I'm the person who reviews industrial generator packages before they ship—roughly 200 packages a year at the distributor where I work. If the spec on the purchase order doesn't match the machine on the skid, I'm the person who has to catch it. In Q1 2024, I rejected about 12% of first deliveries for spec mismatches: wrong voltage configuration, missing automatic transfer switch, control panel that didn't match the contract.
This article is the comparison I run when two very different Kohler-SDMO quotes landed on my desk. One was for an 80 kVA Kohler-SDMO generator at a cold-storage facility. The other was for a 600 kVA Kohler-SDMO generator at a manufacturing campus. Same SDMO generator family. Almost nothing else about the two projects is comparable.
Most buyers compare generators using two numbers: kVA and price. That's a fine first pass, but it misses the reasons machines fail after installation. The way I compare these two is across four dimensions: rating class and real capacity, fuel and maintenance behavior at actual load, installed commercial generator prices, and commissioning risk. At every step, I'm looking for the mismatch between the paper spec and what the equipment will do under real site conditions.
Rating class and real capacity: the first check
An 80 kVA generator at 0.8 power factor gives you 64 kW of usable capacity. A 600 kVA generator at 0.8 power factor gives you 480 kW. Those numbers are at standard reference conditions, meaning sea level and rated ambient temperature. Altitude and heat derate both machines, which is why I check the derating curves before approving anything.
The larger issue is rating class. According to ISO 8528-1 (iso.org), there's an important difference between prime power and standby/emergency power. In plain terms: prime-rated machines are designed for a variable load and unlimited annual run hours. Standby-rated machines are designed for limited running during utility outages. If you buy a standby-rated unit and run it continuously because your process can't stop, it will fail. Not maybe someday—eventually.
We didn't have a formal load-profile review process back then. That cost us when a client ordered a 600 kVA machine based on the sum of all breaker ratings—the classic mistake—rather than on measured demand. The unit ran around 20% load, and the project spec claimed it would support the site's full connected load. The site engineer followed the spec; the spec was wrong from the beginning. The third time we saw that pattern, I created a one-page verification checklist. Should have done it after the first.
Comparison conclusion: The 80 kVA machine is usually easier to size because its application is simpler. The 600 kVA machine demands real load data and a deliberate rating choice. In my experience, almost every large-unit problem we've seen traces back to this one step.
Fuel and maintenance: the counterintuitive part
Our Q1 2024 audit of service records produced a result that surprised our own team: bigger isn't automatically wasteful.
Diesel engines reach their best brake-specific fuel consumption somewhere around 70–80% load. At 75% load, a 600 kVA machine burns more liters per hour than an 80 kVA machine, obviously. But its fuel consumption per useful kWh can be similar, and sometimes the larger machine wins because its engine is operating in a more efficient part of its map. What genuinely hurts is the opposite: putting a 600 kVA machine on a site that draws 90 kW and letting it sit at around 20% load. That is a very expensive way to make a small amount of electricity.
Maintenance scales in the same direction. The 80 kVA Kohler-SDMO generator has smaller oil volumes, a smaller filter set, and simpler cooling. The 600 kVA machine has more cylinders, bigger filters, more oil, heavier parts, and a more involved cooling system. Service intervals are often similar in hours, but each visit costs more, sometimes much more, because the parts are larger and the labor is heavier.
Comparison conclusion: Size the machine to the measured load profile, not to the idea that more headroom is safer. If the essential site load is around 50 kW or below, an 80 kVA unit is a rational fit. If the site needs 350 kW, a 600 kVA unit is not overkill.
Commercial generator prices: where the quote stops being useful
Commercial generator prices aren't something I can quote from a national index, so treat these numbers as directional. Based on quotes logged in our office in Q1–Q2 2024, an 80 kVA Kohler-SDMO generator package with enclosure and automatic transfer switch ran roughly $30,000–$45,000. A 600 kVA Kohler-SDMO generator package was closer to $120,000–$180,000, depending on controller, enclosure, fuel tank, and breaker options. Verify current pricing before you set a budget.
Real talk: the unit price is only the visible part of the cost. What I mean is that the gap between those two price tags is not a quality difference—it's a scope difference: a packaged machine on one hand, and a site-integrated power system on the other, with fuel supply, cabling, protection, acoustic treatment, and installation engineering built around it.
An 80 kVA unit can sit on a modest concrete pad. A 600 kVA machine often needs a much larger fuel arrangement, heavier breaker gear, a crane for delivery, and logistics planned weeks in advance. Don't hold me to an exact multiplier, but I've seen installation costs widen the gap even further than the unit prices suggest.
And if your first thought is that a diesel powered portable generator would be cheaper, I get it. A portable unit can be the right stopgap when someone is on site to start it and the load is small. But when the load needs to come back automatically after an outage—cold storage, manufacturing, communications—you're comparing a temporary tool with a permanent system. That isn't a fair comparison, and commercial generator prices reflect the difference.
Comparison conclusion: The 80 kVA to 600 kVA price jump is not linear, and installed cost grows faster than kVA. Plan around the installed system, not the line item.
How they work, and where commissioning risk hides
If you've already searched 'how does a whole house generator work,' you know the basic idea: an automatic transfer switch monitors utility voltage; when the grid fails, the switch starts the generator; once the engine is stable, the switch moves the load over; and when utility power returns, it transfers back and lets the generator cool down before shutting off. A Kohler-SDMO commercial package works on the same principle, but at a different scale, with an industrial controller, heavier protection, and larger starting loads.
The speed requirement is formalized on the commercial side. According to NFPA 110 (nfpa.org), emergency power systems are classified by time to restore, and a Class 10 system must accept load within 10 seconds. That's where the familiar 10-second expectation comes from.
Commissioning risk is where these two sizes really diverge. At 80 kVA, we can usually get a mobile load bank onto the site to verify the machine under real load. At 600 kVA, a full load-bank test requires specialized equipment, and in our region there aren't many suppliers with that capacity. That makes it tempting to skip the test.
Two years ago, we had exactly that temptation. A 600 kVA package had to be commissioned before a facility shutdown, and we had two weeks. Normally I'd insist on a full load-bank test before sign-off. But no 500 kW load bank was available in that window, and the operations manager was waiting. We signed off using the factory test certificate, a visual inspection, and a no-load start test.
In hindsight, I should have pushed back on the timeline. The machine ran fine, but the residual risk sat with us, not with the customer. That's a feeling I don't want you to replicate.
Comparison conclusion: The larger the generator, the more the verification process becomes the risk. If you can't test under load before acceptance, you're accepting paperwork instead of proof. For a 600 kVA installation, schedule the load-bank test when you order the machine—not when it arrives.
Which one should you pick?
I won't tell you that one machine is simply better than the other. The right choice depends on the site.
- Choose an 80 kVA Kohler-SDMO generator if your essential load sits around 50 kW or below, you need automatic backup rather than a manual portable start, and you want a smaller installation footprint.
- Choose a 600 kVA Kohler-SDMO generator if your essential site load is in the 300–450 kW range, your operation genuinely cannot stop, and you're ready to treat fuel supply, cooling, and commissioning as a project from day one.
Both machines fit the SDMO generator line well. What separates a successful installation from an expensive correction isn't the badge on the alternator. It's whether someone verified the load profile, rating class, derating tables, and commissioning plan before signing the purchase order.
Five minutes of verification on the front end beats five days of correction on the back end. In my job, that's not a slogan. It's how I avoid the next rework.
