Water Heater Recovery Calculator
Estimate gallons reheated per hour from heater input and efficiency.
Water Heater Recovery measurements
Enter your values, then calculate.
Result
How to calculate water heater recovery
This calculator finds water heater recovery rate — how much hot water a heater can produce per hour — from BTU input, efficiency, and desired temperature rise.
How the calculation works
Recovery rate (gallons/hour) = (BTU input × Efficiency ÷ 100) ÷ (8.33 × Temperature rise), where 8.33 is the weight of a gallon of water in pounds, used in the standard heat-to-water-volume conversion.
Example
40,000 BTU/hr input, 80% efficiency, 70°F temperature rise: (40,000×0.80)÷(8.33×70) = 32,000÷583.1 ≈ 54.9 gallons/hour.
Frequently asked questions
How is Result calculated?
Result = [Heater input] × ([Efficiency] ÷ 100) ÷ (8.33 × [Temperature rise]).
Is the Water Heater Recovery Calculator free to use?
Yes — every calculator on Simple Calculator Tools is free, runs in your browser, and does not require an account.
Water Heater Recovery Calculator
Recovery rate (gallons/hour) = (BTU input × Efficiency ÷ 100) ÷ (8.33 × Temperature rise), where 8.33 is the weight of a gallon of water in pounds, used in the standard heat-to-water-volume conversion.
Let's understand your water heater recovery result.
Calculate a result above and this guide will help you interpret it using this calculator's own formula and explanation.
Pro Tips for Water Heater Recovery
- Recovery rate is a key sizing factor for households with high hot water demand, since it determines how quickly a tank refills with hot water after heavy use.
- Higher desired temperature rise (colder incoming water requiring more heating) reduces recovery rate for the same BTU input and efficiency.
Common Water Heater Recovery Mistakes to Avoid
- Using a generic temperature rise assumption instead of the actual difference between your incoming water temperature and desired hot water temperature, which varies by season and location.
When to Use This Calculator
This calculator finds water heater recovery rate — how much hot water a heater can produce per hour — from BTU input, efficiency, and desired temperature rise.