Message to Our Customers


Model # 6729

Internet # 205399532

20,000-Watt Air Cooled Automatic Standby Generator with 200-Amp SE Rated Transfer Switch

This item has been discontinued.
The Home Depot no longer carries this specific product.

$4,499.00 / each


Model # 6729

Internet # 205399532

Store SO SKU # 1000640155

Choose the #1 Selling Home Standby Generator Brand. Generac’s 20kW Guardian Series provides the automatic backup power you need to protect your home and family during a power outage. Connected to your existing LP or natural gas fuel supply, it kicks in within seconds of determining power loss automatically and runs for as long as necessary until utility power returns. Control your power. Control your life.

  • Your Guardian series generator might have to get you through days or weeks without utility power, Generac’s OHVI engine, specifically designed for generator use, provides the reliability to power through the most severe outages
  • True Power technology provides best in class power quality with less than 5% total harmonic distortion means clean, smooth operation of your sensitive electronics and appliances
  • The evolution controller is the next generation of intuitive controllers featuring a multilingual, 2 line LCD text display with color-coded, backlit buttons
  • Third party certified to NFPA standards to be installed as close as 18 in. from the home’s exterior wall, provided it is located away from doors, windows, and fresh air intakes, and unless otherwise directed by local codes
  • When combined with a Smart Switch, re engineered connection points, and composite mounting pad that eliminates the need for a poured concrete base (unless specified by local codes), the guardian series 20 kW generator is easy to install
  • In areas with low natural gas pressure, the Guardian series 20 kW generators can operate on natural gas pressures of only 3.5 in. of water column
  • Our durable powder coat finish helps make the sturdy, galvanneal steel enclosure perfect for all weather conditions, it’s also able to withstand 150 MPH winds
  • Switch between natural gas and LP fuel in the field in a few seconds, without the need for any tools
  • Thanks to Quiet-Test, your Guardian series home standby generator runs its weekly self test at a lower RPM for only 5 minutes, it’s quieter than other brands, and consumes less fuel, choose your schedule weekly, bi-weekly or monthly
  • Take advantage of Generac’s mobile link cellular remote monitoring system and check on your generator’s status using your computer, tablet or smartphone, even when you are away, sold separately
  • Power outages don’t always occur during normal working hours, that’s why Generac’s customer care call center right here in Wisconsin provides support any time of day or night, all year long, Generac is standing by 24/7, every minute of every day, to answer your questions
  • 5-year limited warranty

Info & Guides

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Height (in.) 
Product Depth (in.) 
Product Height (in.) 
Product Length (in.) 
Product Width (in.) 
CA (CARB) Compliant 
CARB Compliant 
Color Family 
Commercial / Residential 
Continuous Wattage 
Engine Displacement (cc) 
Engine Make 
OEM Branded 
Hour Meter 
Low oil shutdown 
Operational volume (dB) 
Product Weight (lb.) 
451 lb 
Remote Monitoring 
Sold Separately 
Response time (sec.) 
Warranty / Certifications
Certifications and Listings 
1-UL Listed,CSA Listed 
ENERGY STAR Certified 
Manufacturer Warranty 
5 Year Limited 


