turn on a hot water tap:
First, a highly sensitive flow sensor detects the water movement.
This triggers the electric heating elements, which instantly warm the water as it flows through the unit.
The heated water then travels directly to your fixture, providing immediate hot water without any storage or waste.
Throughout our years of installing both electric and gas systems, we’ve found that gas models operate on a similar principle but with one key difference.
Instead of using electric heating elements, gas tankless units employ what we consider the heart of the system: the heat exchanger.
This sophisticated component consists of a series of tubes that pass near powerful gas burners, efficiently transferring heat to the water flowing through them.
The heat exchanger’s role is crucial – it’s the engineering marvel that makes gas tankless systems so effective at delivering consistent hot water.
Our installation experience has taught us that proper sizing remains critical regardless of fuel type.
In fact, many skeptics of tankless technology we’ve encountered simply had undersized units that couldn’t meet their household demands.
Let’s look at some real-world examples from our installations:
For a couple in a small apartment with a single bathroom and no laundry facilities, we often recommend a 5 GPM unit.
The Rheem RTEX-36 Electric Tankless Water Heater perfectly suits these needs at an affordable price point.
However, for a typical family of four, our calculations usually indicate a need for at least 9.5 GPM to handle multiple simultaneous hot water demands.
In our installations, we’ve found that point of use tankless heaters operate on the same basic principles as their whole-house counterparts.
The main distinction lies in their placement – these compact units are designed to be installed within two feet of their designated fixture, often tucked away under a sink.
They spring into action the same way: a flow sensor detects water movement, triggers the heating process, and delivers hot water directly to your fixture.
What sets these units apart is their space-saving design.
Since they’re installed in living spaces rather than utility areas, manufacturers have engineered them to be remarkably compact.
However, we always inform our clients that this smaller size means reduced power capacity – making these units perfect for single fixtures but unsuitable for high-demand applications.
Now that you understand the innovative technology behind tankless water heaters, you might be considering an upgrade from your traditional tank system.
Our team has tested countless models, and we can confidently say that modern tankless systems offer significant advantages over conventional tanks.
Ready to explore your options? Take a look at our carefully curated selection of high-efficiency tankless water heaters from industry leaders like Rheem, EccoTemp, and Titan!
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