Free, Custom Tankless Water Heater Size Calculator
Choosing the right size tankless water heater is crucial for ensuring your home has an adequate hot water supply while maximizing energy efficiency. Undersizing your unit will result in a shortage of hot water, while oversizing leads to higher upfront costs and wasted energy. Our tankless water heater size calculator takes the guesswork out of selecting the perfect model for your household’s needs. Correct water heater sizing is essential to ensure you make the right choice for your home.
Tankless Water Heater Size Calculator
The calculator considers your peak hot water demand, required temperature rise based on incoming groundwater temperature, and the flow rates of your fixtures and appliances. It then provides a minimum recommended tankless heater size to meet your household’s needs comfortably. Check out our picks for the best tankless water heaters of 2024-2025! We rate electric tankless water heaters, gas tankless water heaters, propane tankless water heaters, and under-counter tankless water heaters!
Factors Affecting Tankless Water Heater Sizing
Several key factors influence the sizing of your tankless water heater:
- Peak demand: Determine the time of day when your home uses the most hot water and how many fixtures or appliances are running simultaneously.
- Flow rates: Calculate the total flow rate in gallons per minute by adding up the flow rates of the fixtures and appliances used during peak demand.
- Temperature rise: Consider the incoming water temperature in your area and the desired output temperature. A greater temperature rise requires a higher heating capacity.
- Household size: Larger households generally have higher peak demands and may require a higher-capacity tankless heater.
Gas vs. Electric Tankless Water Heaters
When selecting a tankless water heater, you must choose between gas and electric models. Gas tankless heaters typically have higher flow rates and can handle larger temperature rises, making them suitable for most whole-house applications. Electric tankless heaters are more compact and energy-efficient but have lower flow rates, which may be sufficient for smaller homes or point-of-use applications.
Frequently Asked Questions
What size tankless water heater do I need for a family of four?
A family of four with two bathrooms typically requires a tankless water heater with a minimum flow rate of 6-8 GPM, depending on the incoming water temperature and simultaneous hot water usage.
Can a tankless water heater provide enough hot water for multiple showers?
A properly sized tankless water heater can provide enough hot water for multiple simultaneous showers. Use our calculator to determine the size based on your peak demand and desired flow rates.
How does the groundwater temperature affect tankless water heater sizing?
Colder incoming water temperatures require a greater rise to reach the desired output temperature. This means homes in colder climates may need a higher capacity tankless heater to achieve the same flow rates as homes in warmer regions. Using our tankless water heater size calculator and understanding the factors influencing sizing, you can confidently select a model that will provide ample hot water for your household while optimizing energy efficiency and performance.
