I recall it's been discussed, but thread is archived and looking for new data/info.

Trying to get  a whole-house standby generator installed. house is +/- 4600sf, with full basement and the usuals (two refrigerators, dual A/Cs and gas furnaces, water treatment, well pump*, router, dishwasher, microwave, W/D, etc). * only oddity is that the well pump is on a 50amp circuit; apparently unusual. Either would be natural gas fueled, if it makes a difference.

Generac guy recommends 24KW, 3600rpm, air-cooled unit. the largest air-cooled. Installed price just under $10K.

Kohler guy thinks we can get by with their 20KW unit, their largest air-cooled (since the next step is the astronomically expensive 1800rpm, liquid cooled unit. He recommended if we go that route skip the 22KW unit and go to the 30KW). He suggested that Kohler is a better unit because maintenance and servicing is easier/less expensive, since it has hydraulic lifters, better switching. Haven't received the quote yet, but he thought it would be around $11K installed.

All I've read suggests both are sound. There does seem to be a slight edge to the Kohler as better engineered and built, but it is not overwhelmingly convincing. Is that true? If so, would 20KW be adequate for a house this size?

Since lead times are already long and growing longer would appreciate immediate input from those who know. I want to pull the trigger this week. Thanks.

I would drop the coin for 1800 RPM Kohler or Cummins. My past experience with Generac is less than stellar.

We have a 22kw propane Generac.  House is 4300sf with 2 HVAC (propane heat)units, 450' deep well pump 240kv (30amp breakers)., 2 refer's, etc.  One HVAC and elect oven are not hooked up to HVAC as we didn't want to find out at the wrong time we had to much load for the gen.  Installed around 4 years ago for $11k.  Half the cost was new panel and wiring.  Got local permits just in case for insurance purposes.  Some contractor said permits aren't required yeah right.

Edit: if you want to run the unit 24/7 get a 1800 rpm.

Thanks. Hope to hear from some more guys, but you've both been helpful - if depressing. The 1800rpm units are twice the cost of the air-cooled (so we would be looking at $20K or so ... ouch).

I’m guessing fuel cost isn’t a concern for you.

Given the cost difference, I’d go with the Kohler.

General 22kw standby system here. House is all electric w/ 5 ton heat pump w/propane furnace backup. Load management module for the heat pump installed but it has never needed to trip that I know of (other than delaying start after initial switchover). We have had the system for about three years now and have no complaints. The longest single outage since install has been about 23 hours.

Regarding oil changes during long term operation, the manual specifies shutdown every 24 hours to check oil & allow cool down before restarting. Oil changes are at 100 hour intervals.

Fuel cost not an issue. Why choose Kohler?

Thanks. The bold part seems a bit of a pain. A week-long outage would require an oil change. Not a huge deal but shorter than I would have expected. Guess that's the rationale for the 1800rpm units ...

Your experience suggests that the 24kW unit would be more than adequate. Maybe could get away with a smaller one.

I may have mis-remembered the oil change interval, I took a quick look and I think the current docs say every 200 hours for guardian models from 2013 on.. It's a pressurized oil system with filter.

Our 22kw was spec'd for the 5 ton HP.  A soft start on the HP (like the one we just installed) might have made a much smaller unit (14kw?) viable.

Sounds very much comparable to our situation; sounds as though we would have reserve if we went with the Generac 24kW. No probs in 4 years? It's still under warranty too. Thanks.

I would prefer the 1800rpm/liquid cooled unit (for long-term reliability, longer outages, and quiet), but at $20k+ it is hard to justify. If we were going to stay here forever I'd do it, but we are sure to move again in, probably, fewer than ten years.

While I don’t think Generac makes a bad unit, in my opinion the Kohler is better. Not $5k better but probably $1k better for a unit of that size.

Disregard. Bad math. Whoops.

I have a 425 ft well and the pump is a 240v on a 30 amp breaker. It starts and runs quite easily on my 5800 watt generator with plenty of power to spare.

My math was wrong. I doubled my wattage somehow.

We have the newer 1800 rpm version of the 30KW Kohler and I'm very happy with it. Natural gas, QUIET!!!!!, has wifi notification for status changes and more. It' sour second Kohler and the first one lasted 12 years with moderate to heavy usage. Our power drops a LOT year round. The older units used a "brush" system and the housings that kept the brushes in place failed. The new unit has an entirely different setup. I'd buy another one.

When I bought our 22kw Generac it was the largest air-cooled made. Anything above that was water cooled and double the price. I have had Onan generators in motorhomes, a 7 KW diesel in a 5.5 KW gasoline and they're very reliable but I don't know if onan makes whole-house generators, I know they make big ones for boats.
At any rate, the 22kw Generac does our house with two AC units electric heat, electric hot water tell her to refrigerators in a separate freezer. It just has to shed one AC at a time.

Thanks to all of you who replied; all of your input was very helpful in our assessment. We went 'round and 'round with this, but decided to go with the Generac 24kW air-cooled gen.

Would love to have gone with either Kohler or Generac liquid-cooled, low-rpm gens, but at more than double the cost, simply couldn't justify it.

The determining factors it the decision were:

* the Generac unit's additional 4kW, though not a huge amount, provides a comforting 'cushion' with double A/Cs and a deep well.
* the Generac installer had a cleaner, simpler installation plan. Fewer holes in the house, fewer moved connections, better siting, etc.
* the price difference.
* the Generac contractor has handled both units; they are satisfied that the current general units are at least on par with Kohler's, so
* were able to offer a great warranty.

We should have it in-place in about a month to six weeks (ahead of Kohler's estimated schedule, too).

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