Guide · Generators
Petrol, diesel or LPG generator
A petrol generator is the cheapest and lightest, so it suits occasional use; a diesel generator costs more and is heavier, but is built for many running hours; an LPG (dual fuel) generator also runs on gas from a cylinder, which does not go stale in a tank, with about 10% less power on gas. Choose the fuel by how many hours a year the generator runs and how long the fuel sits unused.
- Occasional use
- petrol or LPG/petrol
- Many running hours
- diesel
- Power on LPG
- about 10% lower
- Prices in the guide
- October 2026
A quick comparison
| Petrol | Diesel | LPG/petrol (dual fuel) | |
|---|---|---|---|
| Generator price | lowest | highest | slightly higher than petrol |
| Weight | lower | higher | same as petrol |
| Running hours | occasional | many hours, long runs | occasional, standby |
| Fuel while idle | goes stale, loses properties | more stable, watch for water | gas in a cylinder does not go stale |
| Power | full | full | about 10% lower on gas |
Petrol generator
A petrol generator is a good choice when it runs a few dozen hours a year: power cuts, a holiday home, tools in the field. The engine is lighter and simple to maintain, and the generator is the cheapest per kW.
The weakness is the fuel. Petrol loses its properties over time, so a generator that sits for months can be hard to start and the carburettor can get dirty. If the generator will sit for a longer period, use fresh fuel or a stabiliser and start it up now and then.
Diesel generator
A diesel generator pays off when it runs many hours: a building site, a workshop, a site without mains power, or frequent and long power cuts. The engine is built for longer running, and diesel fuel is less flammable than petrol.
- Diesel is heavier and more expensive. The KS 6100HDE weighs 107 kg, while the petrol KS 7000E of the same output weighs 76.2 kg.
- Diesel models such as the KS 6100HDE and KS 6100IDE ATSR have a preheater for easier cold starting.
- A diesel engine does not like long running at very low load. If you will mostly load the generator lightly, choose a smaller model.
- In the tank and the jerrycan, watch for water from condensation, and replace the fuel filter as the manual says.
LPG or dual fuel generator
A dual fuel generator runs on petrol and on gas (LPG) from a cylinder. According to the product description, models such as the KS 2900G and KS 7000E G can be started and run directly on gas. Gas in a cylinder does not go stale like petrol, so LPG is a good choice for standby power when the generator sits for a long time.
- On gas the generator gives less power. In the specifications of our dual fuel inverters (for example the KS 3100iG S and KS 5500iEG S) the power on LPG is stated as about 10% lower than on petrol.
- For the KS 5500iEG S (5.5/5.0 kW on petrol) that means about 5.0/4.5 kW on gas.
- When calculating the power you need, use the power on gas.
- The gas cylinder should stand outdoors or in a ventilated space, never in a cellar, because gas is heavier than air.
Examples from our range, same output
All the models in the table are rated 5.5/5.0 kW. Prices are valid at the time of writing (October 2026), and the run time at 50% load is as per the specification.
| Model | Fuel | Weight | Tank, run time | Noise | Price |
|---|---|---|---|---|---|
| KS 7000E | petrol | 76.2 kg | 25 l, about 17 h | 70 dB | €1,031.25 |
| KS 7000E G | LPG/petrol | 77.2 kg | 25 l, about 17 h (petrol) | 70 dB | €1,121.25 |
| KS 5500iEG S | LPG/petrol, inverter | 52.5 kg | 13.5 l, about 8.4 h (petrol) | 66 dB | €1,650 |
| KS 6100HDE | diesel | 107 kg | 11 l, about 8.5 h | 71 dB | €1,475 |
| KS 6100IDE ATSR | diesel, inverter, ATS connection | 97 kg | 18 l, about 19 h | 72 dB | €2,180 |
For these models the difference in noise is small. The bigger differences are in weight and price: diesel costs about €440 more than the petrol KS 7000E, and LPG/petrol about €90 more.
How to decide
- Estimate the running hours per year. Many hours and long continuous running point to diesel.
- Estimate how long the fuel sits. If the generator waits for months for a power cut, LPG or dual fuel is more practical.
- Check where you will keep the fuel: a jerrycan of petrol, diesel or a gas cylinder, in line with the regulations on flammable liquids and gas.
- Calculate the power you need in the power calculator; for LPG subtract about 10%.
- If the generator needs to run on its own, look at models with electric start and ATS.
Frequently asked questions
Is a diesel or a petrol generator better?
For occasional use, petrol is cheaper and lighter. For many running hours and long continuous running, diesel is better.
How much power does a generator lose on gas?
According to the specifications of our dual fuel models, power on LPG is about 10% lower than on petrol. The KS 5500iEG S therefore gives about 4.5 kW rated on gas instead of 5.0 kW.
Can an LPG generator start directly on gas?
According to the product description, conventional dual fuel models such as the KS 2900G and KS 7000E G can start and run directly on LPG. For other models, check the product description or ask us.
How long can petrol sit in a generator?
Petrol loses its properties over time, so do not leave it in the generator for months without use. If the generator sits for a long time, use a stabiliser and start it now and then, or consider an LPG model.
Is a diesel generator noisier?
For the models in our range the difference is small: 70 dB for the petrol KS 7000E, 71 dB for the diesel KS 6100HDE. Compare the figure for the specific model.
Related
Not sure which fuel to choose?
Tell us how many hours a year the generator runs and where it will stand, and we will suggest a petrol, diesel or gas model.