Prime versus standby rating, real running hours, load bank testing and emissions: what to check before you buy a used diesel genset.
MAKINTER brokers the sale and purchase of used generator sets and power generation equipment. These assets move around a lot: construction sites that finish, plants that change their supply contract, rental companies renewing their fleet. That keeps supply steady, and it is also why they need to be looked at carefully.
Here we explain what we cover, the rating difference that causes the most misunderstandings, and what to check before you pay. If you are after something specific, browse the available inventory or ask us to source it.
This is the most expensive confusion in the category. ISO 8528-1 distinguishes several ratings: emergency standby power (ESP) is valid only for backup supply at variable load and a limited number of hours per year; prime power (PRP) allows continuous operation at variable load; and continuous power (COP) is what can be sustained indefinitely at constant load.
The big figure in the advert is almost always the standby rating. If your use is continuous, the machine you actually need is considerably larger than that number suggests. Before you compare prices, make every offer quote the same rating.
Watch the expected load factor too. A diesel running for long periods well below its rated load suffers carbon build-up and premature wear. Oversizing by too much also costs money.
The hour meter is the most frequently tampered-with figure. Cross-check it against what can be seen: maintenance reports, controller logs, parts invoices, the condition of hoses and wiring, and whether the visible wear is consistent with the declared hours. A unit with 2,000 declared hours and a clearly aged engine bay needs explaining.
On the engine, what matters: oil and coolant leaks, smoke on start-up and under load, play, turbo condition, compression where it can be measured, and oil analysis. On the alternator: insulation resistance testing, bearing condition, clean windings and no moisture. On the panel: make and model of the controller, whether support and spares are still available, and whether the settings have been preserved.
A set that starts and sounds healthy off-load proves almost nothing. The test that counts is on a load bank: load steps, voltage and frequency measured at each step, governor behaviour, stabilised temperatures and fuel consumption. If the seller cannot or will not run one, that is information in itself, and it should show in the price.
Engines placed new on the European Union market must meet the emissions stage in force at the time they are placed on the market. A second-hand set built under an earlier stage can still be used, but some countries, cities and public tenders restrict the use of older-stage engines, and fixed installations may be subject to their own requirements.
Before buying for export, confirm what the destination country requires: accepted emissions stage, type approvals, fuel tank and spill containment requirements, and noise limits. It is a cheap check that avoids buying equipment you then cannot install.
Confirm the output voltage and frequency and whether the alternator is reconnectable. Going from 50 to 60 Hz is not always feasible or free: it changes the available output and may require work on the governor and the engine. Check the earthing arrangement as well, and whether the unit includes the ATS and protections you will need, because adding them later usually costs more than negotiating them into the package.
A containerised or skid-mounted set is one of the easier assets to move: it travels in one piece, with lifting points designed in and predictable dimensions. Even so, the fuel has to be drained, the unit secured to the trailer, and the sheer weight allowed for, which on large sets means abnormal load transport.
Our guide to transport costs breaks down what you actually pay and how to ask for a comparable quotation.
We are an independent broker: we are neither the owner of the equipment nor the installer. We prepare the technical listing from what the seller provides, cross-check what can be verified, and present it to qualified buyers. When there is real interest, we coordinate the visit, the load test and the transport.
There is no upfront cost for the seller: commission is charged only if the deal closes. The other common questions are answered in our FAQ, and the general buying criteria in our buying guide.
Tell us the output you need, the duty cycle and the country of installation and we will source the unit: find an asset. If you have idle sets you want to sell, tell us what you have. For anything else, write to us.
The information on this page is general and for guidance only. The specific conditions of each unit are set out in its listing and in the offer issued.