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Generac Guardian 5875 20kW Standby Generator (Aluminum) Pre Packaged 200 Amp Service Rated ATS

Generac Power Systems Generac Power Systems
Model#: 5875
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Generac Power Systems 6212 Details and Specifications

The Generac Guardian Series of standby generators are designed to start and operate automatically during a power outage. The Generac Model 5875 package is a popular standby generator with a Nexus Controller sold by Norwall Power Systems and includes a 20-kilowatt generator packaged with an 200 amp, service-entrance-rated automatic transfer switch.

Fuel choices

All Guardian generators operate on either natural gas or on LP gas. Availability and cost are the main factors in choosing between the two fuels, but the fuel choice also affects the power output of the generator. The 5875 can produce a continuous 20 kilowatts of power using LP gas, but that is reduced to 18 kilowatts for natural gas. Fuel consumption at fifty percent load runs about 1.9 gallons per hour for LP gas and 2.9 gallons per hour at full load. Natural gas use is 206 cubic feet per hour at half load, and 294 cubic feet per hour at full load.


The engine is Generac's own overhead valve industrial engine; the only engine designed specifically for use in a generator. The design of the V-twin, 999 cc engine allows for extended operation with an extended maintenance cycle twice that of most generators. It runs cooler and smoother with less vibration and easily switches from natural gas to LP gas in the field.

The engine senses low oil levels and shuts itself down to prevent damage. Pressurized lubrication helps keep the engine operating smoothly and for extended periods without interruption.

Transfer Switch

The Generac Nexus Smart Switch is a UL rated, automated transfer switch that handles the changeover from utility power to the standby generator in the event of a power outage and incorporates load management for high demand appliances. The switch is normally mounted close to the existing service panel for ease of access, installation and convenience.

The Smart Switch incorporates load management for high demand appliances through a load-shedding controller and manages one or two air conditioners without additional equipment, and up to four additional high demand appliances with the addition of Demand Load Management modules.

Nexus Controller

The Nexus Controller is an integral component of all Guardian generators and manages generator functions. Once a week it starts the 5875 generator and exercises it for 12 minutes. When the generator is not in use, the controller monitors and charges the battery to ensure it is ready when needed and alerts the owner to replace the battery when it will no longer hold a charge.

When a power outage occurs, the controller senses the outage and waits to ensure it was not a momentary interruption, then starts the generator after ten to thirty seconds (programmable). During operation, it monitors generator voltage continuously and adjusts it for utility quality power, and also controls the frequency to keep it at a steady 60 hertz. When utility power is restored, the controller instructs the transfer switch to change back to utility power, but continues to operate the generator in a cool-down mode for up to one minute before shutting it down.

The controller also senses incorrect/improper wiring to alert the user and prevent damage to the system. If the any part of the system shuts down, it can notify the homeowner through a general alarm displayed on the generator control panel. The optional advanced wireless remote controller sounds an audible alarm if a malfunction is detected.

Generator Unit

The alternator or generating unit is the heart of the system that produces electricity. It utilizes an efficient revolving magnetic field and a stationary armature with skewed stators that keep the current output smooth, clean, and free of spikes and noise. The unit employs automatic voltage regulation for continuous, unvarying power and also helps to provide for the momentary high inrush currents required by electric motors during startup.

Appearance and Noise

The overall appearance is clean and unobtrusive, with a smooth, protective case. The entire unit stands 28 inches tall, 47 inches wide and 25 inches deep. The aluminum cabinet resists rust and is covered by epoxy paint for a long lasting finish. The engine's muffler is located within the cabinet to guard against burns and injury and keeps the generator's noise level to 66db or lower. The 5875 package includes the fascia and trim kit normally sold as an accessory.

20kw Generac Generator 5875 Includes:

200 Amp Service Rated Nexus Smart Switch with Digital Load Management Technology Nema 3R Rated #RTSD200A3, Flexible Fuel Line Connector, Composite Mounting Pad, Base Fascia
USA Engineered & Built

