# Any benefit to liquid vs air cooled standby 22KW



## MikeBW (Nov 8, 2019)

I'm in pre-purchase phase on a residential standby unit. I'm at 22KW requirement and see that generac offers both air cooled and liquid cooled units at this capacity.

Of course, liquid cooled is $5K additional. Is there any reliability or run-time benefit to liquid cooled vs air cooled? My target in the southeast is 7 day run time. Both can do that but air cooled is cheaper, better fuel use, quieter. Is there a reason to spend more?


----------



## tabora (Sep 6, 2018)

MikeBW said:


> I'm in pre-purchase phase on a residential standby unit. I'm at 22KW requirement and see that generac offers both air cooled and liquid cooled units at this capacity.
> 
> Of course, liquid cooled is $5K additional. Is there any reliability or run-time benefit to liquid cooled vs air cooled? My target in the southeast is 7 day run time. Both can do that but air cooled is cheaper, better fuel use, quieter. Is there a reason to spend more?


 I guess the question is where exactly are you located and what temperatures do you anticipate enduring while running for 7 days? Liquid cooling is likely to deal with higher temps better than air cooling does. At 22KW, you're at the very top end of air cooled generators, and the bottom end of liquid cooled.
https://www.americasgenerators.com/...Air-Cooled-and-Liquid-Cooled-Generators-.aspx


----------



## MikeBW (Nov 8, 2019)

Thanks. I understand 22KW is the typical cutoff between air and liquid cooling. I'm in Miami looking for multiday post-storm backup. Since Generac makes a 22KW in air cooled and water cooled unit, I was wondering if the benefits of a water cooled unit are worth the almost two-fold price. I also understand annual maintenance costs will be greater.

I would be willing to pay a premium for robustness and dependability and longer run times. However I cannot find hard facts that water cooled units provide such benefits and was hoping some pros would have some real life observations on this.


----------



## KRE (Nov 29, 2011)

Never base your final generator choice on price, or an ad. Talk to those who have what your looking at, to see if their money was well spent or otherwise. Once you get above 12 KW I would suggest never buying anything above 1800rpm or any gen set with a built in transfer switch. Buy once an cry once, as paying for a quality back up power is way cheaper up front vs the back side. Plus not having it available when it's needed most is sicking, plus can be dangerous depending needs.


----------



## exmar (Jun 29, 2015)

Curious why you need 22KW when most of us get by on a lot less?? Is that a realistic assessment of what you actually need in an outage or a "worst case, belt and suspenders" approach? Certainly a liquid cooled unit is going to be a better quality than a air cooled unit, question is do you need that kind of quality and reliability? "South East" probably means you have to deal with Hurricane related outages, evaluate how often and duration you've experienced into your equation. Balance the preceding questions against your finances. 

Good luck, 
.


----------



## KRE (Nov 29, 2011)

20-25kw is a normal size for a average home package. Once you add up all that could be on at one time, or if you heat with electric it can add up quick. There are homes in this country that have much larger units installed, depending live style based on needs or wants. The largest I've ever installed an commissioned was a 350KW Onan in a home in Miami Fla. It took all of it to run that home, pool heaters, atrium A/C units, elevators, kitchen, ect. My home unit is a 25KW I built from scratch, an many times while working in the shop it will peak at 23.5KW with the home running, plus a lathe, welder, planer, running at the same time. Many homes are used for work places, as well as entertainment. The last thing you need is for the power to go off an stop a project from being completed on time, or kill a business party. Then add the fact if the power goes off an you are away, you could lose everything in your freezers, or have the basement full of water, or busted plumbing do to freezing upon return. Many people see whole home backup power as a safety net, that does not require baby setting.


----------



## speedy2019 (Jan 29, 2019)

If you used that amount of power all at once, your bills would cost a fortune.. You might use a fraction of that at once Im guessing


----------



## KRE (Nov 29, 2011)

speedy2019 said:


> If you used that amount of power all at once, your bills would cost a fortune.. You might use a fraction of that at once Im guessing


 Well lets look at that. Let's just say it's a total electric home in the Midwest. The heat pump is having issues keeping up with the cold so now the emergency heat strips come on. That by it's self could be 7-15KW alone then add the fan at 0.8-1.2 kw running an now we are at 7.8 on the bottom side an 16.2 on the top side. The Freg is now wanting to run as well as the freezer kicks on that adds another 1.8-2.7 depending size an model. So now it's 9.6 to 18.8KW then the Water heater comes on another 3.2 to 4.5 KW here we are now at 12.8 to 23.3 an the TV, radio, or any battery charging has not been added yet. Can one live with a rope start sure, but your going to be w/o many things an/or playing, what do/can I power now? If you do not heat via electric a 15kw genset is the norm for up to 2K sq ft, assuming no large shop tools are involved. Also remember reactive inrush is a hard number the genset has to deal with, if you can fully control when inrush happens yes a smaller set will suffice. This can be done with device preference lock outs, interlocks, or load shedding devices properly installed. Once you get past XXX dollars for backup power it does not cost that much more to do the whole home properly. The draw back is if you have a quality whole house set an the power is out for 3 days plus, you will not believe the number of people who want to be your best friend/s. BTDT Most power Co's (utility's) size the average home at 5-6.5 KW as not everything is not on at once an many homes have no one home 24/7.


