Calculate how many BTU it takes to heat water from gallons or liters and a start and target temperature, or find the final temperature or heating time.
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BTU to Heat Water Formula
The following formula is used to calculate the BTUs required to heat a given amount of water by a certain temperature change.
Variables:
- BTUs is the amount of energy required in British Thermal Units
- G is the number of gallons of water
- ฮT is the temperature change in degrees Fahrenheit
- 8.34 is the number of BTUs required to raise one gallon of water by one degree Fahrenheit
To calculate the BTUs required to heat water, multiply the number of gallons by the temperature change and then by 8.34.
| Gallons (US) | Temperature Rise (ยฐF) | BTUs |
|---|---|---|
| 1 | 10 | 83.4 |
| 1 | 20 | 166.8 |
| 2 | 30 | 500.4 |
| 3 | 40 | 1,000.8 |
| 5 | 30 | 1,251.0 |
| 10 | 20 | 1,668.0 |
| 10 | 40 | 3,336.0 |
| 20 | 30 | 5,004.0 |
| 30 | 40 | 10,008.0 |
| 40 | 60 | 20,016.0 |
| 40 | 70 | 23,352.0 |
| 50 | 60 | 25,020.0 |
| 50 | 70 | 29,190.0 |
| 75 | 70 | 43,785.0 |
| 80 | 60 | 40,032.0 |
| 100 | 40 | 33,360.0 |
| 100 | 70 | 58,380.0 |
| 500 | 10 | 41,700.0 |
| 1,000 | 10 | 83,400.0 |
| 10,000 | 10 | 834,000.0 |
| * Rounded to 1 decimal. Assumes water at ~60ยฐF (ฯ โ 8.34 lb/gal, cp โ 1 Btu/lbยทยฐF). | ||
What is a BTU?
A British Thermal Unit (BTU) is a unit of heat energy. It is defined as the amount of heat required to raise the temperature of one pound of water by one degree Fahrenheit. BTUs are commonly used in the power, steam generation, heating, and air conditioning industries. Understanding BTUs is essential for calculating the energy required to heat or cool a given amount of water or air. On a gas water heater, an input rating in BTU/h tells you how much energy the burner uses per hour at its rated setting. Output in BTU/h measures how much heat reaches the water per hour.
How to Calculate BTUs to Heat Water?
The following steps outline how to calculate the BTUs required to heat water.
- First, determine the number of gallons of water (G).
- Next, determine the temperature change (ฮT) in degrees Fahrenheit.
- Next, use the formula BTUs = G * ฮT * 8.34 to calculate the BTUs required.
- Finally, calculate the BTUs required to heat the water.
- After inserting the values and calculating the result, check your answer with the calculator above.
Example Problem :
Use the following variables as an example problem to test your knowledge.
Number of gallons of water (G) = 10
Temperature change (ฮT) = 20ยฐF
