Generator runtime calculator

Use this calculator when the starting question is available runtime: how long an entered fuel volume may support a generator load under an entered fuel-rate assumption. It is useful for backup records, temporary supply notes, day-tank checks and operating discussions where the fuel-rate basis is already known.

The result is a worksheet value. It does not model refuelling, fuel storage, generator product curves, fuel type, engine condition or load changes. It shows gross runtime, then subtracts an entered reserve runtime so the working runtime remains visible.

Generator Runtime Use Cases

A runtime record is strongest when it includes the fuel-rate source. A seven-hour value without a fuel-rate basis is hard to review; a record that says "120 L, 90% usable, 15 L/h, 1 h reserve" is much clearer.

Runtime Record Boundary

This boundary prevents a runtime estimate from being confused with a site operating plan. The arithmetic is useful only while the entered fuel and fuel-rate sources are visible.

Input Checklist

If the load basis changes, the fuel rate may change. A runtime record at 50% load should not be copied into a 95% load discussion unless the fuel-rate source supports it.

Review Workflow

1. Name the generator, tank, backup supply or operating scenario.
2. Enter the fuel capacity represented by the record.
3. Enter the usable fuel percentage.
4. Enter the fuel rate from a suitable source.
5. Enter reserve runtime as 0 if no reserve is being held aside.
6. Record the load percentage used by the fuel-rate source.
7. Read usable fuel before relying on runtime.
8. If working runtime is below one hour, check fuel capacity and reserve basis.
9. If load basis is high, confirm the fuel-rate source.
10. Keep refuelling, fuel storage and manufacturer limits outside this runtime-only estimate.

The workflow keeps gross runtime, reserve and working runtime separate. That separation is useful when the user needs a logistics note without pretending the calculator has reviewed the full operating plan.

Worked Records

Australian Context

Generator runtime records in Australia often support standby, temporary supply and backup power discussions for 230/400 V, 50 Hz installations. The runtime value may sit beside generator kVA, changeover, load sequence, fuel storage, authority or manufacturer review. This page owns only the fuel arithmetic.

Use current generator manufacturer instructions, local authority expectations, site fuel-storage rules and project requirements when the runtime record becomes part of an operating or equipment decision. Keep the calculator output as a traceable worksheet.

Stop Points

• Fuel-rate source is missing or belongs to a different load condition.
• Usable fuel fraction is guessed without project or operating basis.
• Reserve runtime is being treated as an emergency procedure.
• Runtime is being used to decide refuelling or site fuel storage without separate review.
• Manufacturer, authority or project requirements provide a different basis.