How much fuel to store for generator use, how to store it safely, and how to calculate your reserve based on your power needs.
A generator is only as useful as the fuel you have stored for it. Understanding how much fuel your generator actually consumes, how long your stored fuel will last, how to store it safely, and how to extend it with load management turns a generator from a short-term solution into a meaningful emergency power resource.
Consumption depends on load (how much power you are drawing):
| Generator Size | At 50% Load | At 100% Load |
|---|---|---|
| 1000W inverter | ~0.5 L/hour | ~0.8 L/hour |
| 2000W inverter | ~0.8 L/hour | ~1.5 L/hour |
| 3500W conventional | ~1.5 L/hour | ~2.5 L/hour |
| 5000W conventional | ~2.0 L/hour | ~3.5 L/hour |
| 7500W conventional | ~3.0 L/hour | ~5.0 L/hour |
Diesel generators are generally 20–30% more fuel-efficient than petrol equivalents at the same wattage, making diesel preferable for extended use.
To estimate your daily fuel requirement:
Example: A 2000W inverter generator at 50% load (800W average) for 4 hours/day uses approximately 3.2 litres/day. A 30-litre supply covers roughly 9 days.
| Duration | Fuel Required (2000W generator, 4 hrs/day) |
|---|---|
| 3 days | ~10 litres |
| 7 days | ~22 litres |
| 14 days | ~45 litres |
| 30 days | ~95 litres |
For extended outages, 30 litres is a reasonable minimum to have on hand — extending to the legal limit of your jurisdiction if you need longer-term coverage.
Follow the same principles as general fuel storage:
Petrol/gasoline degrades in 30–60 days:
Even stabilised fuel should be used and replaced:
Running your generator at lower loads significantly reduces fuel consumption:
| Strategy | Fuel Impact |
|---|---|
| Run at 50% load instead of 100% | ~30–40% less fuel per hour |
| Use inverter generator (vs conventional) | 20–40% more efficient at low loads |
| Run in cycles (2 hrs on, 6 hrs off) | ~75% of continuous fuel use |
| Power only critical devices | Reduces load; reduces consumption |
| LED lighting instead of incandescent | Lighting load drops from ~300W to ~30W |
| Turn off heating elements (kettles, toasters, hair dryers) | These are disproportionate loads |
An intermittent operation cycle preserves fuel while maintaining function:
Morning cycle (2 hours):
Evening cycle (2 hours):
This approach uses approximately 1/3 of the fuel of continuous operation.
⚠️ Never refuel a running or hot generator. Petrol splashed on a hot engine will ignite instantly. Allow the engine to cool completely before adding fuel.
| Generator Size | Fuel Use at 50% Load | Days per 30L Stored (4 hrs/day) |
|---|---|---|
| 1000W inverter | ~0.5 L/hr | ~15 days |
| 2000W inverter | ~0.8 L/hr | ~9 days |
| 3500W conventional | ~1.5 L/hr | ~5 days |
| 5000W | ~2.0 L/hr | ~3.75 days |
| Storage | Approved containers; outdoors; cool; ventilated | |
| Stabiliser | Add when filling; label with date; use within 12 months | |
| Operation | Cycles not continuous; low load; critical devices only |
Take Generator Fuel Storage Guide with you — no internet needed when it matters most.
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