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Calorifier Recovery Time Calculator

Use this Calorifier Recovery Time Calculator to estimate how long a calorifier takes to reheat its stored volume, based on heater capacity, stored volume and the required temperature rise.

Input Parameters

Litres

°C

°C

kW

%

Calculation Results

Temperature Rise — °C
Energy Required — kWh
Recovery Time — Hours
Recovery Time — h : min

Calculation Formulas
  • ΔT = Storage Temperature − Cold Water Temperature
  • Energy = Volume × 4.186 × ΔT / 3600
  • Effective Heat Input = Heater Capacity × Efficiency
  • Recovery Time = Energy ÷ Effective Heat Input

The value 4.186 is the approximate specific heat capacity of water in kJ/kg·°C. Efficiency reduces the usable heat input (e.g. 90% = 0.90), which lengthens the recovery time.

How to Use This Calculator

  1. Enter the storage volume to be reheated.
  2. Enter the cold water and storage temperatures.
  3. Enter the installed heater capacity in kW.
  4. Enter the system efficiency.
  5. Review the estimated recovery time and download a PDF report.

Frequently Asked Questions

What is calorifier recovery time?
Recovery time is how long the calorifier takes to reheat its full stored volume from the cold water temperature up to the storage temperature.
How is recovery time calculated?
The energy needed to heat the stored volume is divided by the effective heat input (heater capacity adjusted for efficiency), giving the time in hours.
Why is a bigger heater faster?
A higher heating capacity delivers more energy per hour, so the same volume reaches temperature in less time.
Does efficiency affect recovery time?
Yes. Lower efficiency reduces the usable heat input, so the recovery time increases.
What is a typical recovery time?
It depends on the design intent, but many systems target one to two hours. Shorter recovery requires a larger heating capacity.

Results are estimates based on the values entered and the calculation method shown. Actual system requirements may vary depending on operating conditions, demand patterns, equipment configuration and applicable project requirements.