How many btu's would it take to heat 120 gallons of water to 210 degrees f in 2 hours?

To calculate the BTUs required to heat 120 gallons of water to 210°F, first determine the temperature rise needed. Assuming the initial water temperature is around 60°F, you would need to raise it 150°F (210°F - 60°F). The BTU calculation is:

[ \text{BTUs} = \text{gallons} \times \text{temperature rise} \times 8.34 ]

So,

[ \text{BTUs} = 120 \text{ gallons} \times 150°F \times 8.34 \approx 1,500,600 \text{ BTUs}. ]

To heat this in 2 hours, you would need about 750,300 BTUs per hour.