A 72-hour scenario tests battery size, occupant behaviour and charging opportunities. This is an assumed model, not a completed-project case.
Baseline scenario
Use the one-day Lab loads of 2.39 kWh per day. Assume unchanged use for three days, a full starting charge and no PV or generator input.
Reserve calculation
Required output energy is 2.39 × 3 = 7.17 kWh. With assumed efficiency 0.90 and usable fraction 0.80, nominal energy is 7.17/0.72 = 9.96 kWh before self-consumption and margins.
Sensitivity to use
An additional continuous 10 W over 72 hours adds 0.72 kWh at the output. Small continuous loads and inverter self-consumption therefore matter in extended outages.
Season and supplementary supply
Do not credit winter PV without a climate time series. A generator can change the balance but requires safe siting, fuel and compatible charging.
Limits and decisions
The model excludes heating, battery ageing, temperature limits and motor starts. Agree a load-reduction plan rather than assuming necessary systems can automatically be turned off.
| Item | Parameter | Check / result |
|---|---|---|
| Baseline | 2.39 × 3 | 7.17 kWh |
| Nominal | 7.17 ÷ 0.72 | 9.96 kWh |
| +10 W | 10 × 72 ÷ 1000 | +0.72 kWh |
What this means for your project
Test several starting charge levels and winter shortfalls. The calculator yields an energy budget; inverter, protection and controls require separate selection.
Sources and scope of review
- US DOE — Solar integration: energy and storage basics
- European Commission JRC — PVGIS
- CPSC — Generator and carbon monoxide hazards, 2026
Related reading
- Heat Pumps in Low-Energy Homes
- How to Size a Home Battery
- Solar PV in Winter: What to Expect
- ZeroHouse Lab: 24-Hour Backup Scenario