Charging battery storage with a petrol or diesel generator: which is the right choice?

Quick 30-second summary

• Petrol wins for most households: Petrol inverter generators are approx. 40% cheaper to buy, simpler to maintain and quieter in operation. For occasional power cuts, they are the best choice.
• Always go by rated power: When calculating and choosing a generator, we always use the rated (continuous) power, not the maximum, because only rated power guarantees safe, uninterrupted operation under load.
• Diesel is for professional use: Diesel models only start saving you fuel at several hundred operating hours a year. For several thousand hours a year, you need water-cooled diesel generators running at 1,500 rpm.
• LPG option: SPARK petrol inverters can run on LPG, which significantly lowers the cost of the energy generated and makes fuel storage simpler.
• Don’t calculate ROI when the power goes out: Backup power isn’t about economics – it’s about keeping your comfort: a warm home, a working fridge, the TV and an uninterrupted everyday life.

When you’re planning backup power for a solar battery storage system or a residential building, one key question comes up straight away: should you choose a petrol or a diesel generator?

On paper, the decision looks technical, but in practice buyers often overestimate the need for a diesel engine or overlook important details about maintenance, noise, type of power output and the initial investment. Let’s take a realistic look at both, based on our many years of experience selling and servicing SPARK generators.

Petrol vs. diesel: why is a petrol generator the better choice in 80% of cases?

If you’re buying a generator as a safety backup for occasional power cuts or to top up your battery storage during several days of bad weather, a petrol inverter generator is almost always the winner.

The main reasons are:

• Significantly lower purchase price: Petrol inverter generators are on average around 40% cheaper than comparable diesel models.
• Simpler, cheaper maintenance: Petrol engines have less complex injection systems and lower routine servicing costs.
• Quieter operation: Petrol inverters in a soundproof canopy run exceptionally quietly, which is crucial in residential neighbourhoods and densely built-up areas.

So when does a diesel generator pay off? The difference in fuel consumption with diesel only becomes noticeable once the generator runs for several hundred hours a year. If, however, you plan to use it for several thousand hours a year (e.g. continuous power supply for remote locations or industrial plants), conventional air-cooled engines are no longer enough – this is where heavy, water-cooled diesel engines come in, running at a low 1,500 rpm and built along the lines of rugged marine engines.

The hidden trap of old fuel: the problem with biodiesel in fuel tanks

A backup generator can stand on standby for months without being started even once. And this is where fuel becomes a problem – one that spares neither petrol nor diesel.

A story from the field: autonomy on an island and remote control

With modern SPARK generators, automation and ease of use are available on both petrol and diesel models.

What ROI? When the power goes out, only comfort matters!

Before buying, many customers get tangled up in complex calculations of return on investment (ROI) and fuel consumption per kWh of charged battery. But the reality in the field is completely different.

When a major power cut hits and the whole neighbourhood is stuck in the dark, all the economic calculations instantly evaporate. At that moment only one thing matters: that your comfort doesn’t suffer. That you can cook Sunday lunch for your guests without a hitch, watch the World Cup match on TV, keep the house pleasantly warm or cool, have hot water for a shower, cold beer in the fridge and the food in the freezer safe from thawing.

Comparison of recommended SPARK 2-Wire inverter generators with a canopy

For charging battery storage, we recommend only inverter models in a soundproof canopy that support 2-Wire automatic start and protect vital parts from the weather. When sizing, we always go by the generator’s rated power:

Frequently asked questions (FAQ)

1. Is a petrol generator harder to start in winter than a diesel one?

Quite the opposite. At sub-zero winter temperatures, petrol engines start much more easily than diesels, where unsuitable fuel can begin to separate out paraffin wax. SPARK inverter models also have an automatic choke for trouble-free winter starting.

2. How often do I need to change the fuel in a generator I’m not using?

We recommend refreshing the fuel in the tank at least once every 12 to 24 months. With diesel generators, always use a fuel stabiliser or periodically use up the fuel in other vehicles or machinery.

3. Why do all the recommended SPARK models include a soundproof canopy?

The canopy not only reduces noise by 5 to 10 dB(A) but also allows safe outdoor installation. It protects the alternator, electronics and battery from rain, snow, dirt and unauthorised access.

4. Are conventional AVR generators suitable for charging battery storage?

No, conventional AVR generators are not suitable for powering or charging battery storage and hybrid inverters. AVR regulation does not provide a sufficiently clean sine-wave voltage or a stable frequency when the load fluctuates. The hybrid inverter will therefore reject the voltage (flagging it as unstable), or the sensitive electronics may even be damaged. Inverter generators are a must for battery storage.

5. Can the generator be connected to gas (LPG)?

Yes, of course! The SPARK 6000iA, 13000iA and 15000iA models can be connected to LPG, which can lower your energy costs considerably. Besides the lower costs, another advantage of LPG is that it does not go stale or leave deposits in the carburettor, making starting even more reliable after long periods of disuse.

Still torn between a petrol and a diesel generator for your battery storage?

Don't guess on your own. Call our experts and, based on how you'll use it, your storage type and your location, we'll recommend the most economical and reliable solution.

Free consultation 01 23 50 202