SDMO Generator Buying Checklist: 7 Spec Checks Before You Order

This is for anyone about to order an SDMO generator—or any industrial diesel genset, honestly. Facility managers, contractors, procurement teams. If the spec sheet hasn't been written yet, this checklist will help you write it. If it has, it'll show you what's likely wrong with it.

I'm the quality and compliance manager at an industrial power generation company. Every genset proposal crosses my desk before it reaches customers—roughly 200 spec sheets a year. I've rejected 9% of first deliveries in 2024 for spec mismatches, and nearly all of them trace back to the ordering stage, not the factory. So glad we formalized a verification protocol in 2022—before that, "review" meant a skim and a hopeful signature.

Here are the 7 checks I run. Takes about 15 minutes.

Step 1: Set the Load on Paper, Not on Feelings

Start with the load plan. Not the brochure, not the budget—the actual electrical load. Three things I verify:

• kW or kVA? Mixing these two is how gensets get undersized. Most ratings are quoted in kVA at a 0.8 power factor. An 800 kW SDMO generator is typically the same machine as a 1000 kVA SDMO generator.
• Starting loads. Motors draw 5-7 times their running current on startup. A single 200 kW motor on a 550 kW SDMO diesel generator can cause a voltage dip the whole site will feel.
• Future load. Size too tight and you'll pay for a re-cable in three years. Size too loose and you're burning fuel in an oversized engine. I've seen both.

Example: a customer picked an 800 kW SDMO generator because "800 is bigger than 700." Actual demand was 480 kVA with a 620 kVA peak. They bought 30% more generator than they needed, and that showed up in the fuel bill every month.

Step 2: Confirm the Duty Rating—This Is the One Everyone Misses

This is the step that causes the most expensive phone calls I deal with.

The same 550 kW SDMO diesel generator can be rated three different ways under ISO 8528:

• Standby (ESP): full nameplate power for emergency use, typically up to 500 hours a year, average load below 70%.
• Prime (PRP): unlimited run hours at variable load, average load around 70% of the prime rating.
• Continuous (COP): constant full-load operation, usually derated below prime.

I regularly hear "it's a backup, so standby is fine." For true emergencies, yes. But if the unit will run during peak demand for a month, you need prime or continuous.

In our Q1 2024 quality audit of 140 genset handovers, we found 14 where the duty rating in the contract didn't match the site's actual usage pattern. That's 10%. One of those cost a customer a $22,000 redo when a standby-rated 550 kW unit couldn't carry constant industrial load.

If the spec sheet doesn't say which duty rating it's quoting, it's not a spec sheet. It's a marketing document.

Step 3: Verify Voltage, Phase, and Frequency on Site, Not in an Email

I check the site survey against the spec summary. Voltage, phase, frequency—each one separately. 50 Hz vs 60 Hz. 400V vs 480V. Three-phase vs single-phase. And whether the generator has to provide the neutral-ground bond.

It took me four years to appreciate how often this goes sideways. A customer once ordered a genset configured for 480V/3ph/60Hz. The site was 400V/3ph/50Hz. The modification cost $8,000 and commissioning slipped two weeks. All because nobody asked for the site's electrical configuration in writing.

Step 4: Verify the Components, Not Just the Nameplate

SDMO is a Kohler company, and the Kohler-SDMO engineering partnership is genuine—that's a big part of why I'm comfortable with the brand. But "SDMO generator" is a nameplate. The engine, alternator, and controller are what do the work.

When specifying a genset, check what's actually inside:

• Engine: Volvo, Deutz, Kohler—or a second-sourced engine. Not necessarily a problem, but it changes parts availability and the service schedule.
• Alternator: Leroy-Somer, Stamford, or another manufacturer. This determines voltage response and motor-starting capability.
• Controller: Different controllers mean different remote monitoring and paralleling options.

Buyers often focus on the engine and skip the alternator. That's the first thing a vendor tries to value-engineer out of the spec. I've rejected alternators that couldn't handle the motor-starting requirements of the site. On an $18,000 project, that kind of substitution can turn into a $22,000 redo.

Step 5: Know the Difference Between a Conventional Generator and an Inverter Generator

This sounds like a basic distinction, but it causes real confusion—especially for buyers who start with a small portable unit and then step up to an industrial genset for the first time.

A conventional generator spins a synchronous alternator at a fixed speed (typically 1500 or 1800 rpm) and produces AC power directly. This is what every industrial SDMO genset uses, from 20 kW to 1250 kVA and beyond. It handles surge loads well, and the technology is proven.

An inverter generator runs a smaller alternator at variable speed and converts the output electronically. That gives cleaner power and better fuel economy at partial load, but it's usually limited to smaller sizes.

If you're looking at a Champion 2500 watt inverter generator for a camper, or a Duromax 10000 watt dual fuel generator for home backup, the inverter distinction absolutely matters: inverter units run sensitive electronics cleaner, while conventional units handle the startup surge of an AC motor more easily.

For an 800 kW SDMO generator, though, the inverter question doesn't apply. You're in synchronous alternator territory, and the specs that matter are AVR type, voltage regulation, and parallel capability.

The difference between generator and inverter generator is not a technology hierarchy. It's two different tools for two different jobs.

Step 6: Do the Fuel Math Before You Sign

Fuel consumption is the operating cost that rarely makes it into the business case.

Ask for the fuel consumption curve from the datasheet, not the brochure number. As a rough reference: a 550 kW SDMO diesel generator at 75% load typically burns in the 100-120 liters per hour range; an 800 kW unit lands around 150-170 liters per hour (typical manufacturer data, January 2025; verify against the specific datasheet).

Then multiply by the hours you actually plan to run. This is where the value-over-price argument gets concrete: a "cheaper" genset that burns 5% more fuel costs more in the first year than the purchase price difference—on a 550 kW unit running 500 hours a year, that's roughly 2,750 extra liters of fuel.

Also confirm the day tank size, the external fuel supply connection, and whether dual fuel is an option if you want gas/diesel flexibility.

Step 7: Put the Pre-Shipment Inspection in the Contract

Don't accept "factory tested" in the quotation. Specify it:

• Load bank test certificate at 100% (or at the actual site load)
• Fuel consumption and temperature readings from the test run
• Wiring diagrams, datasheets, and warranty terms
• CE or local compliance certificates

Documentation is the first thing vendors cut to save a few hundred dollars—and the last thing service technicians need when something fails at 2 AM.

The most frustrating part of this job is seeing the same documentation gaps across different vendors and different projects. You'd think a written requirement would prevent it. Interpretation varies wildly.

Common Mistakes That Slip Through

Buying on the lowest quote. From my experience reviewing hundreds of genset proposals over four years, the lowest quote gets something wrong far more often than people expect. That "saved" $5,000 turns into an $8,000 modification and a two-week delay. Every time. Not ideal, but workable if you catch it early.

Skipping the service network check. Verify who handles warranty and maintenance in your region before you buy, not after.

Ignoring fuel quality. Diesel sits in a tank and develops problems. Budget for fuel polishing if the genset isn't running regularly.

Forgetting sound attenuation and exhaust compliance. Site permits can force a $15,000 acoustic enclosure after the fact. Put the dB requirement into the original scope.

Run these checks before you write the purchase order. Fifteen minutes now beats a $22,000 redo later.