How Much Would It Cost to Run a Generator 24 Hours a Day?
Running a generator 24 hours a day costs about $17 to $256 in fuel across the units we stock, at early September 2026 prices. Load decides where you land. Here's the working for a light, half and heavy day.
Generator Running Costs per 24 Hours
How the Numbers Are Worked Out
Each figure starts with the maker's own run time. Divide the litres a generator holds by the hours it lasts at the tested load and you've got litres an hour. Multiply by 24, then by the price of a litre.
Prices are the ACCC's early September 2026 averages for the five largest cities: $2.05 a litre for petrol and $2.49 for diesel. They're the same prices our generator fuel consumption guide uses, and that guide has the burn rate for every stocked unit. This page goes deeper on the full day.
All costs here are fuel only.
| Load | Generator | Fuel | Litres per hour | Litres per 24 hours | Fuel per 24 hours | Tank fills per 24 hours |
|---|---|---|---|---|---|---|
| Light (25%) | Champion 2.5kVA inverter | Petrol | 0.35 | 8.3 | $17.11 | 2.1 |
| Light (25%) | Westinghouse iGen4500AS | Petrol | 0.76 | 18.2 | $37.31 | 1.3 |
| Half (50%) | Hyundai HY3500i | Petrol | 1.09 | 26.2 | $53.67 | 4.4 |
| Half (50%) | Hyundai DHY6000SE | Diesel | 1.00 | 24.0 | $59.76 | 1.5 |
| Half (50%) | Westinghouse WHXC8500E | Petrol | 1.91 | 45.8 | $93.89 | 1.8 |
| Heavy (80%) | Gentech ED7000LSRE | Diesel | 1.70 | 40.8 | $101.63 | 8.2 |
| Heavy (75%) | Hyundai DHY8700SE-LRS | Diesel | 1.89 | 45.3 | $112.88 | 2.7 |
| Heavy (80%) | Gentech EP7000HSR | Petrol | 2.44 | 58.6 | $120.05 | 9.6 |
| Heavy (80%) | Gentech ED8500KSRE | Diesel | 2.62 | 62.8 | $156.30 | 1.8 |
The top of the range, $256.11, is the Hyundai DHY12000XSEM-RS 10kVA diesel flat out at 100%.
Three Worked Examples
Light Load Day (About 25%)
A fridge, lights, the telly and phone chargers barely trouble a 2.5kVA inverter. The Champion 2.5kVA burns about 8.3 litres over 24 hours at quarter load, which is $17.11 in petrol. Its 4 litre tank needs filling about twice.
Put the Westinghouse iGen4500AS on the same kind of day and it's $37.31. It's also carrying about twice the load at its own quarter mark, and its 13.5 litre tank covers the day with one top-up.
Half Load Day (About 50%)
This is a proper blackout day: fridge, freezer, lights, the water pump and the kettle going on and off. At half load the Hyundai HY3500i costs $53.67 in petrol, but its 6 litre tank wants filling more than four times.
The Hyundai DHY6000SE diesel costs $59.76 for the same 24 hours. That's about $6 more while it carries around 2,350W against the HY3500i's 1,500W, and its 16 litre tank needs one and a half fills.
The Westinghouse WHXC8500E at half load is a bigger house day, about 3,400W, for $93.89 from under two fills of its 25 litre tank.
Heavy Load Day (75% to 80%)
Run a site generator hard around the clock and the bill climbs. The Gentech EP7000HSR petrol burns 2.44 litres an hour at 80% load, which is $120.05 over 24 hours. The Gentech ED7000LSRE diesel, at the same 7kVA rating and test load, comes in at $101.63.
The Hyundai DHY8700SE-LRS diesel costs $112.88 for the day at 75%, and the Gentech ED8500KSRE costs $156.30 at 80%.
Petrol vs Diesel Over a Full Day
The 7kVA Pair at 80% Load
On that Gentech pair, diesel saves about $18 a day at 80% load. The diesel also costs $2,570 more to buy, $4,959 against $2,389. At that rate it takes about 140 days of round-the-clock running to pay the difference back.
So diesel earns its keep on long, steady runs, not a few blackouts a year. Our petrol vs diesel generator guide weighs it up properly.
Diesel on Light Loads
Don't buy a big diesel to loaf through light days. Caterpillar's paper on generator set underloading says running a diesel below 30 percent of rated output for extended periods leads to wet stacking, also called exhaust slobber. For a light 24-hour day, a petrol inverter usually makes more sense.
Costs Beyond Fuel
Refills and Jerry Cans
The tank fills column matters as much as the dollars. The ED7000LSRE's 5 litre tank needs filling more than eight times a day at 80%, and the EP7000HSR's 6.1 litres more than nine. Each of those is a stop, because Westinghouse's instruction manual says to turn the engine off and let the generator cool before refuelling.
Oil Changes on Continuous Runs
Running 24 hours a day chews through service intervals. The maintenance schedule in that same manual has the oil checked before every use, changed after the first 20 hours, then changed every 100 hours or six months.
At 24 hours a day, 100 hours comes around every four days or so. A week of running means at least one oil change on top of the fuel, with the level checked while it's stopped for fuel. There's more on long runs in can a portable generator run 24 hours a day.
Cutting the Daily Bill
Most people don't need the full 24 hours. Energex suggests turning the generator off at night and when you're away, and notes that refrigerators may need to run for only a few hours per day to preserve food.
Run the fridge and freezer in blocks, then shut it down. Halve the hours and you roughly halve the fuel bill in the table.
So how much would it cost to run a generator 24 hours a day? About $17 on a small inverter doing light work, $54 to $94 for a typical blackout day, and $100 to $156 on a 7kVA to 8.5kVA unit working hard.
Want the numbers for your own loads? Ring the store on 03 7056 6732, SMS 0476 330 590, or try the generator finder.
