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Generac Guardian™ 20kW Aluminum Home Standby Generator

Generac Guardian Electric Generators and Accessories
Model: 5887
(Based on expert analysis, manufacturer ratings and customer reviews)
4.8 out of 54.8 out of 54.8 out of 54.8 out of 54.8 out of 5
14 Reviews
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  • Features
  • Specs
  • 19
  • 14
  • 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."

Fully Automatic Operation When Paired With Nexus Smart Switch™

Generac OHVI Air-Cooled Engine
Features plateau honed cylinder walls and plasma moly rings
Full pressure lubrication system w/ 2 year oil change interval
Aids in cooling the engine for longer life

Operates On Clean Burning, Efficient Natural Gas or LP (Vapor)

Skewed Rotor Design For Smooth Output Waveform "Clean Power"
Automatic voltage regulator equipped for +/- 1% regulation

Nexus™ Digital Controller Monitors & Controls All Functions
Provides system status - compatible with Nexus™ wireless monitors

Sound Attenuated Weather Proof Enclosure
Attractive styling with lockable acess doors
Incorporates electrostatically applied epoxy paint technology
Sound dampening enclosure limits sound pressure to a low 66dB(A)
Matching fascia kit and 1' flexible fuel line included

Built-in Battery Charger (Battery Sold Separately)

Automatic Transfer Switch - ATS (Sold Separately)
Customize your system based on your actual application
Select the ideal ATS & DLM™ modules for load shed capabilities

Listed to UL2200 Engine/Generator Standard for Safety
Engine Brand
Generac OHVI
999 CC
Consumer Engine Warranty
3 Years
Commercial Engine Warranty
3 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
206 (BTU: 206,000 BTU/HR) ft³/hr
LP Fuel Consumption @ 50% Load
1.89 (BTU: 171,518 BTU/HR) gallons/hr
Rated Amps
83 @ 240 Volts (Single Phase) Amps
Decibel Rating @ 7m
66 dbA
Transfer Switch
Automatic (Not Included)
Not Included (525 CCA)
A/C Ton Rating
Mounting Pad
Composite (Included)
Cooling System
Air Cooled
UL Listed
Grade Type
Made in USA
451 Pounds
Product Style
Standby Generator
Product Length
48 Inches
Product Width
25 Inches
Product Height
29 Inches
Consumer Warranty
3 Years
Commercial Warranty
3 Years
  19 Questions
by DOUG FINLEY from Oklahoma on March 22, 2013

A: NFPA 37 Standards for the installation of stationary combustion engines and gas turbines, states that this distance should be at least 5 feet from any combustible material. Some local codes can be more strict so check with your local inspectors or AHJ (Authority Having Jurisdiction).

by Mike, Product Expert

Q: Could you tell me what size LP tank I would need for a 20kW Generac Home Standby Generator? Could I use two tanks or one big one?

by John Dimsdale from North Carolina on February 06, 2013

A: The minimum LP tank size recommended by Generac would be 200 Gallon depending on the ambient temperature in your area.

It is a good idea to contact your local LP supplier and let them know that you will be installing one of these units that have a BTU rating of 294,000 BTU/HR and they can help you properly size it based on your specific location.

by Mike, Product Expert

Q: Does the 5870 construction (enclosure make up) meet NFPA 37 condition 2 requirement?
by Bob from New Jersey on October 02, 2012

A: Subsection 4.1.4 of NFPA 37 reads as follows:

“4.1.4 Engines Located Outdoors. Engines, and their weatherproof housings if provided, that are installed outdoors shall be located at least 1.5 m (5 ft) from openings in walls and at least 1.5 m (5 ft) from structures having combustible walls.
A minimum separation shall not be required where the following conditions exist:

(1) The adjacent wall of the structure has a fire resistance rating of at least 1 hour.
(2)* The weatherproof enclosure is constructed of noncombustible materials and it has been demonstrated that a fire within the enclosure will not ignite combustible materials outside the enclosure.”

A4.1.4 (2) Means of demonstrating compliance are by means of full scale fire test or by calculation procedures.
Because of the limited spaces that are frequently available for installation, it has become apparent that exception (2) would be beneficial for many residential and commercial installations. With that in mind, the manufacturer contracted with an independent testing laboratory to run full scale fire tests to assure that the
enclosure would not ignite combustible materials outside the enclosure.

Per Generac Owner's Manual (All 8, 10, 14, 17 & 20kW Air Cooled Automatic Standby Generator):

The criteria was to determine the worst case fire scenario within the generator and to determine the ignitability of items outside the engine enclosure at various distances. The enclosure is constructed of non-combustible materials and the results and conclusions from the independent testing lab indicated that any fire within the generator enclosure would not pose any ignition risk to nearby
combustibles or structures, with or without fire service personnel response.

