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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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Maintenance Kits, Replacement Parts & Accessories

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

Generac $50/$50 Referral Rebate, Click Here

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

Previous | Showing reviews 31-40 of 44 | Next

  1. Best Generator Ever

    Posted by Charlie T on 18th Jan 2012

    I bought the Generac guardian Standby Generator Model# 5875, 20,000 Watts, 200 Amp Service Entrance, in September of 2010 in preparation for the hurricanes about to come. We were hit by Hurricane Irene and lost power for 5 days. I cannot tell you how blessed we feel for having this generator in time for the storms. It was a life saver. Without our assistance, the generator switched on just as the power went out for our entire street. We had a few family members come stay with us until their power was restored. We are now purchasing one for our parent?s home because at their age they need to feel as safe and comfortable as we did. I would recommend this to everyone. Ted Powers

  2. Satisfied customer

    Posted by Philippe A on 10th Jan 2012

    The generator I wanted was on backorder so. I was disappointed about the wait, but Norwall kept me very informed about the status of the order and got it in as fast as they could. The Generator was delivered in good shape and to this day we are very happy about our purchase.

  3. Happy and I know it

    Posted by Justin J on 14th Dec 2011

    My experience with Norwall PowerSystems was positive from the beginning. Their customer service reps were very knowledgeable and friendly. I received my Generac generator two weeks earlier than expected and the shipping vendor was very accommodating. The generator was in perfect condition when delivered.

  4. Recommendation is key

    Posted by Joe Clair on 11th Dec 2011

    I had done a lot of online research on the product that I ordered and Norwall PowerSystems came highly recommended. However I was very surprised when I ordered a generator on Sunday and it was delivered on Wednesday morning. Very good service! Lucky for us it was delivered right before an ice storm. All of the power was knocked out on our street except for us and the people beside us. We chose this generator in the end because of its fair price, ATS was included and it manages up to whole house backup if we need that in the future.

  5. First time is a charm

    Posted by Matt LeGrace on 10th Dec 2011

    This is my first time buying a generator. This website has been extremely resourceful with information and a search box assisting me in choosing the right generator for our family. Also, these guys are the cheapest on the web!

  6. owned for 6 years & never had any problems to fix excluding general maintenance

    Posted by david g on 4th Dec 2011

    This is the only way to go. Cheapest price no tax, free shipping. Compare & you'll see for yourself.

  7. Best investment I've ever made

    Posted by Stan S on 24th Oct 2011

    I live in community with lots of trees, ergo lots of power outages during strorms. Have owned a Generac portable for about 10 years and it has given flawless service, hence my decision to go with a Generac whole house generator, after my bride of 41 years decided she needed hot water during our frequent outages. Norwall is an outstanding company with great prices and great customer service. I couldn't be happier with my Norwall experience and now recommend then to all of my neighbors also considering moving up to a whole house generator.

  8. Best Standby Generator

    Posted by Brian on 19th Oct 2011

    This generator has been a lifesaver. It's quiet, reliable and fairly inexpensive compared to other brands. We installed this one day and had a power outage the next. The outage lasted about 6 hours and other then a 30 second delay to allow it to start, I had power the whole time my neighbors were out. You don't even have to worry about when it comes back on, because you won't hardly even see a blink of the lights when it changes back to utility power.
    If your on the fence about generators, go with Generac, you won't be disappointed.

  9. After Irene

    Posted by Dick Healy on 26th Sep 2011

    After hurricane Irene came and went we lost power for two days. After this experience my wife and I looked into a whole house emergency system, we settled on Generac 20kw with the integrated control box, Norwall Powersystems was by far the best price. I ordered this unit on a Saturday evening and it was delivered 3 days later by ups in perfect condition. We had the unit installed by the electrician who wired our house when it was being built, 4500 sq. ft. 4 bdrm's 4 bath's freezers , refrig, and a entertainment room the generator was installed gas co. provided the gas and the first test the system worked flawlessly, when my electrician cut the power the generator came online within 7 seconds and powered my whole house, 2 a/c units and everything else w/o hesitation. Let it RAIN!! Onto for the rest of the report, a handyman around the house guy like I am can not hook this up and get the proper desired results it is better left to a pro, Cost approx 1,000.00 but well worth the end result, if you already have ng or propane you have less cost, I had none of the above so cost was 600.00, but in the long run the first time this thing comes on line these issues will be completely forgotten.To end I highly recommend Norwall & Generac I hope this helps someone

  10. I primarily bought the generator for peace of mind following the remodeling of my basement.

    Posted by Mike Beier on 1st Sep 2011

    I’ve had my Generac (20kW with 200 Amp Automatic Transfer Switch) for approximately 2 years now. I run the unit on propane fuel which required me to purchase a propane tank. I put a 250 gal tank behind my barn which I now also use to run a propane furnace for heating the barn in the winter. I primarily bought the generator for peace of mind following the remodeling of my basement. The last thing I wanted was to loose power to my sump pump and have the basement flooring damaged. Since installation, I have lost power several times from a few minutes to several hours. With each power loss the Generac came on and transferred my loads with out error each time. The weekly test run that the generator goes through additionally provides me with the added assurance that when called upon I can be guarantee d will perform flawlessly. I have a geothermal heating/cooling system and the 20kw unit has no trouble carrying the load. This is an excellent generator that I would recommend for anyone looking for a whole house unit.

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