What Size Water Heater Do You Need?

Understanding Water Heater Sizes

Water heaters come in various sizes, typically measured in gallons for tank models or in flow rates for tankless models. The size you need depends largely on your household’s hot water usage. Let’s break down the factors you should consider:

1. Household Size and Number of Fixtures

A simple way to estimate your water heating needs is to look at the number of people in your home and the number of water fixtures you have. The more people in your home, the more hot water you’ll need. If you have large bathtubs or showers with multiple shower heads, they will use more hot water.

So while a 40-gallon tank might satisfy a typical household of 3 people, you might need a larger tank or even a tankless system if you have high-volume fixtures.

2. Peak Hour Demand

Peak hour demand refers to the maximum amount of hot water used during the busiest hour of the day. To estimate this, consider your household’s morning routine:

• Showers
• Dishwashing
• Laundry
• Handwashing

Each of these activities consumes a certain number of gallons per minute (GPM). By calculating the total GPM used during peak times, you can better determine the necessary gallon capacity for a tank-type model or the appropriate size for a tankless water heater.

3. First Hour Rating (FHR)

For tank-type water heaters, the First Hour Rating (FHR) is a critical metric. It indicates the number of gallons of hot water a heater can supply per hour, starting with a full tank. Look for water heaters with an FHR that exceeds your household’s peak hour demand. You’ll want your water heater to exceed your expected demand so that you don’t fall short – especially since the FHR number is based on a simulated usage test, and is not necessarily an accurate representation of what the water heater will actually deliver.

4. Flow Rate for Tankless Heaters

Tankless water heaters are sized based on the flow rate and temperature rise needed. The flow rate is measured in Gallons Per Minute (GPM), and the temperature rise is the difference between the incoming water temperature and the desired output temperature. Ensure the tankless unit you select can handle your household’s peak hot water demand without compromising performance.

Other Considerations

Energy Efficiency

Selecting the right size water heater is not just about meeting your hot water needs; it’s also about energy efficiency . An oversized water heater can lead to higher energy bills due to unnecessary heating. Conversely, an undersized unit may have to work harder and longer, reducing its lifespan and efficiency.

Professional Advice

While this guide provides a solid foundation for understanding your water heater needs, consulting with a professional can offer personalized insights. A pro can assess your specific situation, consider variables such as local climate and plumbing layout, and recommend the most suitable water heater size.

Find a Plumbing Professional

Choosing the right water heater goes beyond size; installation quality and proper maintenance are equally important. To ensure you get the best advice and service, it’s wise to consult experienced professionals. Use our Contractor Directory to connect with professionals in your area who can guide you through the selection and installation process.