Briggs and Stratton 48 kW Fortress Standby Generator

Liquid-cooled, emergency-grade backup power that starts automatically in seconds (Auto Transfer Switch required)

If you are backing up a large home, a multi-building property, or a light commercial site, you need more than a typical air-cooled standby generator. The Briggs and Stratton 48 kW Fortress is a liquid-cooled, emergency-grade standby generator built to deliver serious power with stable voltage for modern electronics, quieter 1800 RPM operation, and a warranty that takes a lot of stress out of ownership.

This is the kind of system you install once and count on when storms, outages, and grid issues show up at the worst time.

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What the Fortress 48 kW does when the power goes out

With an installed automatic transfer switch (ATS), the Fortress system:

• Detects utility power loss
• Starts automatically within seconds
• Transfers your building to generator power
• Monitors utility restoration
• Transfers back to utility power when it is stable

No manual steps. No cords. No late-night scramble.

Important: This generator requires an automatic transfer switch. Transfer switch not included.

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Big, steady power for real-world loads

48,000 watts of standby output

• Rated output: 48,000W
• Single-phase output: 120/240V
• Rated amps: 200A
• Frequency: 60 Hz

That level of output is designed for larger electrical demands where you want strong coverage across critical loads and comfort loads, not just a few circuits.

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Liquid-cooled 4.3L 6-cylinder engine at 1800 RPM

At the heart of the Fortress is a 4.3L industrial 6-cylinder liquid-cooled engine running at 1800 RPM.

Why that matters:

• Lower RPM operation supports better long-run durability than high-RPM standby units
• Liquid cooling helps maintain stable operating temps during extended outages
• Quieter operation for its class, especially compared to high-RPM designs

This is a serious engine platform built for standby reliability.

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Runs on natural gas or propane

The Fortress 48 kW can be configured for natural gas (NG) or liquid propane (LP):

• Connect to your home’s NG supply, or
• Connect to a properly sized LP tank

Fuel planning is a major part of any large standby setup. Here are the published consumption numbers so you can plan line sizing and storage correctly.

Fuel consumption

Natural Gas

• 50% load: 328 ft³/hr
• 100% load: 511 ft³/hr

Propane (LP)

• 50% load: 3.68 gal/hr
• 100% load: 5.82 gal/hr

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Clean power for sensitive electronics

Today’s homes and businesses have a lot of expensive boards and devices that do not like unstable power. The Fortress includes a computer-friendly brushless alternator with automatic voltage regulation, helping protect:

• Network gear (modems, routers, access points)
• Computers and office equipment
• Security systems and cameras
• Smart appliances and modern HVAC controls

Clean, regulated output matters just as much as total watts.

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Smarter control with the Briggs and Stratton AMF Controller (UL Recognized)

The built-in AMF controller gives you visibility and control without making things complicated:

• Easy-to-read alpha-numeric scrolling display
• Monitors diagnostic conditions
• Displays fault codes
• Simple weekly exercise-cycle scheduling

You get the confidence of knowing the unit is ready and the clarity to troubleshoot quickly if an alert appears.

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Built for weather, built for service

Corrosion-resistant aluminum enclosure

The enclosure is designed to hold up in harsh climates and protect the generator from extreme weather.

Convenient service access points

Routine maintenance should not require unnecessary disassembly. Service access points are designed to reduce service time and hassle.

Pre-installed block heater

Cold starts can be where standby systems struggle. A pre-installed block heater supports easier cold-weather starting and more consistent performance.

Turnkey extras included

This unit includes:

• Automatic battery charger
• Block heater
• Hour meter

Less piecing together. More ready-to-run.

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Sound level and physical specs

• Noise level: 67 dB at 7m
• Weight: 1,635 lbs
• Dimensions: 91 in L x 39.4 in W x 41 in H
• Enclosure: Aluminum
• Cooling: Liquid-cooled
• Circuit breaker size: 200A
• UL listed: Yes
• CARB compliant: Yes
• Made in USA: Yes
• Grade type: Emergency

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Requirements (do not skip these)

To install and operate as designed:

• Automatic transfer switch required (not included)
• Requires 775 CCA starting battery (not included)
• Concrete mounting pad required (not included)

This is a heavy, high-output standby generator. A professional installation is standard for safety, code compliance, and proper fuel delivery.

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Warranty

• Consumer warranty: 6 years
• Commercial warranty: 2 years

The 6-year coverage includes parts, labor, and travel, which is a major advantage for a generator in this size class.

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Best fit uses

The Fortress 48 kW is a strong fit for:

• Large homes with significant electrical demand
• Properties with multiple critical systems (security, networking, pumps, refrigeration)
• Light commercial buildings that need reliable standby power
• Farms and ranches that cannot afford downtime

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Bottom line

The Briggs and Stratton 48 kW Fortress is a high-capacity, liquid-cooled standby generator built for automatic backup power, clean output for sensitive electronics, and long-term confidence backed by an industry-leading warranty. If you want a serious standby system that starts fast and runs steady, this is the right tier of equipment.

Resource

Manuals:

Generator Sizing Chart

Spec Sheet

Product Manual

Controller Manual

Warranty 

Energy Systems Central is an authorized dealer of BAS Energy Systems.

Warranty Document