Essential Guidelines for Purchasing Pre-Owned Generators

Opting for a large, industrial-sized pre-owned or low-hour used generator can bring a plethora of advantages, especially for companies, both small and large, seeking a cost-effective route to acquire high-quality industrial assets. This strategy often paves the way for significant savings without compromising performance or reliability. Yet, to ensure the most beneficial deal, it’s crucial to approach the purchase with a discerning eye, paying attention to several pivotal factors that could greatly influence your decision.


At the outset, identifying the appropriate generator size tailored to your specific power needs is fundamental. For guidance on this initial step, refer to our comprehensive article on selecting the right generator size.

Following this, a series of considerations come into play, including the generator’s age, operational hours, and history of use, the manufacturer’s track record and credibility, the maintenance history and current condition of the unit, performance under a load test, and the nature of the seller (broker vs. distributor). Additionally, the availability of a guarantee or limited warranty from the seller can significantly enhance the purchase’s value and security.

Buying a second-hand generator from a reputable seller not only guarantees quality but also provides access to valuable technical information and support. It’s always beneficial to opt for a generator with detailed maintenance records, as it provides insight into the unit’s reliability, performance history, and any prior issues that may have been addressed. Below are some essential guidelines for purchasing pre-owned generators to ensure a successful and cost-effective acquisition.

Evaluating Age, Operational Hours, and Application

When exploring the market for a dependable pre-owned generator, a critical initial step involves scrutinizing its chronological age, accumulated operational hours, and the context of its application. Equate the generator’s hour meter to a vehicle’s odometer, offering a tangible measure of its usage intensity.

Understanding whether the generator served as a primary power source, or was reserved for standby duties can also shed light on its potential wear and maintenance history. Units relegated to backup roles often exhibit lower wear, benefiting from more attentive upkeep. Yet, it’s essential to acknowledge instances where a generator’s past usage and precise age might remain elusive. In such scenarios, the seller’s integrity and their capacity to conduct thorough inspections, perform necessary adjustments, and ensure the generator’s optimal performance before resale become paramount. Trust in the seller’s expertise and reputation becomes your most reliable guide in navigating these uncertainties.

Prioritizing Manufacturer Credibility and History

When selecting a pre-owned generator, the significance of the manufacturer’s history and credibility cannot be overstated. Opting for a well-regarded brand is crucial, not merely for the sake of reliability but also for the assurance of quality and future support. This decision becomes particularly vital when the generator is expected to play a central role in supplying power, whether as a primary source or for emergency backup.

The make and model might seem secondary, but choosing a trusted manufacturer with a proven track record of durability underlines a strategic approach to buying used machinery. Companies like Caterpillar, Cummins, Detroit Diesel, Onan, Kohler, and John Deere, among others, stand out for their longstanding reputation in producing dependable equipment that, with proper maintenance, endures over time.

These brands not only guarantee resilience but also ensure the availability of parts and servicing, minimizing potential downtimes. Thus, investing in a generator from a reputable manufacturer is not necessarily about paying more upfront but about securing reliability and support for the long haul.

Maintenance and Rebuild Quality Assessment

Assessing the generator’s maintenance history and rebuild quality plays a pivotal role in understanding its condition and potential longevity. While detailed historical maintenance records may not always be available, evaluating the seller’s current knowledge and practices in maintaining diesel engines, power units, transfer switches, and generator ends can offer crucial insights.

Key questions about their maintenance protocols, including installation and de-installation processes, availability of dyno-testing equipment, and the competency of their technical staff, can reveal much about the generator’s upkeep. It’s particularly important to ascertain if the generator has been well-maintained or rebuilt by professionals, as this significantly impacts its operational lifespan. Generators that have merely changed hands without proper maintenance are likely to offer diminished reliability and performance.

Inspecting for Wear and Tear: A Thorough Visual Check

Visual Inspection Essentials

Initiate the evaluation process with a meticulous visual inspection. Given its mechanical nature, a generator is susceptible to wear and tear over time. Examine the generator’s mechanical parts for signs of wear, fatigue, cracks, or corrosion. Identifying any questionable components is crucial; such parts should be promptly replaced with those recommended by the manufacturer to ensure functionality and safety.

Non-Original Components and Their Implications

Encountering a generator with components (engine or generator end) from a different manufacturer than originally equipped can be an alarming sign. However, this should not automatically disqualify the unit. If these components were installed by a certified technician, subjected to extensive testing, and are covered under some form of guarantee by the seller, the generator could still be a viable option.

Replacing Bearings and Bushings

Unless already addressed by the seller, it’s advisable to replace all bearings and bushings, irrespective of their apparent condition or functionality. These components are exposed to intense stress during operation, making it challenging to assess their condition accurately without full replacement. For the sake of operational reliability and safety, updating these parts is highly recommended.

Electrical Integrity Check

Thoroughly examine the generator’s electrical windings and wiring harnesses for any signs of melting or damage. Look for cracks in the insulation or any breakdowns on the wire’s surface. Replace any components that do not meet current standards to ensure the generator’s safety and efficiency.

The Importance of a Load Test

Confirm that the generator has undergone a load test, a standard procedure among reputable dealers. This test assesses the generator’s electric power generation efficiency, its response to varying loads, and overall operational capacity. It is advisable to ensure this test has been conducted, potentially multiple times, to mitigate the risk of unforeseen power failures.

Purchasing from Reputable Sources

Consider the source of your prospective generator—opting for a generator listed by a broker or on an online marketplace might carry higher risks compared to purchasing from a recognised dealer or distributor. Specialized machinery such as industrial diesel generators requires knowledgeable maintenance and testing, which is best guaranteed by industry professionals.

Securing Guarantees and Limited Warranties

While the nature of purchasing second-hand equipment inherently limits warranty offerings, it is still crucial to secure some form of guarantee or limited warranty. Even a short-term coverage of 30 to 90 days can offer peace of mind, especially when dealing with sellers who have a professional approach to testing and maintaining their equipment.