Kw and watts calculator for water heater and sizing a tankless water heater calculator

 

A kW calculator for a water heater is a calculation tool to find out the electrical power (in kW) needed to increase the water temperature. This calculation is especially helpful in sizing tankless (on-demand) water heaters or finding the energy demand to a system.

 

Tankless Water Heater Sizing

Flow Rate (Total GPM): Incoming Water Temperature (°F): Desired Water Temperature (°F): Efficiency Factor (0.8 - 0.99):

 

what size tankless water heater do i need?

Next, to determine the sizing of the tankless water heater, you must consider these big factors: 

1.Flow rate (GPM)

2.Temperature Rise

3.Heater Size Based on Flow Rate and Temperature Rise

Estimated Tankless Water Heater Sizes

Important Volumetric Inputs for kW Calculator:

1.Flow Rate (GPM):

• Gallons Per Minute (GPM): The amount of water to be heated by the heater in a minute.
• More power is needed at higher flow rates.

  Calculate Flow Rate (GPM)

  In short, flow rate signifies the rate of hot water consumed at any single time interval. Here is an example of how you would determine the flow rate based on fixed points such as appliances or fixtures: 
  
  
  
  
  

2.Temperature Rise (°F):

• The temperature difference between the desired water temperature & the incoming cold-water temperature.
• More power is required for a greater temperature increase.

3.Efficiency Factor:

• EUC is a measure of how great the water heater is at converting electrical energy into usable heat.
• Electric water heater common efficiency ranges are around 0.90 to 0.99.

Formula to Calculate Required kW:

The general formula is:

                                    kW=  Flow Rate (GPM)×Temperature Rise (°F)×8.33/ Efficiency     ​

• 8.33: The weight of a gallon of water in pounds.
• The numerator figures the energy needed to warm the water, and the denominator accounts for efficiencies that are lost.

Watts Calculator for Water Heater

The formula to calculate power, in watts, for a water heater is similar to the kW formula above but is multiplied by 1,000 to convert it to watts:

$$\text{ Watts}=\text{Flow Rate (GPM)}\times \text{Temperature Rise (°F)}\times 8.33\times 1,000/\text{Efficiency}$$

Uses of the Calculator:

1. Sizing Tankless Water Heaters – Helps you determine the proper power rating for a tankless water heater, based on the water you use in your home.

2. Energy Planning: Offers a realistic level of power demand, which can be used for energy consumption cost optimization.

3. HVAC Design: Assists engineers in designing water heating systems to be used in residential or commercial buildings.