Need advice on backup/standby generator Onan or Kohler

I am considering a backup generator for my home here in West TN. We have somewhat frequent ice storms, tornadoes, and we are waiting for the New Madrid fault to break loose with the 9.0 earthquake.

All of the units I am looking at are propane or natural gas.

I have two AC units, one is a 5 ton that draws 21 amps 220V, another a 3 ton that draws 13 amps 220V. I have two electric water heaters that draw 17 amps 220V each. We heat with natural gas. Our stove and dryer are natural gas too.

Onan and others make an air cooled, 3600 RPM 20KW,unit that has the ability to shuffle two loads to prevent the unit from overloading. I think others make similar units. I worry about using one of those because it has basically a lawn mower engine driving it.

Nearly every knowledgeable person I have asked about generators has told me to stick with 1800 RPM liquid cooled units, and lean toward the Onan or Kohler units and avoid Generac and other Home Depot type units.

I went and looked at the Onan-Cummins 30 KW, liquid cooled, 1800 RPM unit. It looked to be sturdily built and heavy duty. I have not yet
inspected the Kohler 25 KW, liquid cooled 1800 RPM unit. I am sure that it is a good unit. Both of these units utilize a GM 3.0 liter industrial engine. It is a modern Vortec type with hardened valve seats.

Although money is some consideration, I would rather spend more money and get what I need that will last me the rest of my life rather than skimping and getting a lesser unit. That being said, If I need to run the unit for any length of time the fuel efficiency will be a consideration. None of the units seem to get good economy at a 25-50% load. So that means I don't want to oversize the unit.

I am positive that a 30KW unit will easily run everything in my house at once, I am also sure that the 15 KW unit would be too small.

I think I will be using the automatic transfer switch because it costs no more than a manual switch and it will take away the worries of being away from home for a day or two.

I am told that Kohler makes a dual fuel nat. gas and propane unit. I like that because the nat gas is cheaper, but if we have the big earthquake we could be out of nat. gas for weeks or months. And electricity, for that matter.

I read on the forum where people are getting by with much smaller units, but they seem to be up north where AC is an option, not nearly a necessity like it is here.

Any words of wisdom would be welcome.

I put in a 30K kohler last fall.It has the air cooled engine.The engine is an overhead valve
industrial type engine.I'm in west central ohio and used it 3 times last winter and 2 times this
summer so far.The other day it had 20 hours on the hour meter.We have it set to start up every saturday at 3:00 to test.It came with a transfer switch and is wired to a 200 amp house box.

I like the idea of LP or Natural gas so as to avoid stale or watery fuel issues,,,,,,If possible Id recommend one with an automatic exercise controller so it works and cycles now and then,,,,,,,,,If you want to use only a 2 Pole Transfer Switch (i.e. not a switched Neutral) the genny must NOT have its Neutral bonded to its iron frame as is typical for a "Seperately Derived System" (may well be how the genny is factory configured???) instead you carry the gennys Neutral to the utility Neutral and you carry an equipment GroundING conductor out to the gennys iron frame.

You sure 15KW is too small if theres any way to switch/distribute/shed loads to some extent???

I agree with 1800 RPM and liquid cooled FWIW. Onan now Cummins Onan arent pushovers ya know when it comes to gensets.

Keep us posted on the project, sounds pricey but a quality undertaking

John T Too long retired EE

I would go with an air cooled unit to reduce the maintenance. The liquid cooled would have a water pump, radiator, etc. You have to consider the total hours that these will run. I would bet you would not put 300 hours on it in 15-20 years.

30K with automatic transfer switch.

There does not seem to be any advantage in fuel economy by dropping down to the 15 KW liquid cooled Kohler vs the 30 KW liquid cooled Onan. The Onan uses .14 gal/hour at 100% and .25 gal/hour at 25% (7.5 KW). The Kohler uses .19 gal per hour to produce 7.5 KW.

