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Kohler 20kW Composite Home Standby Generator

Kohler Electric Generators and Accessories
Model: 20RESA
(Based on expert analysis, manufacturer ratings and customer reviews)
4.1 out of 54.1 out of 54.1 out of 54.1 out of 54.1 out of 5
11 Reviews
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  • Features
  • Specs
  • 8
  • 11
  • Articles
  • Accessories
Run Watts
Rated Watts
120/240 Single-Phase

Product Video Disclaimer: "PED is not responsible for any variances from the product in this video and the item you purchase. Please review all product specs prior to purchase."

Commercial-Grade Kohler Command PRO® OHV Engine
Meets emission regulations for U.S. EPA & California
Powerful and reliable engine for heavy-duty applications

Powerful Performance w/ PowerBoost™ Technology
Greater motor-starting ability for large electrical loads

Premium Power Quality (+/-1% Voltage Regulation)
Protects sophisticated electronics with low distortion (<5%THD)

Fast Response
Kohler™ generators restore power in as little as 10 seconds

New Silencer Reduces Sound Levels & Provides Quiet Operation
Maintains neighborhood solitude - approx 69 dB(A) at 7 m (23 ft)

New RDC2 Controller
Glare-resistant, 2-line 16-character display - No More Codes
Easily view ATS status via LED lights on controller

Optional OnCue Remote Monitoring System (Sold Separately)
Built-in Ethernet card, no hardware needed for OnCue

Exclusive 100% Corrosion-Proof Composite Enclosure
Will not rust - even in harsh seaside environments

Premium Warranty - 5-year/2,000-hour limited warranty

Transfer Switch (Sold Separately) & Group 51 Bat. (Not Included)
Engine Brand
999 CC
Consumer Engine Warranty
5 Years
Commercial Engine Warranty
5 Years
Engine RPM
3600 RPM
Low Oil Alert/Shutdown
Product Specs
120/240 Single-Phase
60 Hertz
Surge Watts
20000 Watts
Rated Watts
20000 Watts
Fuel Type
LP/Natural Gas
NG Power Capacity
18000 Watts
LP Power Capacity
20000 Watts
NG Fuel Consumption @ 50% Load
161 (BTU: 161,000 BTU/HR) ft³/hr
NG Fuel Consumption @ 100% Load
281 (BTU: 281,000 BTU/HR) ft³/hr
LP Fuel Consumption @ 50% Load
2.3 (BTU: 208,725 BTU/HR) gallons/hr
LP Fuel Consumption @ 100% Load
3.9 (BTU: 353,925 BTU/HR) gallons/hr
Rated Amps
83 @ 240 Volts (Single Phase) Amps
Decibel Rating @ 7m
69 dbA
Transfer Switch
Automatic (Not Included)
Not Included (500 CCA)
A/C Ton Rating
Mounting Pad
Composite (Included)
Cooling System
Air Cooled
UL Listed
Grade Type
Made in USA
500 Pounds
Product Style
Standby Generator
Product Length
48 Inches
Product Width
26.2 Inches
Product Height
29 Inches
Consumer Warranty
5 Years
Commercial Warranty
5 Years
  8 Questions
Q: Does the OnCue require a hardwired ethernet connection?

And what is the purpose of the flex fuel line?

by Joe from New York on March 19, 2014

A: Yes, the OnCue system must be connected to your router via an Ethernet cable as it does not have wireless capability.

The Flex Fuel Line is required to prevent vibrations in the fuel piping which could cause the connection points to come loose or crack over time.

by Mike, Product Expert

Q: Hey Jim,
I thought only certified Kohler techs could start their generators in order not to void warranty.
And also is this Kohler RXT Series 400-Amp Outdoor Automatic Transfer Switch suitable with Model: 20RESA

by Franck Cathelot from Illinois on October 08, 2013

A: Thank you for your inquiry....

Any "certified" electrician can do a start-up on a Kohler generator. You do not need to have a Kohler tech do the start-up. The only difference is when the warranty starts.

When a certified electrician starts the generator the warranty starts the day the unit ships from Kohler and when a Kohler tech does the start-up the warranty starts the day the tech does the start-up.

