Generator Running Cost Calculator
Generator running cost calculator estimates fuel expenses per hour, day, and month. Calculate how much it costs to run a portable or standby generator based on consumption rate, fuel price, and hours of operation.
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Formula
Multiplies the generator fuel consumption rate by the number of hours and the cost per litre to find total fuel expenditure. Small portable generators use 0.5 to 1 L/hr while large standby units consume 3 to 10 L/hr.
Worked Example
Understanding Generator Running Costs
- Small portable generators (1-3 kW) consume 0.5 to 1 L/hr, costing $0.75 to $1.50/hr
- Medium residential generators (5-8 kW) use 1.5 to 3 L/hr, costing $2.25 to $4.50/hr
- Large standby generators (10-20 kW) consume 3 to 10 L/hr, costing $4.50 to $15.00/hr
- Running a mid-size generator 6 hours daily costs roughly $675/month at $1.50/L fuel
- Generator power costs 3 to 5 times more per kWh than grid electricity
Minimize generator costs by running only essential loads, maintaining proper servicing schedules, and using the right size generator for your needs. An oversized generator wastes fuel, while an undersized one runs at harmful high loads.
You can also calculate changes using our Fuel Cost Increase Calculator or Fleet Fuel Expense Calculator.
Frequently Asked Questions
How do I find my generator's fuel consumption rate?
Check the manufacturer specification sheet. It is usually listed as litres per hour at a given load percentage, typically 50% or 75% load. A common 5 kW portable generator uses about 1.5 to 2.5 L/hr at 75% load.
Does load percentage affect fuel consumption?
Yes, significantly. Running at 50% load uses roughly 30-40% less fuel than 100% load. A generator rated at 3 L/hr at full load might use only 1.8 to 2.0 L/hr at half load.
How much does a generator cost per hour to run?
It depends on size and fuel price. A small portable unit (0.5 to 1 L/hr) costs $0.75 to $1.50/hr at $1.50/L fuel. A mid-size residential unit (2.5 L/hr) costs about $3.75/hr. Large standby generators (5 to 10 L/hr) cost $7.50 to $15.00/hr.
Is running a generator cheaper than grid power?
Almost never. Generator power costs $0.30 to $0.80 per kWh compared to grid electricity at $0.10 to $0.25 per kWh. Generators are 3 to 5 times more expensive and should be used as backup, not primary power.
How much does it cost to run a generator for a month?
For a mid-size generator using 2.5 L/hr running 6 hours daily at $1.50/L fuel, monthly cost is $675. Running it 12 hours daily doubles that to $1,350/month. Reducing usage hours is the most effective way to lower costs.
What is cheaper for generators, diesel or petrol?
Diesel generators are typically 15-20% more fuel-efficient than petrol generators of the same size. However, diesel fuel may cost slightly more per litre. For extended daily use (6+ hours), diesel generators usually offer lower running costs overall.
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