Your Battery System
▾| Parameter | Value |
|---|---|
| Usable Capacity | — |
| Total Capacity | — |
| Battery Capacity (Ah) | — |
| System Voltage | — |
| Depth of Discharge | — |
| Battery Type | — |
Load-shedding runtime ladder
Calculate backup time to compare full, reduced, critical, and emergency load targets.
| Outage plan | Target load | Modeled runtime | Extra vs full |
|---|---|---|---|
| No runtime ladder calculated yet. | |||
Each row re-runs the protected engine at a lower wattage. It does not identify which appliances to switch off or check whether the inverter can handle startup surge.
No runtime plan calculated yet.
Power Backup Duration in Africa — Planning Your Energy Independence
With frequent power cuts across Africa, knowing your backup duration is essential. This calculator accounts for inverter efficiency (90%) and battery depth of discharge limits — the two factors most people ignore when sizing their backup systems, leading to shorter-than-expected runtime.
Disclaimer: Actual backup time depends on real load profile, temperature, and battery age. New batteries perform closest to these estimates.
Choose a wattage target, not a promised runtime
The runtime ladder keeps the battery assumptions fixed and shows what happens when the entered load falls to 75%, 50%, 40%, or 25%. Use each wattage as a target for a real appliance list.
- Count running watts: use nameplates or measured draw for devices that will operate at the same time.
- Check startup separately: a motor, pump, compressor, or fridge can exceed its running watts for a short period.
- Keep a reserve: battery age, heat, wiring, inverter idle draw, and cycling loads can reduce observed runtime.
Private by default. Battery and load inputs stay in this browser unless you choose to copy the outage plan.
Frequently Asked Questions
How is the load-shedding runtime ladder calculated?
The calculator re-runs the same protected runtime formula at 100%, 75%, 50%, 40%, and 25% of the entered load while keeping battery capacity, chemistry, depth of discharge, and 90% inverter efficiency unchanged.
What happens if I enter both kWh and Ah battery capacity?
The kWh input takes priority. Leave it blank if you want the calculator to convert amp-hours and system voltage into total kWh.
Why can real backup runtime be shorter than the estimate?
Battery age, temperature, wiring loss, inverter idle draw, startup surge, cycling loads, and lead-acid discharge behavior are not fully modeled. Measure real loads and verify battery and inverter specifications.
Validate backup runtime before relying on it
Estimate how long a battery or inverter setup may run essential loads, then compare usable capacity, loss, and battery chemistry.
Local-first estimate. No live quote or official approval is performed.
What to check
- Methodology: convert battery kWh or Ah/voltage into usable capacity, apply depth of discharge and inverter loss, then divide by load watts.
- Verify real load, surge demand, battery age, chemistry, temperature, inverter efficiency, wiring, ventilation, and critical-load priority.
- Copy the runtime brief before changing loads, buying batteries, or planning outage coverage.
Limitations
- Disclaimer: planning estimate only, not an emergency guarantee, installer quote, electrical certificate, warranty, or safety sign-off.
- Runtime can fall sharply with old batteries, high heat, overloaded inverters, poor wiring, and loads that cycle on and off.
- Source/reference note: verify against battery datasheets, inverter specs, installer guidance, and measured appliance draw.
Privacy note: the calculator runs in your browser. Do not paste account numbers, installer contracts, or private customer data into notes you plan to share.