Cold wave and tornado exposure create a dual-season risk pattern despite the lower federal declaration count.
Cold-Wave and Tornado Reliability
Illinois faces its most severe grid disruptions not from hurricanes or ice but from derechos, fast-moving windstorms that can match hurricane-force intensity with almost no advance warning. Commonwealth Edison, the dominant utility in northern Illinois, serves more than four million customers across the region, covering roughly 70 percent of the state's population.
In August 2020, a derecho tore across the Midwest with wind gusts exceeding 80 miles per hour. At its peak, more than 800,000 ComEd customers lost power. The storm damaged substations and transmission towers in addition to the typical overhead line and pole failures. ComEd described portions of the restoration as a grid rebuild rather than a simple repair job, and full restoration took six days. The south suburbs of Chicago were hit hardest, with communities like Harvey seeing more than 90 percent of customers without service for days.
For backup sizing, the derecho pattern matters because it combines the destructive force of a hurricane with the footprint of a regional thunderstorm. Damage spreads across a wide corridor, stretching mutual aid resources thin and extending restoration timelines beyond what a typical summer storm would require.
Federal disaster declaration for severe flooding in central and southern Illinois.
Source: FEMA DR-4728The gap between high NRI modeling (90.4) and low declaration count (7) suggests local events that may not reach the federal threshold.
Treat winter duration as primary, then validate summer storm flexibility.
Circulation fan, communications, and medical support during a winter outage.
Load
214W
Target
24h
Minimum
8,500 Wh
Fan is for air circulation, not heating — power stations cannot safely run resistive heaters.
Size this scenario in calculatorAdd refrigeration to preserve food during a multi-day grid outage.
Load
421W
Target
48h
Minimum
33,300 Wh
Consider expandable systems or solar for events beyond 48 hours.
Size this scenario in calculatorCritical Note: No single portable power station in our database covers the full 24-hour baseline at this load (6,144 Wh max). Use solar recharge, load rotation, or expandable systems for longer events.
Planning for brief outages only, despite cold-wave events requiring longer essential coverage.
Forgetting communications and medical-device continuity during winter interruptions.
Not accounting for heating-support blower surge behavior during startup.
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Composite score: 90.4 / 100
Rating: Very High
Top modeled hazards: Cold Wave, Tornado, Heat Wave
Hurricane score: 35.4
Winter Weather score: 84.3
Wildfire score: 37.4
Total (2014-2023): 7
Most recent: 2023-11-20 Flood
| Type | Count |
|---|---|
| Flood | 3 |
| Biological | 2 |
| Severe Storm | 1 |
| Tornado | 1 |
Required Wh = (Total Load W × Target Hours / Inverter Derate) × Safety Factor
Inverter derate: 0.70 (30% real-world loss)
Safety factor: 1.15
Rounding: Up to nearest 100 Wh
Illinois has an NRI composite risk score of 90.4 (Very High), with 7 federal declarations from 2014 to 2023. The gap between high NRI modeling (90.4) and low declaration count (7) suggests local events that may not reach the federal threshold.
For the primary scenario on this page (24-hour winter essential), the estimated minimum is 8,500 Wh for a 24-hour target. Refine this in the calculator with your actual devices.
NRI is a modeled risk index based on hazard exposure, vulnerability, and expected loss. FEMA declarations reflect federally declared incidents. They answer different questions — use both signals together for planning.
Sizing around nameplate watts without translating that into usable runtime under inverter losses. See the common mistakes section above for more state-specific pitfalls.
