There's no single 'best' generator for everyone. Anyone who tells you otherwise is selling you what's on their truck. In my role coordinating emergency power for critical infrastructure projects—everything from hospital backups to data center installations—I've seen the same mistake made over and over: buying a generator that's either way too big (and burning fuel you don't need to) or too small (and failing when it matters most).
The same goes for transfer switches. People think a manual switch is 'just a lever.' It's not.
Here's what I've learned from dozens of installations across three distinct power scenarios. Which one fits your situation?
Scenario 1: The 80 kW Diesel Generator – For the Essentials
This is your bread-and-butter unit. An 80 kW diesel generator is typically enough to power a small commercial building, a large home, or a small workshop. Think: lights, HVAC (if it's not massive), a few computers, and some critical machinery.
Who this is for:
- A small medical clinic that needs to keep the lights on and refrigeration for vaccines.
- A farm with a few essential pumps and a milking parlor.
- A home with a sump pump, well pump, and basic appliances.
What most people don't realize: That 80 kW rating is often for standby power (running on natural gas or diesel for a limited time). If you need it for prime power (running 24/7), derate it to about 60 kW. I've seen contractors spec a generator based on the nameplate, only to have it fail after 48 hours of continuous use. It's a rookie mistake.
Scenario 2: The 550 kW SDMO Diesel Generator – The Industrial Workhorse
This is where things get serious. A 550 kW SDMO diesel generator is a beast. It's used for medium-sized manufacturing plants, large retail stores, or as a backup for a small hospital wing. It'll run multiple production lines, a chiller system, and a hundred people's worth of lighting and computers.
Key consideration: A unit this size isn't something you plug into a wall. It requires a dedicated concrete pad, a substantial fuel supply (think: a day tank or a buried diesel tank), and a serious transfer switch.
Insider knowledge: SDMO generators in this range are known for their reliability, but I've noticed the aftermarket controller support varies by region. If you're in a remote area, make sure the dealer has a stock of replacement controllers. A good generator is useless if you can't start it because a circuit board failed and the part is on backorder for six weeks.
Scenario 3: The 1000 kW Kohler SDMO Generator – The Heavy Lifter
Now we're talking about a facility-wide solution. A 1000 kw kohler sdmo generator (note: Kohler and SDMO are separate brands, but often paired in large projects because of their compatible control systems) is for a full hospital, a data center, or a large industrial complex.
The reality: At this scale, the generator itself is only part of the cost. The installation—the trenching for fuel lines, the massive concrete pad, the automatic transfer switch (ATS) system, and the paralleling gear if you have multiple units—can easily cost as much as the generator. People focus on the '1000 kW' number. The real focus should be on the total cost of ownership.
In March 2024, I worked on a project where the client saved $12,000 by selecting a slightly used 1000 kW Kohler unit over a new one. The unit had 200 hours on it and came with a full factory warranty transfer. The 'new vs used' debate isn't black and white at this scale. Sometimes, the used unit with a known service history is a better bet than a new unit from a distributor you've never worked with.
The Critical Link: The ASCO Manual Transfer Switch
This is the part people get wrong. You can have the best sdmo-generator in the world, but if your transfer switch isn't right, you're dead in the water.
An asco manual transfer switch is the safest way to connect a generator to your building's electrical panel. It physically isolates your generator from the utility grid, preventing backfeeding—which kills linemen and can start fires.
Why manual vs automatic?
- Manual: You have to walk to the switch and throw the lever. It's cheaper, more robust, and less prone to failure. It's what I recommend for 80 kW and even some 550 kW installations, especially if the generator is only used a few times a year.
- Automatic (ATS): The system senses a power loss and starts the generator automatically. It's more convenient, but also more expensive and introduces another point of failure. This is necessary for 1000 kW installations in critical facilities where every second of downtime costs thousands of dollars.
How to install a transfer switch for a generator: This is not a DIY project, but you should understand the principle. The transfer switch sits between the utility meter and your main breaker panel. There are two incoming power sources: utility and generator. The switch selects which one feeds the panel.
- Size the switch correctly. A 200-amp switch for an 80 kW generator is typical. For a 550 kW generator, you might need a 1200-amp or larger switch. Don't undersize it.
- Proper wiring gauge. The wires between the generator and the switch need to handle the full load. Undersized wiring creates voltage drop and a fire hazard.
- Interlock kit (if no dedicated switch). Some people install a generator interlock on the main panel instead of a separate transfer switch. This is code-compliant in many areas, but it's less convenient and doesn't provide the same level of isolation. I prefer a dedicated ASCO manual transfer switch for safety.
Looking back, I should have pushed for an ASCO manual switch on a 550 kW project early in my career. The client opted for a cheaper automatic transfer switch from an unknown brand. It failed during the first real power outage. The automatic start didn't engage. The switch was stuck in a 'neither' position, providing no power from either source. Cost them a weekend of downtime and $9,000 in emergency electrician fees.
How to Decide Which Scenario Is Yours
Here's a simple framework I use when triaging a new inquiry:
- Step 1: List your critical loads. Everything that must stay on during an outage. Add up their running watts.
- Step 2: Add a 20% buffer. You never want a generator running at 100% load. 80% is the sweet spot for efficiency and longevity.
- Step 3: Decide on manual vs automatic. If you're okay with a 1-2 minute walk to the switch during an outage, manual saves money and increases reliability. If you can't afford a 30-second gap in power, go automatic.
- Step 4: Know your fuel. Diesel is more energy-dense and storable than natural gas, but requires more maintenance (fuel polishing, injector issues). Natural gas is cleaner but requires a constant supply from the grid—which might go down in a major disaster.
Your specific needs—the size of your facility, the criticality of your operations, and your budget—will dictate the right combination. There is no universal answer.