Yes, you can use a 400A RXT switch with the 20kW Kohler unit as long as the generator has the output capacity to handle the load. We recommend using the Kohler LCM (Load Control Module) to help alleviate some of the starting loads.

Kohler LCM

by Mike, Product Expert

Q: What size gas supply pipe is needed from tank to generator?
by Richard Evans from Pennsylvania on July 20, 2013

A: Fuel pipe size is based on the distance from the fuel source and for the Kohler models the recommended pipe size and max distances are listed in the installation guide and in the Kohler spec sheet....

Kohler Spec Sheet

by Mike, Product Expert

Q: How does the warranty work? Does it have to be installed by a Kohler certified dealer for the warranty work?
by Franz Gerster from New York on December 13, 2012

A: Kohler does not require a Kohler certified installer only a minimum would be a certified electrician.

When a Kohler installer does the installation and start-up the warranty starts the day he starts the unit.

When a certified electrician installs and starts the unit the warranty starts the day the unit was shipped from the factory.

All service and warranty work must be completed by an authorized Kohler service technician.

by Mike, Product Expert

Q: Is the battery included with the unit?
by Darryl B from Louisiana on September 22, 2012

A: No, the battery is not included with the Kohler model 20RESA. You would need to purchase it locally. Most battery suppliers like Sears or Batteries Plus should carry it. You will need a 12 volt, 500 CCA (Cold Cranking Amp), Group 51 size battery.
by Mike, Product Expert

Q: How do I determine the amount of wattage needed for my house?
by Daniel Knepp from Michigan on March 10, 2012

A: Thank you for visiting Electric Generators Direct. In regards to your question, the generator size is determined by the starting amperage load of the equipment you are planning on powering when you lose power. The starting amperage load will be much larger than the running load and proper calculations need to be done to properly size a unit. We recommend having a certified electrician do your wattage calculations as every home is different. The electrician would calculate with the following formula to properly size the generator which should be sized at 80% of its running capacity to allow enough flexibility to handle large intermittent loads and still keep voltage output at proper levels. (Starting Amps x Volts = Watts).
by Mike, Product Expert

Q: Could you tell me how many BTU's this unit is? Thanks
by Christine from Ohio on February 28, 2012

A: The BTU's are listed on the spec sheet found on the generator product page under the specs link.

281 CUFT/HR @ Full Load (281,000 BTU/HR)
161 CUFT/HR @ 50% Load (161,000 BTU/HR)


by Mike, Product Expert

Q: Hi Jim,
What is the difference between the 20resl and 20resal?
I don't see the composite pad on this unit 20resal?

by Steve from New Jersey on February 21, 2012

A: The new "A" version has the following features added:
** New Controller - RDC2/DC2
- New display readable in direct sunlight, 2 lines, 16 characters per line, no more codes.
- Built-In 2.5A battery charger using 120 VAC allowing deletion of the separate 6A battery charger
- Includes Ethernet Board, so no hardware required to be installed for OnCue
- RDC2 has built-in LED's on controller overlay to view status of RXT transfer switch and source availability while standing at the genset
- Real Time Clock - Allows setting of Exercise for any time and day you want
- Internal protection, no controller fuses to service
- Controller is fully potted for protection against snow and moisture

** New Silencer design to reduce sound levels
- 14RESA sound level during exercise is 63 dBA, and 67 dBA during normal operation
- 20RESA sound level during exercise is 64 dBA, and 69 dBA during normal operation

The composite pad is the same color as the entire unit and already attached to the bottom of the generator.
by Mike, Product Expert

Kohler 20RESA Reviews & Ratings
Overall Rating
4.1 out of 54.1 out of 54.1 out of 54.1 out of 54.1 out of 5
Reliable (3)
Quiet (2)
Easy To Use (2)
Features (2)
Durable (1)
Unreliable (2)
Durability (1)
Heavy (1)
Low Quality (1)
57% of respondents would recommend this product to a friend
11 Reviews  Sort by 
Steve B.
Purchased from Electric Generators Direct
Purchased 9/25/12
Total Helpful Votes
20 Helpful Votes
5 out of 55 out of 55 out of 55 out of 55 out of 5
My experience with Electric Generators Direct has been fantastic. The service was extremely professional and timely. Jim was very helpful in confirming my equipment choice, and delivery was as promised and on time. The price of the generator went down after I sent in my order, but before it was shipped; Electric Generators Direct was more than happy to refund me the difference.

