At Yanmar, I coordinate emergency equipment fulfillment for construction and industrial customers. It was 4:47 PM on a Tuesday in March 2024. I was about to walk out of the office when my phone rang. A site supervisor I'd worked with for years didn't even say hello. He said, "Our backup generator just died, and the pour is Thursday morning. Can you help?" Actually, he said it a little less calmly than that.
He was working on a coal power production upgrade—new conveyor systems, environmental controls, the kind of project that has a regulator-approved deadline written in capital letters. The site office had grid power, but the concrete batching area was off-grid. That area needed a generator for the mixers, the conveyors, and overnight lighting.
Six months earlier, he'd bought a second hand generator from an online dealer. The listing said "fully refurbished, tested, ready to work." It wasn't. Under a real load, the alternator bearings failed. He'd asked me two weeks before the purchase if it was a good deal. I'd said I couldn't find a load test report, and that was a red flag. He saved about $4,000 by buying it anyway. I didn't say "I told you so." I didn't need to.
Some people in the industry think that if a project spec mentions Siemens turbine gas technology, the power problem is solved. Look—I'm not a gas turbine engineer. A Siemens turbine gas unit is an impressive piece of machinery for large, stationary power generation. But it is not the thing you call at 4:50 PM when a concrete pour is in 36 hours.
What he needed was a diesel generator. Specifically, one that could be load tested in our yard, put on a truck, and delivered before the pour. A Yanmar-powered 66 kVA unit was available. We had it in inventory, but only just. The next unit wasn't due back from a rental for another two weeks.
Here's the part that still frustrates me. The market for second hand diesel generators for sale is full of machines that look great in a photo and terrible in a load bank test. "Serviced" can mean someone changed the oil. "Low hours" can mean the hour meter was replaced. Unless you see the service records and a recent test under at least 80% load, you're buying a nameplate, not a generator.
When we got the failed unit back to our shop, we found mismatched hoses, a non-standard fuel pump, and a serial number that didn't line up with the engine. Honestly, I'm not sure why some used equipment dealers think they can hide that stuff. My best guess is they're betting on buyers not testing under load.
I've only worked with construction, industrial, and rental customers, so I can't speak to every sector. But in my experience—based on about 200 rush orders in the last six years—a used generator without documentation is a separate risk category, not a bargain.
Whenever I hear the phrase "fully refurbished," I still think about this client. He assumed that phrase meant the same thing to everyone. It doesn't.
The immediate problem wasn't just the generator. He also needed a small concrete mixer machine for a foundation slab on the other side of the site. His main mixer was tied up on another job. I sent him a rental quote within 20 minutes—one of our Yanmar-powered mixers, ready to go.
Then he asked about a cement brick making machine price. The project owner was thinking about making blocks on-site to avoid hauling them in. I told him to focus on the generator first. A cement brick making machine price is meaningless if you can't run the machine. Without reliable power, every number in the business case is a guess.
That's when I got into the habit of asking one question before anything else: "What's NOT included?" I've learned that question matters more than "What's the price?" A vendor who lists all fees upfront—even if the total looks higher—usually costs less in the end. Put another way: the cost of uncertainty is part of the price.
For the next 34 hours, our shop ran on this sequence: verify the generator's fuel system, change the oil and filters, run a load test, check the alternator output, check the coolant, then strap it to a lowbed. We finished the load test at 11 PM Wednesday. The truck left our yard at 3 AM Thursday.
For what it's worth, here's a rough reference point from the listings we tracked in January 2025: new 20–30 kW diesel generators from major manufacturers are typically listed between $8,000 and $15,000. Used units with similar claimed output range from $3,000 to $8,000. But a used unit without load test documentation is not "the same generator for less money"—it's a separate risk category. Based on publicly listed prices on major machinery marketplaces, January 2025. Prices vary by region and specification.
The generator arrived at 6:10 AM Thursday. The customer's crew had the connections ready. They started the unit, put it under load, and the pour began at 9 AM. It ran for 40 hours straight. The inspector signed off Friday evening.
The total cost was not the lowest quote on any list. It included the generator rental, the load test, the lowbed transport, the extra fuel filter kit, and a Saturday return pickup. But there was no hidden surprise at the gate. That was the point.
His alternative was renting from another local supplier. The supplier's base price was lower—about 20% lower—but they couldn't promise a delivery time before noon Thursday, and they wouldn't provide a load test certificate. Missing the pour would have triggered a penalty clause that was larger than the difference in cost. He told me later that the extra money felt like insurance, not waste.
Here's the lesson I keep coming back to. When you're under deadline, your worst enemy isn't a high price. It's a second hand generator with an invisible history. It's a plan that treats "estimated delivery" like "guaranteed delivery." And it's a purchasing process that optimizes the number on the invoice instead of the probability of the deadline being met.
I'm not saying new equipment is always the answer. A rental from a reputable dealer, a documented used unit, or even a well-specified gas turbine installation all have their place. A Siemens turbine gas package is right for some sites. This coal power production site wasn't one of them.
My experience is based on about 200 rush orders, mostly in construction and industrial power. If you're working on a ship or in mining, your travel times and risks are different. But the core question is the same: Can you prove this machine will work when it's needed? If not, the cheapest option becomes the most expensive one.
I do not mean that as a sales pitch. I mean it as a planner's rule.
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