📖 Overview
This calculator estimates how long backup power will last and flags food safety risk windows.
It helps households plan refueling and refrigeration strategy during outages.
🧪 Example Scenarios
Use these default and higher-pressure example inputs to explore how sensitive this calculator is before using your real numbers.
| Input | Base Case | Higher Pressure Case |
|---|---|---|
| Generator Rated Wattage (W) | 5,000 | 6,000 |
| Average Load Percentage (%) | 42 | 50.4 |
| Gallons Of Gas Available | 18 | 20.7 |
| Fuel Burn At 50 Percent Load (gal per hour) | 0.62 | 0.74 |
| Safety Reserve (%) | 10 | 12 |
⚙️ How It Works
Estimates backup generator runtime from fuel burn behavior at load, then projects refrigeration safety window.
The Formula
Runtime = Usable Fuel ÷ Adjusted Burn Rate
| Generator Wattage | Rated running power output |
| Load % | Average electrical load percentage |
| Fuel Available | Total available gasoline volume |
| Burn @ 50% | Known generator burn rate at half load |
| Reserve % | Fuel reserve held back for contingencies |
💡This calculator is scenario-based. Better input quality leads to better decision quality.
⚠️This is a planning estimate. Real runtime changes with temperature load swings and generator maintenance condition.
Quick Reference
| Usable Fuel | Burn Rate | Runtime | Fridge Safety Window |
|---|---|---|---|
| 10 gal | 0.5 gal/h | 20 h | ~24 h |
| 15 gal | 0.7 gal/h | 21.4 h | ~25.4 h |
| 20 gal | 0.9 gal/h | 22.2 h | ~26.2 h |
When To Use This
- Use this tool when you need a fast decision during active planning or execution.
- Use this before committing money, time, or tradeoffs that are hard to reverse.
- Use this to compare options using the same assumptions across scenarios.
Edge Cases To Watch
- Results can be misleading if key inputs are missing, stale, or unrealistic.
- Very small or very large values may amplify rounding effects and interpretation risk.
- If assumptions change mid-decision, recalculate before acting.
Practical Tips
💡 Measure real average load with a meter when possible.
💡 Avoid running unnecessary appliances during outage windows.
💡 Plan refueling cadence before nighttime and bad weather periods.
Frequently Asked Questions
❓ Why add safety reserve?
A reserve protects against startup failures and unexpected load increases.
❓ Is refrigerator safety always runtime plus four hours?
It is a rough planning assumption and varies with fridge insulation and opening frequency.