Rated 4.8 out of 5 by 298 reviewers.
Rated 5.0 out of 5.0 by This is our second one - great generator!! We recently moved into a new home and purchased this 20KW Generac. After installation the electrician threw the power to the house and the generator automatically transferred power with natural gas. We haven't had a power outage since it was installed but it is a great peace of mind knowing that our home can still function as usual during an outage. It automatically runs an exercise every week. We don't notice the noise when we are inside. We knew that we wanted this brand because our old home had the 17KW which never failed us. Found the best pricing at Home Depot. November 6, 2013
Rated 4.0 out of 5.0 by The generator is only part of the cost I think the Generac will be good to have, but you should be aware that the installation costs may be more than you expect. I had to get a larger capacity gas meter for $150. The gas plumber was $700 and the electrician will be $1200-$1500. Probably still worth it because we've been flooded out 4 times before due to power outages and each time cost more than the generator will cost. August 27, 2013
Rated 5.0 out of 5.0 by MY 2ND GENERAC STANDBY 20KW GENERATOR FROM HOME DEPOT IN 7 YRS/THIS 1 FOR OUR NEW HOUSE MY OPINION AND EXPERIENCE: My 2nd standby Generac 20KW Nat gas generator. Even better. My 1st had to have a concrete pad/separately ordered transfer switch, is water cooled with a Mitsubishi engine. This 1 is air cooled on it's own composition pad and CAME with the transfer box/switch. I have yet to use it in a power outage. The driver was able to back his rental delivery truck to the unload area and place it by the house where it is now installed. Besides saving me money, and getting a policy adjustment as it went on sale online/price match, free delivery to it's installation place saved me on installation. The company that installs here did not have to pick it up and set it in place! Living here in hurricane country and thunderstorm territory in the far burbs this is a must have! After hurricaines Ivan/2004 and Katrina/2005 it is dangerous to hunt gasoline for a small generator daily, and we are too old to do without our conveniences. Then there is security if you go to a hotel if you can find one. An empty house invites looters. I will gladly pay the gas bill, equate it with those mentioned expenses of hotel and security. You can use the large propane tank if you don't use natural gas. I do recommend getting a maintenance contract with a local generator maintenance company. Those contracts go year to year to change oil, check maintenance, your system, replace the battery when needed, etc. I use synthetic oil when they change the oil, lasts longer! The machine should be set to run a bit same time once a week, charge the battery and keep moisture out of the machine to keep it in good running order. We have ours set for Sunday mornings. I highly recommend HOME DEPOT and their special financing credit card offers on these! July 10, 2014
Rated 5.0 out of 5.0 by Just as Advertised! Installation with a my Certified Electrician $700. Installation time 5 Hours. Transfer Switch works great. I Installed Advanced Wireless Generator monitor. It too works as promised. The only thing this generator needs is a smartphone app that does not charge a monthly fee. October 1, 2013
Rated 5.0 out of 5.0 by Works like it is supposed to I purchased this product and have had it installed. Total cost of installation was $1,200 for electrician and permit ($250). The propane company installed a tank, put a 40 foot line in and delivered 100 gallons of propane for $600. The unit works just like it is supposed to work When the power drops out, the unit waits approximately 10 seconds, starts itself, and about 10 seconds later, it picks up the load of the entire house. conversely, when the power returns, the unit stays on generator power for about 10 seconds before it switches back to utility power. It then runs the generator for about 60 seconds to cool the unit and then shuts off again. June 5, 2013
Rated 5.0 out of 5.0 by This product was everything I wanted it to be. My wife and I were very concerned about electrical blackouts and wanted an affordable solution to this problem. We shopped around and talked with various electrical contractors and even found one that we selected to do the installation. He recommended his own brand, stating that it was the best. However we selected the Generac Guardian Series 20,000 based on reviews, product description and price. Home Depot worked with us and made the purchase very affordable. When installed, the electrical contractor said he was very pleased and found it to be as good (or better) than the one he had recommended. Luckily we have not had to use the system yet, but it is set up for weekly self testing and the electrical output is more than adequate for our entire home and it works in test mode like a dream. I am trying to decide now if I want a real blackout just so that I can gloat over my neighbors. June 19, 2013
Rated 5.0 out of 5.0 by Attractive design, quiet operation and great features especially fuel conversion, NG > LP Unit was self installed. Installation/users manuals well written. Generator & Transfer Switch connections well labeled. LCD control panel very user friendly for setup. Ease of NG>LP fuel conversion perhaps best feature. December 11, 2013
Rated 5.0 out of 5.0 by Great piece of mind purchase! Although I have yet to have a outage since installment, I feel confident that my unit will kick in and power my whole house. We had an outage the week before I had my unit wired and plumbed in that lasted 36 Hrs. Wish I had gotten it done sooner. Here are a few things I learned, hirer a electrician! I'm a mechanic by trade but after seeing the way the electrician did the wire install I was amazed. I'm sure my install would not been as nice or reliable? The plumbing is pretty straight forward. I have my unit in a remote (cold) location and they recommend a cold climate kit. Have your electrician rewire the 110 outlet inside the generator cabinet to the house power. Then buy on line a battery heat blanket a long with a 75 watt engine oil pan heating pad. They also sell on line a thermostat 110 volt outlet to plug the 2 heat elements into. You can buy the 3 pieces on line for about half of the recommended kit. I have a 200 watt service panel in my house and the unit comes with a 200 watt transfer box but the generator only has 100 watt service breakers. No problem as long as you don't have every electrical unit in your hose turn on at the same time.(every light, A/C, Furnace, hot water heater, well pump, etc) If you do the only problem is that you will pop the 2-100 watt service breakers in the generator. February 13, 2012
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