raatools/

🏠 Homelab

Akkulaufzeit, Solardimensionierung, Stromverbrauch und Docker-RAM-Rechner für Self-Hosting-Setups

Sizing tools for self-hosted infrastructure — the calculations that decide whether a build actually survives contact with reality. How long a battery holds a server up, how much solar you need to run one continuously, what a rack draws from the wall, and how much RAM to give a stack of containers.

These came out of building the things they describe. The numbers they produce are the ones worth checking before you buy hardware, because the failure mode of guessing is either an expensive over-build or a server that dies every time the sun goes behind a cloud.

Which tool do I want?

If you…Use
You want to know how long a UPS or battery lastsAkkulaufzeit
You are planning an off-grid or solar-backed setupSolarpanel-Dimensionierung
You need total draw and running cost for a rackStromverbrauch
You are deciding how much RAM a container stack needsDocker RAM Planer

Battery capacity is not the number on the label

A 100 Ah lead-acid battery does not give you 100 Ah. Discharging lead-acid below about 50% wrecks its cycle life, so the usable figure is nearer 50 Ah, and that is before inverter losses of 10–15% and the capacity that Peukert's law eats at higher discharge rates. A rule of thumb that has never let me down: take the label figure, halve it for lead-acid, then remove another 15%.

LiFePO4 changes the arithmetic. You can take it down to 20% without meaningful damage, and it holds voltage far more steadily as it drains, so the usable fraction is more like 80%. It costs more per nominal amp-hour and less per usable one, which is the comparison that actually matters.

The other number people miss is idle draw. An inverter running with no load still burns 10–20 W, which is around 0.4 kWh a day doing nothing at all. On a small off-grid system that overhead can exceed what the server itself uses.