Generac Guardian 20kW Standby Generator Pre Packaged 200 Amp Service Rated ATS 6244
Generac Power Systems

The Generac Guardian Series standby generators are designed to start and operate automatically during a power outage. The 20kW Generac 6244 package is a popular standby generator that uses the integrated Evolution 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 6244 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 2.0 gallons per hour for LP gas and 3.9 gallons per hour at full load. Natural gas use is 205 cubic feet per hour at half load, and 308 cubic feet per hour at full load. Required fuel pressure to generator fuel inlet at all load ranges 3.5" - 7" water column for natural gas or 10" - 12" water column for LP gas.


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 Automatic Transfer 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 Automatic Transfer 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 Power Management Modules(PMM).

Evolution Controller

The Evolution Controller is an integral component of all Guardian generators and manages generator functions. Once a week it starts the 6244 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 2-1500 seconds (programmable by an authorized Generac dealer, default start is 10 seconds). 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 Evolution 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. The Mobile Link allows remote monitoring of generator status via web, email or texts.

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. Certified for 18” Installation to the home (3rd Party-certified to NFPA standards provided it is located away from doors, windows and fresh air intakes, and unless otherwise directed by local codes.) The entire unit stands 29 inches tall, 48 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 6244 package includes the fascia and trim kit normally sold as an accessory.

20kw Generator by Generac 6244 Includes:
200 Amp Service Rated Automatic Transfer Switch with Digital Power Management technology (DPM) Nema 3R Rated #RTSY200A3, Flexible Fuel Line Connector, Composite Mounting Pad, Base Fascia

USA Engineered & Built


Generac Guardian 20kW Standby Generator Pre Packaged 200 Amp Service Rated ATS 6244

Generac Power Systems Model #6244
This product is no longer available for purchase.
To see the product that replaced this model or one
similar in specifications click on the button below.
Country Living
Comment by Jim C. on 9th Nov 2014

My Mom and Dad are both in their 80's and live in the country. With the installation of the 6551 I can rest assured that they will never be without power, heat, ac and water. this is a great unit and worked perfectly upon startup. Should have installed this a lot sooner for them.

By the way, my son-in-law also has one for his home. I live in a motorhome or I would have one also.

Read More Customer Reviews