Based on this testing and the requirements of NFPA 37, Sec 4.1.4, the guidelines for installation of the generators listed above are changed to 18 inches (457mm) from the back side of the generator to a stationary wall or building. For adequate maintenance and airflow clearance, the area above the generator should be at least 4 feet with a minimum of 3 feet at the front and ends of the enclosure.
This would include trees, shrubs and vegetation that could obstruct airflow. See the diagram on the installation drawing within the owner’s manual on under the specs link for details.

Generator exhaust contains DEADLY carbon monoxide gas. This dangerous gas can cause unconsciousness or death. Do not place the unit near windows, doors, fresh air intakes (furnaces, etc.) or any openings in the building or structure, including windows and doors of an attached garage.

by Mike, Product Expert

Q: Do I need the battery to run the unit or does one come with it? Anyway, is it needed for it's operation?
by Woody from Georgia on August 11, 2012

A: A battery is required to start the generator at time of power loss. The unit does not come with a battery and one will need to be purchased separately.

by Mike, Product Expert

Q: What is the difference between the 5875 and the 5887?
by Joe DiPietro from Ohio on July 07, 2012

A: Joe, the 5875 basically includes the smart circuit automatic transfer switch, which you'll need to operate the generator.

The 5887 is just the generator - no transfer switch. It is usually purchased if you already have a transfer switch or if you need a different transfer switch for a unique installation.
by Mike, Product Expert

Q: Jim, what is the phone# where I can order a 20KW Generac propane generator w/transfer switch? Can I pay by check? Somewhere I saw "Save 2% by paying with check". Is this true?
by Fran Downing from Minnesota on May 08, 2012

A: You can either place your order online by adding item# 5875 to the cart and following the checkout procedure or contact customer support at 877-437-7998 and one of the CSR's can assist with placing your order. The following link takes you to the product page:

Model 5875

We do offer pay by check with a 2% savings, you would need to mail a paper check and when the check is received by our accounting department you will be notified via email.

From date of email notification we hold the order for 5 business days and then process and ship the order on the 5th day. See our check policy below:

Pay By Check Policy
by Mike, Product Expert

Q: How is the battery charged on these 20 kW air-cooled Generac generator? Does 120V need to be provided out to the generator in order to power a battery charger? Thanks!
by Tim Vitanza from Pennsylvania on January 30, 2012

A: The generator has a built in charger inside of the generators Nexus controller and when properly connected a 120V wire from the ATS (Automatic Transfer Switch) goes to the generator which provides the needed power for the internal battery charger.

by Mike, Product Expert

Q: What would cause the Generac 20kw guardian air cooled unit to fluctuate voltage under load?
by Brian from New Jersey on January 17, 2012

A: If the unit goes beyond the maximum of 82A the voltage can drop. The maximum surge amperage of the 20kW is 145A with a 30% voltage drop.

If you are having voltage issues well under the 82A range you need to have a Generac service tech inspect the unit.

Service Center Search

by Mike, Product Expert

Q: I've just ordered from you a 5887 w/out transfer switch but just noticed 92% buy the 5875 w/switch. I have a geothermal home that has a 50amp circuit breaker(uses 42amps). my electrician recommended the 5887. Could I use the 5875?
by Richard Ramondetta from Connecticut on January 14, 2012

A: The generators are exactly the same except that one comes with a switch and one does not. It really depends on if the generator has enough output to cover your Geo-thermal system "at start-up" and everything else you would have running on the generator at the same time.

Your electrician should be calculating your starting loads to verify what you can and cannot run. Plus the prepackaged system comes with a whole house type switch which may not work with your specific application based on your wattage needs with the Geo system.

by Mike, Product Expert

Q: Does this model have a built in battery charger?
by Don from New York on October 24, 2011

A: When properly connected to a Generac transfer switch the internal battery charger in the generator Nexus controller will keep the starting battery charged.

by Mike, Product Expert

Q: what size pipe for 20kw model 5875 connecting to lp or ng
by Mario Deramo from New York on September 27, 2011

A: Mario,

The 20kW unit has a 1/2" pipe connection but, the pipe run diameter is based on the distance from the fuel source.

Minimum pipe size - 1" - with max distance 20 ft
- 1-1/4" with max distance 130 ft
- 1-1/2" with max distance 305 ft

by Mike, Product Expert

Q: For a 20 KW nat gas unit which brand to you recommend and why? For use in Dallas. Thanks Jim
by Jim from Texas on August 19, 2011

A: I highly recommend the Generac model 5875 as Generac has the newest technology and the best engine in the industry with their OHVI Industrial engine. This engine is the only one that is specifically designed for generator use and is built in Wisconsin. The most environmentally friendly generator on the market - consumes less fuel and releases fewer emissions. Generac is the number 1 selling generator in the US.