This is an extremely well run company.

The only thing better than dealing with you guys has been my Kohler... more
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Jacob S.
Woodmere, NY
Total Reviews
8 Reviews
Total Helpful Votes
252 Helpful Votes
5 out of 55 out of 55 out of 55 out of 55 out of 5
An Excellent 20kw Generator
Kohler 20KW Generator is an Excellent Whole House Generator. Quiet (Relatively for its class) It can power an entire house including central air conditioners. EGD offers the Best Price and the Fastest Delivery
View Image
Pros: Quiet, Price, Features, Reliable
Jacob Recommends This Kohler Product
Mike, the Generator Expert
Product Expert
Unfortunately, we cannot post this video…..the first generator may be closer than 5 feet from a window shown and the second generator is definitely less than 5 feet from the basement window.
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Dale O.
Vacherie, LA
Purchased from Electric Generators Direct
Purchased 5/30/13
Total Helpful Votes
17 Helpful Votes
5 out of 55 out of 55 out of 55 out of 55 out of 5
Good So Far, Didn't Have To Use It Yet
The only thing I am not happy with that Kohler don't honor the warranty unless you get a authorize dealer to come witness the start up. I called four defiant dealers and they wanted from $700.00 to $1000.00 to check it over and fill out warranty papers. If that's the case you shouldn't be able to buy them and install them yourself it should only come from a installed dealer.
Pros: Easy To Use, Quiet, Fast, Reliable
Dale Recommends This Kohler Product
Mike, the Generator Expert
Product Expert
I'm sorry that you got some wrong information. Either a certified electrician or a Kohler dealer. The main difference is that if a Kohler dealer does the start-up, the 5-year warranty begins on that day. If a certified electrician does the start-up, the warranty begins on the day it left the factory. Typically this is only a 1 month difference.
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Mike B.
Quemado, NM
Purchased from Electric Generators Direct
Purchased 8/15/12
Total Helpful Votes
14 Helpful Votes
5 out of 55 out of 55 out of 55 out of 55 out of 5
Stand-by Generator For A Remote Cabin
The Kohler 20RESA Generator is an excellent product. My cabin is completely off the grid and solar / wind powered. The generator is only used in the event of a system failure.

The mechanical design of the enclosure and particularly the systems connections are well thought out and easy to use. Periodic maintenance will be a snap thanks to the easy access filter and oil drain tube.

The system's remote start capability allows my power system controllers to determine when the generator is... more
Mike, the Generator Expert
Product Expert
We need to remind folks that off-grid use of stand-by generators will void the factory warranty; they are intended for use with standard electrical power installations only.
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Steven T.
Boca Raton, FL
Purchased from Electric Generators Direct
Purchased 7/9/13
Total Helpful Votes
11 Helpful Votes
2 out of 52 out of 52 out of 52 out of 52 out of 5
Installed & Ran For 2 Days Then Died
The control module was defective. Did initial start up and ran. Then got an error code on module and refused to run. Service tech deemed to be a faulty control board. Waiting now 2 weeks for replacement part from Kohler. Live in Florida and experience frequent power outages from FPL and hence the need for a standby generator. Right now, unit looks good and that is all. No word when the part will be available. Not a happy camper!
Cons: Low Quality, Heavy, Unreliable, Durability
Steven Does Not Recommend This Product
Mike, the Generator Expert
Product Expert
We apologize for the issues you're having with your generator. If there's anything else we can help you with, please contact us.
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Chad M.
Cream Ridge, NJ
Purchased from Electric Generators Direct
Purchased 11/2/12
Total Reviews
2 Reviews
Total Helpful Votes
16 Helpful Votes
4 out of 54 out of 54 out of 54 out of 54 out of 5
Top Of The Line, But Access To Warranty Service Is An Issue
I am very happy with my transaction from EGD, but I've had a couple issues with installation and service.