----------



## exmar (Jun 29, 2015)

My neighbor has a three bedroom house, electric heat, water heater, dryer, etc. the 13KW has worked just fine for about ten years. He does have a gas range which helps some. I have a similar house with gas heat and got along fine with a 3500W, upgraded to a 5500W. Don't use the electric dryer during outages which usually are a couple of hours up to 1-2 days.

Comes down to how often outages occur, willingness to deal with small inconveniences and how much you want to spend.


----------



## KRE (Nov 29, 2011)

Back up genset size depends upon needs & wants. Many believe just having the very basics is not worth the cost of a larger investment an that's fine. Then you have people who are out restoring power for every one else that will not allow their family's lives to be interrupted. The other need is for people who can not/able to haul a genset out an hook it up by their self's. Many have health issues or have family members that are bed/wheel chair ridden, who can not survive w/o electrical power. Home owners that work from home normally require more power an don't have time to drag something out during a high end conference call ect. There are many places in this country were power is not 100% 99.95% of the time. The reason many are now targeting the 15-25KW market but any unit that size or manufacturer that is sold in a box store has way higher life cycle costs compared to those sold thru other outlets. That old, We sell it but don't service it, is a clue from the gate.


----------



## jkingrph (Sep 18, 2017)

I am using a 11KW Honda for my almost whole house, all electric with heat pump. When we need the geneator i manually turn off circuit breakers to hot water tank, and the emergency heat strips in the furnace. I do have a set of gas logs in a fireplace and a couple of 40 lb tanks of propane.

Not exactly a generator, but a big Scag lawn mower. I had the option of a liquid cooled engine for an extra $100 when I purchased it 13 years ago. It's still going strong . I think the liquid cooled especially in hot weather will give a cooler longer lasting engine


----------



## MikeBW (Nov 8, 2019)

Thanks everyone.

I see some comments here that liquid cooled / 1800 rpm would in fact be more reliable than air cooled / 3600 rpm at thr same KW rating. Considering the total package (propane tank, install, etc) this would add about 20% to the overall cost. I may just do it.

With regard to required capacity since I'm targeting a 7 day runtime running perhaps 24 hours a day, I'm targeting running at 50% load for optimal mileage.

Yes I could squeak through with a 16KW air cooled 3600 rpm and a lot of load shedding, but I'm not comfortable expecting it to run reliably for 7 days at 70% load or higher.


----------



## Gizmo (May 21, 2013)

It is my belief that 7 days is an extended run period but not an unrealistic demand considering your location. A water cooled unit would be a good investment for your home.


----------



## Kfainone (Sep 4, 2019)

I agree with everything that everyone has responded with as I was in your position a little under a year ago. Power was out after snow storm and following cold snap. I used a portable generator (9000 watts) to run several small heaters placed downstairs. I placed blankets in the doorways to keep the heat from going upstairs which we had vacated already. The wife is super sensitive to certain odors and complained when I would come back in after refueling the generator. This got me started on a more permanent solution. I contacted an old electrician friend who I trusted and used several times in my industrial projects and we got started with the electrical part of the install. We had agreed that diesel was the direction I would go for this install. I had read that many people who had propane or other gaseous system discovered that 24 hour a day run times were harmful to the equipment. Couple this with people who thought they could live off grid just to find that their gen sets would give up after 3 days to two weeks. So, I don’t feel a diesel generator is perfect for me or others but it did offer me piece of mind on many issues I worried about. As for myself, I was planning around a 20kw unit to handle most of the house. We had already selected and installed a 200 amp Asco series 300 transfer switch. I felt we could be happy in the event of a power outage and just stay in the main level of our home. Then, the electrician said we woul need to discuss load shedding since my wife wanted a totally automated system in the event I was not home. This added another $3000 which I felt was better to put towards the generator. Remember this is my first time at this and figured I would make some mistakes along the way. When it came time to actually buy the machine itself, I knew I wanted quality parts but I also wanted simple. I wanted analog controls, and I really didn’t want want a turbocharged engine. I priced a brand new machine which came in just under $17000. So I sat down with my electrician and we decided to look into a used but refurbished unit. He directed me to a company in Georgia that specializes in this area. I ended up with 37kw machine that started its life as a Koehler unit at municipal building. The engine had 800 hours on it when they took possession of it. They replaced the old Koehler power unit and replaced it with a brand new Stamford UK built unit. The radiator was replaced and it received brand new McPherson controls. The engine is a normally aspirated 4 cylinder John Deere 4239. They painted everything and installed a battery charger and block heater. So for $10500 for the generator, I got a machine that does the entire house, runs like a champ, doesn’t have the extras that just seem to complicate things. Yes, it is an older engine from what I understand, it is a 3.9 liter where everything I seen was in the 2.2 - 2.5 liter size range. It is a little bit noisier but I have ways of dealing with that. And yes, now the neighbor wants one.


----------



## HarryN (Jun 2, 2018)

MikeBW said:


> I'm in pre-purchase phase on a residential standby unit. I'm at 22KW requirement and see that generac offers both air cooled and liquid cooled units at this capacity.
> 
> Of course, liquid cooled is $5K additional. Is there any reliability or run-time benefit to liquid cooled vs air cooled? My target in the southeast is 7 day run time. Both can do that but air cooled is cheaper, better fuel use, quieter. Is there a reason to spend more?


I am surprised that a liquid cooled unit would be louder than an air cooled unit. Isn't noise reduction supposed to be one of the benefits of liquid cooling?


----------