Generac 20kW Model 5875

by Mike, Product Expert

Q: Jim I have a 100 amp Pre-Nexus service rated transfer switch. Can I use this with a nexus generator? Ive heard there is some special wiring for the battery charger to work
by Mike Noonan from Michigan on April 18, 2011

A: There is a special kit that needs to be added to the switch to accept the 120V connection which provides the power to the internal generator controller for the charger. These kits are available from your local Generac dealer - Part Number: 0H93030SRV.

by Mike, Product Expert

Q: How long can the 20kw propane generator run continuously?
by Alan Marcet from California on February 13, 2011

A: These units are designed for emergency back up to lost utility power and if you lose power for an extended amount of time these units can handle running for weeks if necessary. Please note that these units are not designed to run as a primary power source and if installed in this capacity the warranty will be void.

Generac does offer one primary power/off the grid type standby generator which is model 5818 and is specifically designed for extremely long run times.

Model 5818 EcoGen

by Mike, Product Expert

Q: How far does a generator has to be from my house?
by Jim from Massachusetts on February 04, 2011

A: The manufacturer recommends the back side of the unit to be set no less then 18 inches from any non-combustible surface and the sides of the unit need at least 36 inches for proper intake and exhaust.

Note: It is recommended to check with your city, county and state codes as they may differ from the manufacturers recommendations.

by Mike, Product Expert

Q: What are the BTU requirements for the Generac 20kW Standby Generators?
by Rich from Oregon on January 29, 2011

A: The BTU requirements can be found in the owner's manual which is listed in the specs tab. For the 20kW Generac Standby unit the BTU requirement is 294,000 BTU/HR.

Owners Manual

by Mike, Product Expert

Q: What kind of oil comes in the generator, and when it is time to change it? Can I run Mobile 1 Synthetic 5W30 year round in central Oklahoma?
by Ron Hopper from Oklahoma on January 24, 2011

A: The Generac standby generators are shipped with 5W30 oil in them and Generac does give the option to use 5W30 Synthetic in needed. The owner's manual covers all oil options and temperature ranges. Oil changes are determined by use and maintenance is also covered in the manual.

Owners Manual

by Mike, Product Expert

Q: I noticed that Kohler states you do not need a concrete pad when using their composite shell generator. My question is; does the same go for the Generac model 5875? Can the transfer switch that comes with model 5875 be substituted for a 100A transfer switch?

Thank you,


Acres Electric Corp.

by KEVIN BESANCON from Florida on January 21, 2011

A: Generac states that you can use pea gravel as a sufficient base for their standby generators 8kW to 20kW.

To be able to substitute the transfer switch Generac offers the generator alone under model 5887 and a suitable transfer switch can then be purchased separately.

Generac 5887

by Mike, Product Expert

Q: Hi Jim,
I live in Alaska and own a 5875 20KW Home standby Generac. I need to get a cold weather kit. I am looking at the Generac Cold Weather Kit for 14-20kW Home Standby Generators (992/999cc). First, is this the correct product for my generator and second, is it a "plug and play' install?

I understand I will need to change the oil to synthetic 5W30 so my guess is I'll need a maintenance kit as well. The generator has less than 3 hours on it.

Many thanks,

- Bill Thomson

by Bill Thomson from Alaska on January 21, 2011

A: That is the correct cold weather kit for the Generac Guardian 20kW model 5875 (or 5887) and it is a plug and play type unit, however, it is recommended by Generac to have a certified electrician install it due to the high voltage connection.

by Mike, Product Expert

Generac Guardian 5887 Reviews & Ratings
Overall Rating
4.8 out of 54.8 out of 54.8 out of 54.8 out of 54.8 out of 5
High Quality (1)
Reliable (1)
Price (1)
Easy To Use (1)
Heavy (1)
14 Reviews  Sort by 
Andrew L.
Saddle Brook, NJ
Purchased from Electric Generators Direct
Purchased 11/8/12
Total Reviews
2 Reviews
Total Helpful Votes
28 Helpful Votes
5 out of 55 out of 55 out of 55 out of 55 out of 5
Quality Business
As a electrical contractor with many instalations under my belt I highly recommend the 20 kW to take care of your power outage needs. Great service and delivery without any fuss. I have had units shipped to northern New Jersey with prompt reliable service. Thanks again as we continue to do business
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Pros: Easy To Use, Price, Reliable, High Quality
Cons: Heavy
Andrew Recommends This Generac Guardian Product
Andrew Would Recommend Electric Generators Direct To A Friend
Web Site


"By far quality service."
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5 out of 55 out of 55 out of 55 out of 55 out of 5
Works Perfectly!
I have had the system installed in my home for two years now. Several power outages later... No problems!

