Methods: Backup power size
electrify.backup-power.size · Version 0.1.0
Method
Battery usable kWh = critical energy over the outage, starting at the hour with the most critical load; nameplate = usable ÷ usable share. Generator kW = peak critical kW − the largest motor's running kW + its starting kW.
Assumptions
- Loads with no start time are spread evenly over the day for the battery, and counted at full kW for the generator.
- No inverter losses, battery aging, or temperature derating.
Sources
- NREL REopt, resilience analysis, REopt web tool, Critical load and outage duration inputs
Worked examples
| Example | Independent source | Tolerance | Last result |
|---|---|---|---|
| A refrigerator, a well pump, and lights through a 12-hour outage | electrify/backup-power spec, scenario "Load list": 4.8 + 3.0 + 1.8 kWh; the battery starts at 6 pm: 6 h × 0.625 kW + 6 h × 0.325 kW = 5.7 kWh | ±1e-9, ±1e-9, ±1e-9, ±1e-9, ±1e-9 | Not yet run in CI |
| A constant 5 kW through 12 hours | electrify/backup-power spec, scenario "12-hour target" | ±1e-9, ±1e-9 | Not yet run in CI |
| A 4.0 kW peak with a well pump that starts at 4.5 kW | electrify/backup-power spec, scenario "Motor start": 4.0 − 1.5 + 4.5 | ±1e-9, ±1e-9 | Not yet run in CI |
Known differences from reference engines
None recorded.
Cite this tool
Backup power size, version 0.1.0. gridprims. https://gridprims.com/tools/electrify/backup-power/size/