Hot Water Storage Recovery Calculator
A browser-only estimate for sensible heating of stored water. It treats water mass as approximately equal to litres and applies a fixed specific heat capacity.
A QUICK WALKTHROUGH
How to use this tool
- Enter stored water volume, starting and target temperatures, heater rating, and efficiency.
- Review the required recovery energy, estimated time, and effective input power.
- Use the estimate as a planning aid alongside the actual appliance and installation requirements.
Calculation model
Water mass is approximated as 1 kg per litre. Required energy = mass × 4.186 kJ/(kg·K) × temperature rise. Effective input power = rated heater power × efficiency; recovery time = required energy ÷ effective power.
Scope boundary
This is a simplified estimate. It does not model tank stratification, heat loss, heater cycling, flow effects, pressure, controls, or compliance requirements. Confirm the result with the appliance documentation and a qualified professional where required.
GOOD TO KNOW
Common questions
What does efficiency mean here?
Enter the fraction of rated electrical or fuel power that reaches the stored water, expressed as a percentage.
Does this account for standby losses?
No. The estimate assumes all effective power heats the water during recovery.
Are inputs uploaded?
No. The calculation runs locally in this browser.