7.5 KW is 34 amps @ 220 volts. That would seem to be my most likely load. Let an AC, oven, or water heater kick in and it could exceed the 15 KW's capacity.

.19 to .25 doesn't seem to be significant compared to giving up the 30 KW capacity and never having to worry about an overload.

I would go with the units that run at the lower rpm,they arent beating themselves to death like the higher rpm units. Bill

You sound like you are afraid of the big one and where do you think you will get any type of fuel or havent you thought about that All you realy need is one that will pump water and that means 240 probably and to lite a few lites and keep the furnace going to keep warm. Are you and can you make the mounthly checks as to starting and so forth in an emergency situation roads blocked so forth having enough fresh fuel.

I have a Generac 3600 rpm unit, cost $3200 + $300 for installation. It runs my whole house, most recently during a 30 hr outage last week. It has a automatic transfer switch. I don't run some stuff when the power is out. Like the stove. It is a propane unit. I priced these units several years ago, a 30K unit, installed was 15K then. The 15K unit does what I need.

Well, the question becomes how much you're willing to lower your standard of living. A few years ago we survived with a 4k gasoline unit for almost a week. That meant rotating loads, cutting off about everything not absolutely necessary to survival. Water, heat, and refrigeration come to mind. We have animals, and water is an absolute necessity, but it doesn't have to run continuously. Same with heat and refrigeration, can run a couple loads at a time, turn off others. Do you really have to run full house AC, or could you get by without it in a pinch? Takes a bit of work, but can get by with far smaller (read cheaper) unit. Now have a 4k and a 5K unit that I picked up fairly cheap. Yes, they're B&S lawn mower grade units, but I don't expect to wear them out in my lifetime. Propane or natural gas would be nice, and probably cheaper to run, but again, initial costs are far higher. Water cooled unit would be nice, but again far more expensive. Guess it boils down to how much you are willing to spend, how much you can cut back on electrical demand, how many hours per year you are actually going to need auxillary power. By the way, no matter what you do, home grown electricity is going to be far more expensive than commercial power. Look at a home generator as a stop-gap measure until commercial power is restored. And yes, having a generator has saved my bacon several times - literally.

I have a 30K Onan unit. I have had it about five years. It was about $10000 installed with an automatic transfer system. It also cycles once each week and runs for a short while to keep the batteries up/going.

My unit is propane powered. I have a 1000 gal tank for the house anyway. I have ran it for a week with full house services. My furnace is a corn hot water one and we cook with propane. Hot water heater is electric, if corn stove is going it does not draw any power. During that week I think it used about 150 gallons of propane.

I have been very happy with the whole system. I had a tractor powered PTO generator before. I spent a long cold day getting a tractor started when the electric went out when it was thirty below. I had this put in before the next winter. I am at the end of a long line. I am the last to get fixed if anything happens. My generator runs for real 5-6 times each year. I think it has about 300 hours on it.

I didnt see this post yesterday.

I would get a minimum of a 15 kilowatt unit which will be about a 100 amp unit.
I would go with the Kohler unit. Higher quality then Generac.
I have a portable 10HP unit that I have to hook up each time. But I only lose power on average about 10 hours per year. I dont need a whole house standby gen set. At least I hope I never do.
My wifes best friend had a 17KW Generac installed for $6000 I am told. Nice, but I think Kohler makes a higher quaility unit then most others.
If I was you look on Craigslist or ebay for a good condition used one cause somebody might want to sell theirs and need the money.
I have a hard time spending $4000 or more on something that I may never really need.
The longest I have ever been without power was 15 hours I think.

I have a 17K Generac unit with transfer box hard wired in. $3000.00 ten years ago. I paid myself to install it. Never misses a beat. Absolutely love it.

I went on the Kohler website and a 15 Kw is 65 amps and the 18 Kw is 75 amps.
www.Kohler.com
I would like to get one of these.
Lots o money though.