Our Briggs & Stratton 20,000 Watt Home Backup Generator Review

Power outages are a common problem in many areas of the country.  In some cases they last just minutes, and in others hours or even days. 

Having a reliable home backup generator allows you to continue to power appliances you need for both comfort and safety.  In this article we're going to review the 40396 standby generator from Briggs & Stratton.

The 40396 generator is designed from the ground up to be a solid backup power source for any circumstance. 

The industrial-grade Vanguard engine is capable of delivering 20,000 watts of power within seconds of a power outage, allowing you to rest easy knowing that you and your family will still be able to power your home in an emergency.


  • Relatively quiet
  • Highly reliable engine
  • Easy installation
  • Lots of Efficient Power


  • Large (cumbersome) transfer switch
  • Very heavy

Power When You Need It

While not everyone will need this much power the 40396 is capable of powering 2 air conditioning units as well as a whole host of other appliances in your home. 

It easily took first place in our best home generator comparison. (https://www.thetoolreport.com/home-generator-reviews/)

The generator package comes with a 2x200 Amp transfer switch. The transfer switch handles the seamless switch-over from using power from the power company to using your generator.

200A is large enough for most residential applications, but you'll want to calculate your total amperage just to be certain. The generator will sense when power from the grid is lost and automatically power up.

Once it's up and running, the transfer switch engages and you're now running your home from backup power.  In most cases this will happen in a matter of seconds.

Key Specifications

Voltage:  120/240 Single-Phase
Surge Watts: 20000 Watts​
​Rated Watts:  20000 Watts
Fuel Type:  Liquid Propane/Natural Gas
Natural Gas Power Capacity:  18000 Watts
LP Power Capacity:  20000 Watts
NG Fuel Consumption @ 50% Load:  187 (BTU: 187,000 BTU/HR) ft³/hr
LP Fuel Consumption @ 50% Load1.97 (BTU: 178,778 BTU/HR) gallons/hr
Weight:  484 Pounds
Product Length:  50.5 Inches
Product Width:  32.9 Inches
Product Height:  31 Inches

Once power is restored from the grid the unit will automatically shut down.​

Important Features and Performance

Briggs & Stratton's Symphony Power System is the brains behind the operation of this unit.  It regulates power usage in order to get the most out of every watt. This enables the unit to power multiple high wattage devices at the same time without overloading the unit.

This allows the unit to handle loads that would normally require a larger engine.  It's even capable of running 2 air conditioning units at the same time.  This is a big plus for those who live in the Southeastern U.S. and commonly lose power during the hottest months of the year.

The 40484 can run on both liquid propane or natural gas.  Liquid propane will require an on-site storage tank than can be buried on your property.  Natural gas requires natural gas service from a local provider.

If your area is prone to earthquakes liquid propane might be a more reliable source as an earthquake can damage gas lines and cut off your fuel supply when you need it most.

The Briggs & Stratton Vanguard motor is built to industrial specifications and is designed to last for thousands of operating hours.

This is not a consumer or prosumer grade engine.  It is built to industrial standards and is considered one of B&S's best engines to date.  The displacement is 993cc and it consumes 2.31 gallons per hour of fuel at a 50% load using liquid propane (187 ft3 /hr natural gas).

​Fuel consumption is as follows:

Natural Gas ft³/hr (m³/hr)

1/2 Load - 187 ft³/hr
Full Load - 260 ft³/hr

Liquid Propane (gal/hr)

1/2 Load - 2.31gal/hr
Full Load - 3.75gal/hr

The noise level is comparable to an idling car. Basically it's quiet enough that you and your neighbors should never hear it.

The unit comes with a 5 year warranty.

Installation & Setup

The installation of the unit is relatively straightforward.  A capable DIYer can handle most of the necessary work.  The unit comes with a metal mounting pad but will need to be installed on a level surface.  For this you can use concrete or pea gravel.  It's designed to be located as close as 18" from your house so it's very well suited to neighborhoods with smaller lots. 

The installation of the transfer switch should ONLY be handled by a qualified electrician.  This requires attaching the street power to the transfer panel and this is NOT something that should be taken lightly.

Since the unit comes with a dual transfer switch there is some basic configuration that must be completed during installation.  This is accomplished by setting the dip switches on the board to match the system you've put in place.  An electrician should be able to set this with no problem.

Briggs & Strattons Manuals

How Loud is the Generator?

The Vangaurd engine is designed to offer lots of power without a great deal of noise.  It utilizes a car-type exhaust and sounds about the same as a car at idle speed.  It's certainly noticeable from outside but you shouldn't be able to hear it from inside your home.

The unit is rated at 68.4dB

What Types of Fuel Does it Use?

The unit is designed to run on either natural gas or liquid propane.  Liquid propane requires an on-stie storage tank.

Does it Require Professional Installation?

Installation of the unit itself does not require a professional.  You'll need  level platform or concrete, pea gravel or other stable surface.

Installation of the transfer panel and all electrical hookups should be performed by a certified electrician. 

Final Thoughts

If you're looking for a solid, reliable home backup generator the 40396 from Briggs & Stratton is our top choice.  It offers TONS of power, flexible installation options, and comes with a dual 200 amp transfer switch. 

It's capable of running multiple air conditioning units without the need to utilize power shedding. 

The Vanguard engine is manufactured to industrial standards.  This goes well beyond most residential-type generators.  On top of that it's backed by a 5 year warranty.  For our money it doesn't get any better.

Inverter Generators

If you're looking for a smaller unit to power just a few of the essentials you should check out our inverter generator reviews here https://www.thetoolreport.com/best-generators/

One such unit is the Honda EU2000i which we reviewed in this article. https://www.thetoolreport.com/honda-eu2000i-inverter-generator-review

About the Author Jason Thompson

Jason is a work from home dad who has a passion for DIY projects, yard work, and SEC Football. His background is IT, but he's always fancied himself as a part-time ship welder, landscaper, and short order cook. During the week he can be found on his laptop 10 hours-a-day, but on the weekends he escapes to the local DIY Cave to play with REAL toys.  You can also find him on Facebook, Twitter, and can contact him via email.