Water Heater Recovery Time Calculator
How long a geyser/tank heater takes to reheat after a draw.
A 25 L geyser on a 2 kW element needs ~37 minutes for a 35 °C lift — why the second shower runs cold. Bigger element ≠ more hot water, just faster recovery.
Formula
Water Heater Recovery Time Calculator is a free geyser heating time for HVAC designers, technicians and energy auditors — instant, accurate and 100% client-side, with the governing formula and reference shown next to the result so the number can be defended, not just quoted.
About Water Heater Recovery Time Calculator
How long a geyser/tank heater takes to reheat after a draw. The calculation implements t = m·c_p·ΔT/(P·η) (Heater energy balance; IS 2082). A 25 L geyser on a 2 kW element needs ~37 minutes for a 35 °C lift — why the second shower runs cold. Bigger element ≠ more hot water, just faster recovery.
How to use Water Heater Recovery Time Calculator
- 1Enter Tank volume in L.
- 2Enter Temperature rise needed in °C.
- 3Enter Element power in kW.
- 4Enter Efficiency in %.
- 5Read Recovery time, Energy used instantly — no submit button needed.
- 6Need US units? Flip the SI/Imperial toggle and every field converts.
Why use Water Heater Recovery Time Calculator?
- ✓Implements the standard formula — t = m·c_p·ΔT/(P·η)
- ✓Reference cited on-page: Heater energy balance; IS 2082
- ✓One-click SI ⇄ Imperial toggle — values convert in place, physics stays in SI
- ✓Live worked example: the substitution recomputes from your numbers
- ✓Runs entirely in your browser — nothing uploaded, free forever
Frequently asked questions
What formula does the Water Heater Recovery Time Calculator use?+
It computes t = m·c_p·ΔT/(P·η), per Heater energy balance; IS 2082. The formula is displayed under the result along with a worked example substituted with your own inputs.
What should I keep in mind when using this calculator?+
A 25 L geyser on a 2 kW element needs ~37 minutes for a 35 °C lift — why the second shower runs cold. Bigger element ≠ more hot water, just faster recovery.
Is this based on ASHRAE methods?+
The calculations follow the standard ASHRAE/ISHRAE formulations cited under the result, simplified where industry practice does the same. For permit-grade design, confirm with the full code procedure.
Is the Water Heater Recovery Time Calculator free to use?+
Yes — completely free, no sign-up, no limits. It runs client-side in your browser, so inputs stay private and results are instant even on slow connections.
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