The system works just like it is supposed to work and electricity is restored to my entire home in 13 seconds! It handled two 4-ton air conditioners, two 3 HP pool pumps, two electric water heaters and many computers.

I did put the unit in a plastic building made by Suncast to protect it from the weather. See the photos.

I wanted to re-mount the transfer switch so that it... more
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Edward A.
Weddington, NC
5 out of 55 out of 55 out of 55 out of 55 out of 5
Home Owner
After extensive research, I purchased the Generac Guardian 20KW Home Standby generator. Two deciding factors were: 1. Generators are the only product of Generac and 2. The engine is pressure lubricated ensuring longer run life than splash lubricated generators.

Acting as my own general contractor, I hired a local electrician that I had experience with and knew could read the wiring diagram. The installation went without any problem. There was some initial confusion about the Heat Pump... more
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Purchased from Electric Generators Direct
Purchased 1/23/13
5 out of 55 out of 55 out of 55 out of 55 out of 5
Peace Of Mind
My contractor installed a 20kw Generac Generator for me. Timing was perfect as we discovered a gas leak at the gas meter. A new larger gas meter was installed including a new underground line to the street. I also had my contractor install a 200amp transfer switch in place of my old 200amp panel. Now it's all in one and totally automatic. When power goes out the generator response time is under 30 seconds. When commercial power comes back on the generator runs for an additional 60 seconds and... more
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Westport, CT
Purchased from Electric Generators Direct
Purchased 12/31/12
5 out of 55 out of 55 out of 55 out of 55 out of 5
Standby Generator Review
I'm very satisfied with this standby generator. No problems! Thank You
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Mark S.
San Francisco, CA
Purchased from Electric Generators Direct
Purchased 10/17/12
5 out of 55 out of 55 out of 55 out of 55 out of 5
Great Product But ...
I love the generator, the price, the great service and rapid delivery (beat the estimated time by a day) .

I think that this unit needs a simplified set up instruction sheet for the installer. I have installed in excess of 30 standby generator units but this one was the most confusing for a few simple reasons.

1. How to access the unit to install the battery - Lift the top, Remove the front panel by lifting up and pulling forward until the top anchor pins are clear then tip out and up... more
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Walter C.
Miami, FL
4 out of 54 out of 54 out of 54 out of 54 out of 5
Much Better
The 20 kv generator I installed is a replacement for a 15 kv generator that failed.

The 20 kv is operating much better and was an easy install; and the increased capacity is operating everything in my house where the 15 kv made it necessary to ration circuits.
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Purchased from Electric Generators Direct
Purchased 9/12/12
5 out of 55 out of 55 out of 55 out of 55 out of 5
Found What I Was Looking For
Just What I Needed!
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Titusville, FL
Purchased from Electric Generators Direct
Purchased 7/12/12
5 out of 55 out of 55 out of 55 out of 55 out of 5
First Florida Hurricane
Great price, it arrived within 5 days of placing my order, and was in great shape- just in time for our first hurricane.
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Jim Jones
Mcdonough, GA
Purchased from Electric Generators Direct
Purchased 5/21/12
5 out of 55 out of 55 out of 55 out of 55 out of 5
Works Like It Should, Customer Is Happy
We created a packed gravel base for it to rest and then hoisted it into place. It's much too heavy to manually lift. With a couple of trips by my electrician and one gas connection technician we were running as promised. My customer thinks we are brilliant and we just followed the directions provided by Generac. They're happy and so are we. I'll be back.
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David Miller
Phoenix, MD
Purchased from Electric Generators Direct
Purchased 2/2/11
5 out of 55 out of 55 out of 55 out of 55 out of 5
Good Price, No Sales Tax, Great Delivery & Product
We could not believe how well this order went. The generator was ordered on a Wednesday while your company was shut down because of the snowstorm. In spite of that it was shipped and we received the generator and transfer switch the first of the following week.

We had it hooked up and operational within a week with no problems. Good price, no sales tax, great delivery and product.
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5.0 out of 55.0 out of 55.0 out of 55.0 out of 55.0 out of 5
3 Reviews
 1   Q&A

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Shop for the Generac Guardian™ 20kW Aluminum Home Standby Generator at Electric Generators Direct. Research Generac Guardian 696471058871 standby generators air-cooled generator online. Find Generac Guardian 5887 standby generators air-cooled generator & Guardian 20KW liquid propane and natural gas operated generator features and specifications.