Switching to a tankless water heater can be a smart upgrade, but deciding which size your home needs can be tricky. Choosing the right size helps protect your system from unnecessary strain while delivering consistent hot water when you need it. From household size to local water temperatures, several factors go into tankless water heater sizing. If you’re considering a tankless water heater in Atlanta or Alpharetta, here’s how to choose the right fit for your home.
Why Tankless Water Heater Sizing Matters
Tankless water heater sizing plays a direct role in comfort, efficiency, and long-term system performance. When a unit isn’t properly matched to your home’s hot water demand, it can create ongoing issues that go beyond inconvenience, such as:
- Problems caused by undersizing: A unit that is too small may struggle to keep up when multiple fixtures run at the same time, leading to temperature fluctuations or reduced flow. Because it has to work harder to meet demand, the system may experience increased wear, more frequent repairs, and a shorter overall lifespan.
- Problems caused by oversizing: Installing a unit that is too large will cost more than necessary, causing you to spend more money upfront than you need to. Oversized systems can also cycle inefficiently, which reduces energy efficiency without providing any extra comfort benefits.
Evaluate Your Household’s Hot Water Needs
Every household uses hot water differently, which is why there’s no one-size-fits-all answer. Start by looking at how many people live in your home and how many bathrooms you have. A one-bathroom home with two occupants typically needs less capacity than a larger household where multiple showers may run back-to-back.
Daily habits matter just as much. Some families shower once a day and do laundry once a week, while others use hot water frequently throughout the day for laundry, dishes, and cleaning. Evaluating these patterns helps narrow down what the right size tankless water heater looks like for your household.
Understand Flow Rate Requirements
Tankless water heaters are sized based on flow rate, measured in gallons per minute (GPM). This number represents how much hot water the unit can produce at one time. The higher the GPM rating, the more fixtures the system can support at the same time.
Different fixtures use different amounts of water. A typical shower may use around 2 to 2.5 GPM, while a bathroom sink uses less. Dishwashers and washing machines also draw hot water, often in short bursts. If multiple fixtures are likely to run at the same time, their GPM requirements need to be added together.
Consider Incoming Water Temperature
Another critical factor is incoming water temperature. Tankless systems heat water on demand, so the unit must raise the water from its incoming temperature to your desired output temperature. This difference is known as temperature rise.
In North Georgia, incoming water temperatures change with the seasons. During cooler months, the water entering your home is colder, which means the system has to work harder to heat it. A larger temperature rise requires more heating power, which directly affects the size of the unit you’ll need. Ignoring this factor can result in a system that struggles during winter, even if it performs well in warmer months.
How To Calculate Your Water Heater Size
To estimate the size you need, combine your flow rate and temperature rise requirements. Here’s how:
- Determine the maximum GPM you expect to use at one time by adding up the fixtures likely to run simultaneously.
- Calculate the temperature rise by subtracting your incoming water temperature from your desired hot water temperature.
For example, if your household needs 6 GPM and a temperature rise of 60 degrees, you’ll need a tankless system capable of handling both at once.
While this provides a general estimate, real-world conditions can vary. Online calculators can be helpful as a starting point, but they shouldn’t be the final decision-maker.
Why a Professional Assessment Is Essential
Sizing a tankless water heater involves more than simple math. Fuel type, venting requirements, gas line capacity, and electrical service all play a role in selecting the right system. A professional plumber can evaluate your home, look at your usage patterns, and make sure your new unit is properly matched to your needs. Proper installation is the best way to make sure your new system will operate safely and efficiently for years to come.
Schedule a Water Heater Installation With Moncrief Today
As your trusted provider of local plumbing services in the Atlanta area, Moncrief Heating & Air Conditioning provides professional guidance, precise sizing, and expert tankless water heater installation for homes across Atlanta, Alpharetta, and North Georgia. With upfront pricing, free replacement estimates, and licensed technicians, you can expect clear communication from start to finish.
Contact our team to schedule your tankless water heater consultation with Moncrief Heating & Air Conditioning. We’ll help you find the right solution for your home in Atlanta or Alpharetta!
