Heat loss & emitters
Buffer energy-storage estimate
- where
- buffer volume (m³; the calculator shows L)
- excess heat above current load (W; any unit you pick is converted)
- desired storage duration (s; any unit you pick is converted)
- fluid density (kg/m³)
- specific heat capacity (J/(kg·K); any unit you pick is converted)
- usable buffer temperature swing (K)
Explain this equation
Estimates the volume of water needed to store surplus heat for a set time within a given temperature swing. Use it as a first estimate when considering a buffer tank.
P is the surplus heat above the current load. t is how long you want to absorb it. ρ and c_p describe how much heat each cubic metre of water stores per degree. ΔT is the usable temperature swing in the buffer.
P × t is the surplus energy. Each cubic metre stores ρ × c_p × ΔT, so dividing gives the volume. The calculator works in m³ and shows litres.
Sense check: 5 kW for 10 minutes with a 5 K swing needs about 144 L. Double the swing and the volume halves.
Watch out: this does not set heat-pump minimum volume, defrost needs or anti-cycling compliance. Check manufacturer requirements.
Enter your values to see the result.
Good to know
Subtract only genuinely usable existing system volume in a justified design. This does not establish heat-pump minimum volume, defrost needs or anti-cycling compliance.
Sources
Results are arithmetic only. Worked examples are not recommended design settings. This library does not provide automatic gas pipe selection, live gas tightness tests, purging procedures, combustion acceptance limits, installation approval or commissioning certification. Manufacturer data and the applicable current method remain essential.