How to avoid underloading your generator

One of the most overlooked, yet potentially damaging, mistakes people make is running their generator at less than full capacity. Known as underloading, this issue can quietly reduce your generator’s efficiency, increase wear and tear, and shorten its operational life. In this blog, we’ll explain what underloading is, why it’s bad for your generator, and how you can prevent it.

What Is Underloading?

Underloading happens when a generator operates with too little demand placed on it – typically below 30% of its rated capacity. Instead of producing the level of power it was designed for, the generator runs lightly, often for extended periods. This might not sound like a big deal, but it can cause significant long-term damage.

You might have heard the term “wet stacking” before; that’s another name for this same issue. When a generator isn’t working hard enough, unburnt fuel and carbon particles build up inside the engine and exhaust system. Over time, this can lead to serious performance problems.

Why Underloading Should Be Avoided

Running your generator underload prevents it from reaching its optimal operating temperature. This leads to poor combustion and a range of mechanical issues that gradually impact performance.

One of the most common consequences is the build-up of carbon deposits and soot inside the engine. This happens because the fuel isn’t being burned off efficiently and instead settles in the exhaust system, cylinders, and turbocharger.

A more serious outcome is cylinder glazing. This occurs when unburnt fuel creates a sticky, varnish-like coating on the cylinder walls. If left unchecked, this coating hardens into a ceramic-like substance that reduces compression, increases oil consumption, and severely damages the engine over time. Once glazing sets in, repair costs can quickly escalate and the generator’s lifespan may be drastically reduced.

Additionally, underloading can lead to poor fuel economy, higher emissions, and reduced reliability during peak demand periods. In short, it’s bad for performance, bad for efficiency, and bad for your bottom line.

How to Prevent Underloading

The most effective way to avoid underloading is by ensuring you choose a generator that matches your actual power requirements. Bigger isn’t always better-opting for a generator with a much higher kVA than necessary will increase the risk of underloading.

Ideally, your diesel generator should run between 70% and 100% of its rated capacity during regular use. This load range ensures proper engine temperature is maintained, allowing for efficient combustion and minimal build-up of deposits.

If your application varies and you’re not always able to reach this optimal load, incorporating a load bank into your routine testing schedule can help. A load bank allows you to artificially simulate electrical demand, ensuring the generator is occasionally run at higher loads to burn off any built-up residue.

Regular maintenance is also essential. Scheduled servicing, load tests, and inspections can help spot early signs of underloading and prevent small issues from becoming expensive problems. If you’re unsure whether your generator is operating efficiently, our team can carry out a full assessment and offer practical solutions.

Get Expert Advice Today

At CPS, we specialise in designing and manufacturing bespoke diesel generators that are tailored to your specific requirements. Whether you need a generator for continuous use, standby backup, or prime power applications, we work closely with you to ensure your equipment is the right size and specification from day one.

If you’re unsure whether your current generator is the right fit for your needs, or if you’ve noticed signs of underloading, don’t wait for problems to arise. Get in touch with the CPS team today for tailored advice and support.

We’re here to help with generator sizing, load testing, and ongoing maintenance, ensuring your investment performs at its best for years to come.