Three calculators. Zero internet required.

Generator runtime, vehicle range, and solar/battery autonomy — all three run entirely in this page's own JavaScript, so they work exactly the same offline from the vault as they do here. Nothing you enter is saved, stored, or sent anywhere; every number resets when you reload the page.

Generator Runtime

How long your stored fuel keeps a generator running, and how many days of supply that gives you.

Total fuel stored (gallons)

Consumption rate (gal/hr at your load)

Hours you plan to run it per day

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Consumption rate is on your generator's spec sheet, or estimate: small (2,000–3,500W) gas generators run roughly 0.3–0.6 gal/hr at 50% load; mid-size (5,000–7,500W) run roughly 0.6–1.1 gal/hr.

Vehicle Range

Total drivable distance on your tank, plus any fuel you have stored in cans.

Fuel tank capacity (gallons)

Fuel economy (MPG)

Extra fuel stored in cans (gallons, optional)

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Use real-world MPG, not the window-sticker number — it runs lower under load, in cold weather, or off-road.

Off-Grid Solar / Battery Autonomy

How many days a battery bank lasts on its own, and whether solar input keeps up with your daily load.

Battery capacity (Wh)

Daily load (Wh/day)

Solar panel output (W, optional)

Average usable sun hours/day (optional)

Enter your numbers above

Solar generation estimate applies a 0.75 system-loss factor for charge controller, wiring, and inverter inefficiency — a realistic number, not the panel's rated peak.

All three calculators use straightforward arithmetic, not simulation — verify anything safety-critical against your own equipment's documentation.

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