How to Determine the Tankless Water Heater Size That’s Just Right for You: A Step-by-Step Blueprint
What To Know
- The flow rate is the amount of water that a tankless water heater can deliver per minute.
- Select a tankless water heater with an input capacity that is equal to or slightly greater than the required input capacity.
- An undersized tankless water heater may not be able to meet your hot water demand, resulting in insufficient hot water or fluctuating water temperatures.
Choosing the right tankless water heater size is crucial to ensure an adequate supply of hot water while avoiding energy waste. In this comprehensive guide, we’ll delve into the factors that influence tankless water heater size determination and provide step-by-step instructions to help you make an informed decision.
Factors to Consider
Before calculating the tankless water heater size, consider the following factors:
- Peak Hot Water Demand: Determine the maximum amount of hot water used simultaneously in your household. This includes showers, sinks, dishwashers, and laundry machines.
- Flow Rate: The flow rate is the amount of water that a tankless water heater can deliver per minute. This is typically measured in gallons per minute (GPM).
- Temperature Rise: This is the difference between the incoming cold water temperature and the desired hot water temperature.
- Efficiency: The efficiency of a tankless water heater is measured by its Uniform Energy Factor (UEF). A higher UEF indicates greater efficiency.
Step-by-Step Instructions
1. Calculate Peak Hot Water Demand
List all appliances and fixtures that use hot water and determine their flow rates. Sum these flow rates to get the peak hot water demand.
2. Convert to Flow Rate
If the peak hot water demand is not already in GPM, convert it using the following formula:
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Flow Rate (GPM) = Peak Hot Water Demand (gallons) / 60 minutes
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3. Determine Temperature Rise
Subtract the incoming cold water temperature from the desired hot water temperature.
4. Calculate Heat Load
Multiply the flow rate by the temperature rise to get the heat load in British Thermal Units per hour (BTUH):
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Heat Load (BTUH) = Flow Rate (GPM) x Temperature Rise (°F) x 500 BTU/gallon
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5. Adjust for Efficiency
Divide the heat load by the UEF of the tankless water heater you’re considering. This will give you the required input capacity of the heater.
6. Choose a Size
Select a tankless water heater with an input capacity that is equal to or slightly greater than the required input capacity.
Additional Considerations
- Simultaneous Usage: If multiple appliances are likely to use hot water simultaneously, consider increasing the tankless water heater size to ensure adequate flow rate.
- Future Expansion: If you anticipate adding more appliances or fixtures that use hot water, choose a slightly larger tankless water heater to accommodate future needs.
- Fuel Type: Tankless water heaters can run on natural gas, propane, or electricity. Consider the availability and cost of fuel in your area.
Frequently Asked Questions
Q: What happens if I choose a tankless water heater that is too small?
A: An undersized tankless water heater may not be able to meet your hot water demand, resulting in insufficient hot water or fluctuating water temperatures.
Q: What are the benefits of a tankless water heater?
A: Tankless water heaters provide an endless supply of hot water, are energy-efficient, and have a longer lifespan than traditional water heaters.
Q: How often should I have my tankless water heater serviced?
A: It is recommended to have your tankless water heater serviced annually to ensure optimal performance and longevity.
