The Short Answer: There Isn't One
If you're here because you searched for "100 kw kohler sdmo generator" or "300 kva kohler sdmo generator" and you're trying to figure out which one is 'better'—honestly, I can’t give you a single answer. It depends entirely on what you're powering, for how long, and what your site's electrical configuration looks like.
I’m a project coordinator at a mid-sized electrical equipment distributor. I’ve handled about 200+ generator procurement requests in the last 4 years, including rush orders for a data center that went down during a storm and a last-minute spec change at a construction site where the crane timing was already locked in. So I’ve seen both sides of this decision go right—and go very wrong.
Let's break it down by three common scenarios. Figure out which one matches your situation, and the right choice should be pretty clear.
Scenario A: The 3-Phase Industrial Site (Default Pick for 300 kVA)
What this site looks like
You're powering a manufacturing line, a large HVAC system for a commercial building, or a pumping station. The critical loads are all three-phase motors. Your incoming service is likely 480V (or 400V in some regions).
This is straightforward. The 300 kVA Kohler-SDMO generator (which is roughly 240 kW at a 0.8 power factor) is the obvious choice. The 100 kW unit won't handle the starting current (inrush) of larger three-phase motors. A 50 HP motor starting up can draw 6 to 8 times its running current for a split second. That's enough to trip a 100 kW generator.
A quick reality check from the field
Last year (Q3 2024), I had a client who tried to spec a 100 kW set for a facility with four 30 HP air handling units. They thought the running load was only 90 kW, so it should work, right? Wrong. When the second unit kicked on, the voltage sag was too deep. The PLC-controlled system faulted. They had to swap to a 250 kW unit (close to the 300 kVA) which added a 4-week lead time and $6,000 in re-installation costs. It took me 3 years and about 50 of these sizing mistakes to understand that looking at running load isn’t enough.
Key takeaway for this scenario: If you have more than one three-phase motor over 20 HP, or if you have a transformer-fed load, go with the 300 kVA. The 100 kW is too risky.
Scenario B: The Single-Phase Critical Backup (The 100 kW Sweet Spot)
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You're powering a lighting/fire alarm panel, a server room (with UPS on the front end), and some comfort cooling for a control room. The big loads are single-phase, or the total running load doesn’t exceed 80 kW.
Here, the 100 kW Kohler-SDMO generator is usually the better fit. It's physically smaller, uses less fuel at 75% load, and is easier to place on a concrete pad. Why pay for a 300 kVA if you can't fully load it?
The thing nobody tells you about fuel consumption
A 300 kVA generator running at 30% load (say 90 kW) is horribly inefficient. It's burning almost as much diesel as it would at 60% load because the engine is still running at the same RPM, just with less fuel. The 100 kW unit loaded at 80% (80 kW) will be significantly more efficient. Over a 72-hour run event (like a hurricane outage), that difference in fuel burn can save you $400-$700 in diesel, not to mention fewer refuel trips.
People think bigger is safer. Actually, oversized generators cause wet stacking, which ruins the exhaust system over time. The assumption is 'bigger is safer'; the reality is the right size is safer.
Scenario C: The Mixed Load Site (Where You Calculate, Not Guess)
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You have a mix: some dedicated three-phase equipment (maybe a 20 HP chiller) and a lot of single-phase lighting and receptacles. Total running load is maybe 100 kW. This is the grey area.
You need to do a motor-starting calculation. If the 20 HP chiller is the largest motor, it might draw ~165 Amps for a cycle on startup. If the generator's voltage dip exceeds 30%-35% for that second, the voltage-sensitive electronics (like a VFD or a PLC) will brown out and drop offline. In my experience, a 100 kW generator might dip too far for that single 20 HP motor depending on the generator's alternator specs. I'm not a design engineer, so I can't speak to the exact alternator curves for every Kohler-SDMO model. What I can tell you from a procurement perspective is this: ask your supplier for the 'motor-starting kVA' chart for the specific set. If the chart says the generator can handle 70% voltage dip on a 20 HP motor, you're good with the 100 kW. If not, go up to the 300 kVA.
Honestly, if you're in this grey area, and the price difference between the 100 kW and the 300 kVA is less than 20%, I'd default to the 300 kVA. The cost of the wrong choice (a brownout during an emergency) is way higher than the extra upfront cost (basically).
How to Know Which Scenario You're In
It's pretty easy. Look at your one-line electrical diagram.
- Do you have more than 20 HP total in three-phase motors? You're in Scenario A. Get the 300 kVA.
- Do you have mostly single-phase, low-starting loads? You're in Scenario B. The 100 kW is perfect.
- Are you unsure about the motor starting load? You're in Scenario C. Contact your Kohler-SDMO rep and ask for the motor-starting kVA chart. Don't guess. I say that because I’ve ignored this step before (ugh), and it cost us a $1,200 service call to swap the controller settings.
This isn't a one-size-fits-all answer. It’s what I’ve seen work (and fail) on real job sites. Verify your motor loads and the specific generator specs for your region. Pricing as of January 2025 can vary significantly by dealer and local market conditions.