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Product Specifications

Model Number 5875
Manufacturer Generac Power Systems
Made In USA Yes
Rated Watts 20 kW
Rated Amps 83LP/75NG
Voltage 120/240V Single Phase
A/C Ton Rating 5 Tons
Enclosure Aluminum
UL Listed Yes
Decibel Rating 66 db(A)
Starting System Electric/Automatic
Low Oil Alert Yes
Idle Control No
Hour Meter Yes
Battery Requirement Requires 12Volt, Group26R-525CCA
Mounting Pad Composite (Included)
Product Weight 451 lbs.
Dimensions (Inches) 48L x 25W x 29H
Engine Brand Generac
Engine Size 36 HP/999 cc
Engine RPM 3600 RPM
Cast Iron Sleeve Yes
Cooling System Air Cooled
Alternator Type Brushed
Frequency 60 Hz
Auto Voltage Regulation Yes
Fuel Type LP/NG
NG Power Capacity 18kW
LP Power Capacity 20kW
NG Consumption @ Full Load 294 cu.ft/hr
NG Consumption @ 1/2 Load 206 cu.ft/hr
LP Consumption @ Full Load 2.90 gal/hr
LP Consumption @ 1/2 Load 1.89 gal/hr
Transfer Switch
Transfer Switch Model RTSD200A3, Nema 3R, Outdoor
Transfer Switch Amps 200 Amps
Transfer Switch Circuits Whole Panel, Service Entrance Rated, Nema 3R, Outdoor Rated
ATS Poles 2 Poles
Warranty Information
Consumer Warranty 3 Years Limited
Commercial Warranty 3 Years Limited
Shipping Weight 572 lbs
Shipping Dimensions 45H x 50W x 27D
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Product Reviews

Showing reviews 1-10 of 44 | Next

  1. Outstanding unit. Power to spare

    Posted by Bobby on 31st Aug 2013

    Bought unit in May 2013. Then completed install and the power went out 3 days later. The unit picked up load and never skipped a beat.

  2. Power to spare

    Posted by Patrick on 15th Mar 2013

    Just received my 20kw generac in less than a week after ordering. Very well packaged and the curb service worked well. Opening the generator door was like looking under the hood of a new car. My next step is to finish the installation and then put it to the test for the next power outage. Should have plenty of power to spare.

  3. I feel so much better no more fears of bad weather

    Posted by vincent c on 1st Feb 2013

    I was with no power for a week during hurricane sandy and it was the worst experience of my life, This will be the best investment I have ever made in my life. Thank you for being there norwall when I needed you most.

  4. Never without Power Again!

    Posted by Aaron on 30th Jan 2013

    We sold our home old house in 2011 and left our 17kw at our old house. Of course this past year has been brutal for storms and power outages! You never miss what you had until need it. I now know what my old neighbors felt when they had NO power for over a week and I didn't miss a beat with my old Generac generator...Never again....Piece of mind once again...don't hesitate...

  5. Peace of mind that you will not be left in the dark!

    Posted by Jennifer H on 11th Jan 2013

    My husband and I purchased this packaged unit and we love it! We had a 3 day power outage recently and it started up and worked exactly the way it was supposed to. We have four children and to lose power (especially in the winter) is unimaginable! Now we have peace of mind that we will not have to leave our home during a bad storm. Love it!!

  6. My 20kw generac unit is my first choice in power!

    Posted by phillip r on 10th Jan 2013

    My secound choice is my 15 kw generac portable generator i bought in 2005.This 15 kw system was purchase for the katrina hurricane.I wanted a total automatic power system after i retired, so i purchase the 20 kw generac generator from norwall power systems.I know about the quality from experience!

  7. Power when you need it!

    Posted by Ted T on 2nd Jan 2013

    I purchased the Generac GUARDIAN Standby Generator – 20KW Model# 5875 in 2010 following our last power outage, courtesy of Hurricane Irene. This year we were hit by tropical storm Sandy and once again we lost power, for about 15 seconds, that’s when the generator kicked in, automatically. We had enough electricity to share with our neighbors. If it wasn’t for Generac, we would have been without power for 4 days. One of my best purchases ever.

  8. I love this product

    Posted by Unknown on 25th Dec 2012

    We installed this on Saturday and our electric went off on Thursday and everything worked perfectly. It seemed strange to look out at our neighbors and everything else is dark,but nice


    Posted by TOM M on 20th Dec 2012


  10. So far so good

    Posted by John on 20th Dec 2012

    Ordered my 20kw right after Sandy hit. I was fortunate enough to purchase one here at Norwall that was in stock at the time, and therefore, it arrived shortly thereafter. Had to have propane installed and after that was completed, the electricians came along and installed the generator. They demonstrated how it will turn on by shutting off the power to my house. All I can say, is it is a great feeling to see your home come back to life approximately 10 seconds after the power is off. As far as noise, it honestly isn't much at all...probably like a push mower in terms of levels of sound...so nothing that will upset neighbors. At this point, no power outages yet, but I am looking forward to the next one!

Showing reviews 1-10 of 44 | Next