The unit is solid, generally well made, and well thought out. I really enjoy the OnCue system in particular.

The air intake access panel is impossible to replace once removed. I damaged it trying to put it back on, and I've been waiting weeks for Kohler's local distributor responsible for warranty service to respond.

12/7/12 After the heavy demands on the generator... more
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Mervin F.
Interlaken, NJ
2 out of 52 out of 52 out of 52 out of 52 out of 5
Kohler Composite Enclosures Crack
I have a 3 year old Kohler 20 kw Composite Home Standby Generator. I just noticed several cracks in the composite enclosure and although the generator has a 5 year warranty, there's only a 1 year on the composite enclosure. This should have been a red flag that the composite enclosures were junk. The fix will not be cheap, either a new generator or changing out the enclosure which would be a major undertaking.
Mervin Does Not Recommend This Product
Mike, the Generator Expert
Product Expert
I would suggest contacting Kohler directly or a servicing dealer. These composite enclosures have been on the market for sometime now and I'm unaware of any issues regarding them cracking.
Manufacturer Response
Brand Rep
We apologize for the issues you’ve experienced. Our customer service and field service teams have been working on this situation for you recently, and it is our understanding that you have been contacted by the Kohler field service supervisor, who was able to come to an agreement on a resolution for you. We will politely consider this matter to be closed at this time to mutual satisfaction.
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Myrna S.
Norman, OK
Purchased from Electric Generators Direct
Purchased 4/29/16
2 out of 52 out of 52 out of 52 out of 52 out of 5
Kolher Generators Are Good, But Has Its Flaws
I installed a 20kw single phase residential standby genset . Everything was great until I went to program the genset . The controller was bad, so next step is to see how well Kolher will do on taking care of the issue.
Pros: Can Not Comment On Gen It's Not In Working Order
Cons: Unreliable
Myrna Does Not Recommend This Product
Manufacturer Response
Brand Rep
We apologize for any issues you have experienced. We're not sure exactly what you mean by programming, as the RDC2 controller is factory-set, and should not require any programming adjustments outside of setting the date/time and weekly exercise. You can set the date/time by navigating to the "Date And Time" menu, and you can set the weekly exercise by navigating to the "Genset System" menu. You can also refer to the generator's operation manual for further details.

If you feel that your generator’s controller is defective, please contact a certified Kohler dealer for service support. You can find a list of certified service dealers by visiting our online dealer locator at, or contact us by phone at 1-800-544-2444 from 7 AM – 5 PM CT, M-F.

If your generator was not installed by a certified Kohler dealer, please also ensure that you register it in our warranty system by visiting
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Keith W.
Edmond, OK
Purchased from Electric Generators Direct
Purchased 3/28/13
5 out of 55 out of 55 out of 55 out of 55 out of 5
Worked Perfectly
The unit was delivered on time and in perfect condition. Got it all installed and the Kohler unit worked perfectly. I'm very well pleased with every aspect of the purchase.
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Edward R.
Kirkland, WA
Purchased from Electric Generators Direct
Purchased 6/21/14
5 out of 55 out of 55 out of 55 out of 55 out of 5
Great Generator
The generator was recommended by my electrician and is everything advertised. It works perfectly. Now, I am waiting for a storm.
Edward Recommends This Kohler Product
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New Orleans, LA
Purchased from Electric Generators Direct
Purchased 10/13/12
5 out of 55 out of 55 out of 55 out of 55 out of 5
Solid Performance
Purchased this generator after a passing hurricane knocked out power for 6 days. We vowed not to have it again. A year and a half later it finally had its time to shine. After a tropical thunderstorm knocked out power on a summer night, the generator performed flawlessly. It powered the entire house including two 3.5 ton A/C units.
Pros: Reliable, Durable, Features, Easy To Use
Bruce Recommends This Kohler Product
Bruce's Experience With Electric Generators Direct
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Shop for the Kohler 20kW Composite Home Standby Generator at Electric Generators Direct. Research Kohler 650531125569 standby generators air-cooled generator online. Find Kohler 20RESA standby generators air-cooled generator & Kohler propane natural gas operated generator system features and specifications.