SDMO Generator FAQ: Sizing, Solar Alternatives, and Whole House Backup Costs

I've been a procurement manager at a 200-person building products company for over six years. That means I sign off on equipment purchases, track every invoice, and deal with the consequences when a 'deal' turns out to be anything but. A lot of my spreadsheet space goes to backup power: SDMO diesel generators, solar options, and the occasional propane RV generator someone thinks will run the whole plant. This FAQ is built around the questions I actually hear in the buying process. I'm not an engineer, and I won't pretend to be one. What I can give you is a procurement perspective on size, cost, and total cost of ownership (TCO).

What is an SDMO generator, and why do I keep seeing 'Kohler-SDMO'?

SDMO has been part of the Kohler group since 2005, so 'Kohler-SDMO' is more than a badge. It's a generator that combines SDMO's industrial diesel experience with Kohler's distribution and support network. In procurement, that relationship matters. I've seen buyers pick a slightly cheaper unit from a brand nobody can service, then wait months for parts. The reverse is usually true with Kohler-SDMO: the price might be a bit higher, but the support network is already in place. People think expensive generators are overpriced. The opposite is closer to reality: support infrastructure costs money, and it's part of what you're paying for. When I compare quotes, I ask whether the price includes a dealer startup and commissioning visit. That's where hidden costs show up. A machine that isn't commissioned correctly can fail weeks later, and that's not covered by warranty.

Should I buy a 30 kW SDMO diesel generator or a bigger unit?

If you're asking this question, you're already in the right territory. A 30 kW SDMO diesel generator is a good fit for a small manufacturing line, a farm, a telecom site, or a building that needs to keep critical loads running. It'll handle lights, pumps, HVAC controls, and maybe a small compressor if you stagger the starts. The problem is starting current: motors can draw two or three times their running load for a few seconds. A 30 kW set can trip if someone cycles a big motor while it's already loaded.

So don't just buy the biggest unit you can fit. Oversizing creates its own issues, including low-load 'wet stacking' in diesel engines. A generator that's too big for the load can build up unburned fuel in the exhaust, which shortens engine life. A generator that's too small just trips when you need it. Neither one is a bargain. What I do now is get a load study before sizing. It costs a few hundred dollars and can save you from buying the wrong machine. As of early 2025, the quotes I've seen for 30-50 kW SDMO generators vary significantly based on options and dealer, so verify current pricing before you budget.

When would someone actually need an 800 kW Kohler-SDMO generator?

An 800 kW Kohler-SDMO generator is not a residential machine. That size shows up in data centers, hospitals, water treatment plants, manufacturing lines with large motors, and commercial buildings that need to keep hundreds of tons of cooling running. These aren't simple purchases. They often come with paralleling switchgear, fuel day tanks, concrete pads, and acoustic enclosures. The generator is maybe half the story.

If you're shopping for an 800 kW unit, you probably know your load profile. If you don't, that's a red flag. I'm not an electrical engineer, but from a purchasing perspective I would never approve a project of that size without a third-party load study and a full installation quote. If the load truly requires 800 kW, redundancy matters too. I'd rather have two units sharing load than one giant unit with a single point of failure. But again, that's a design decision, not a budget call. I've seen installation costs surprise people more than the equipment cost. That's the total cost number that matters.

Can a 10,000-watt solar generator replace a diesel generator?

The short answer is no, not for continuous backup. A 10,000-watt solar generator sounds like a lot, but it's really a battery bank with an inverter and solar panels. It can keep a house going for a while, but when the battery is empty, you're waiting on the sun or the grid. A diesel generator just needs fuel. I'm not a solar engineer, but from a TCO view, battery replacement can wipe out any fuel savings.

For short outages, a 10 kW solar generator can be a decent option, especially where diesel delivery is difficult. But read the small print. Per FTC advertising guidelines (ftc.gov), claims have to be truthful and substantiated, but marketing numbers still need a careful look. '10,000 watts' might be peak surge, not continuous. I've also seen solar generators with big wattage stickers but limited 120V output. And some inverters struggle with motor starts and non-linear loads. That's a surprise nobody wants during an outage.

Is a propane RV generator any good for whole house backup?

A propane RV generator is designed for a motorhome, not a suburban house. Most are in the 3.5 to 5.5 kW range. That's enough for a fridge, a few lights, a sump pump, and maybe a furnace blower. It won't run central AC, an electric range, and a well pump at the same time. If you already own one, it's better than nothing. But if you're buying one specifically for whole house backup, I'd probably look at a fixed standby unit or a properly sized portable generator instead.

I'm not an RV equipment specialist, so I can't give you exact runtime charts. What I can tell you from a cost perspective is that propane storage and cold weather performance need attention. If you already have a large propane tank for heating, the math changes. But a pair of little RV tanks won't carry a house through a multi-day outage. You don't want to find out about low propane pressure in the middle of a storm. The cheapest generator in the world is useless if its fuel system can't deliver when needed.

Is a whole house generator worth it?

I get this question more than any other, and the honest answer is: it depends on what an outage costs you. Not what it feels like, but what it actually costs. If you've ever lost a freezer full of food, a day of remote work, and a sump pump failure, you already know the number. For some people, one outage pays for the generator. For others, the annual maintenance cost is more than the outages would ever cost.

Maybe I'm biased because I track expenses, but I'd run the math before calling anyone. A typical whole house standby system in my experience lands somewhere between $8,000 and $20,000 installed, and that goes up fast with transfer switches, propane tanks, and concrete pads. That range is wide because site conditions vary. If you have medical equipment or work from home, the convenience part has a real dollar value. Add that to the calculation. Get three itemized quotes and compare the installation scope, not just the headline price. And ask about the service plan. That's where long-term cost hides.

What's the hidden cost nobody budgets for after buying a generator?

Testing and maintenance. It sounds boring, but it's the reason a cheap generator becomes expensive. I only started budgeting for annual load bank testing after we skipped it once and then found out the 'new' generator wouldn't accept load when we actually needed it. The repair invoice was more than five years of a basic maintenance contract would have been.

There's also fuel management. Diesel goes bad, water gets into tanks, and batteries die. A generator is a machine, not a magic box. Load bank testing sounds optional, but it's how you know the generator can actually carry what it's rated for. If a dealer offers a preventive maintenance plan, include it in the total cost. Over ten years, the difference between a solid unit and a lightly built one can be bigger than the purchase price. That's the number I care about.