Briggs & Stratton Fortress 35kW Commercial Standby Generator, 120/240V Single-Phase

Is the Briggs & Stratton Fortress 35kW the Right Standby Generator for Your Business?

The Briggs & Stratton Fortress 35kW (model 076830) is a liquid-cooled commercial standby generator for 120/240V single-phase service. It's rated 35kW on either liquid propane or natural gas (145 amps), runs on a 4,300cc engine and starts automatically when utility power fails. Briggs & Stratton assembles and engineers it in the USA with domestic and foreign parts.

The 35kW is built for small businesses that need commercial-grade backup on single-phase service: restaurants, retail, offices, clinics, shops and farm operations that want the whole building covered, not a few circuits.

Mighty Generators supplies the Fortress 35kW by quote. It ships freight direct from the manufacturer, typically in 5 to 6 weeks, so you can have the pad, gas line and transfer switch ready when it arrives.

Fortress 35kW at a Glance

• Standby rating: 35kW LP / 35kW NG
• Electrical: 120/240V single-phase, 145 A LP / 145 A NG, 150 A circuit breaker
• Engine: 4,300cc, liquid cooled
• Fuel: liquid propane or natural gas
• Normal operating sound: 68 dB (Briggs & Stratton rating)
• Size and weight: 91 x 39.4 x 41 in (L x W x H), 1,541 lb
• Enclosure: aluminum, powder coated, with a block heater as standard
• Rated to UL 2200 and CSA C22.2 No.100-14

Briggs & Stratton Fortress 35kW Features and Performance

Engine and Fuel

The 4,300cc liquid-cooled engine runs on liquid propane or natural gas. Briggs rates the same 35kW and 145 amps on either fuel. At 50% load it uses about 262,000 BTU per hour on propane or 258,000 BTU per hour on natural gas. A block heater is standard, so the engine is warm and ready to take load in cold weather.

Monitoring and Control

The Briggs & Stratton controller manages automatic start and transfer. EnergyTrak remote monitoring adds an app that shows generator status from anywhere and lets your dealer troubleshoot and diagnose issues remotely (subscription required).

Enclosure

The Fortress 35kW sits in an aluminum enclosure with an advanced powder-coat finish that Briggs designs to resist chips, abrasion and corrosion. Briggs lists its normal operating sound at 68 dB.

Where the Fortress 35kW Fits

Start with the electrical service. The Fortress line is 120/240V single-phase. If your building is on three-phase service, the Cummins RS Quiet Connect generators are the better match. Within single-phase, size from a load calculation that includes motor starting and HVAC, not from square footage, and our team can help match the result to the right Fortress size.

Fortress 35kW vs the Rest of the Fortress Line

Planning the Fortress 35kW Installation

• Transfer switch: required and quoted separately, sized to your service entrance.
• Delivery and pad: 1,541 lb assembled, 91 x 39.4 x 41 inches, shipped by freight.
• Fuel supply: give your gas utility or propane supplier the 258,000 BTU/hr (NG) or 262,000 BTU/hr (LP) 50% load figure and ask them to confirm capacity at full load.
• Code and placement: install to local code and NFPA 37, keep exhaust away from windows, doors, vents and crawl spaces, and keep carbon monoxide detectors installed and maintained in the building.

Briggs & Stratton Fortress 35kW Specifications

Standard Equipment Listed by Briggs & Stratton

• Block heater
• Briggs & Stratton controller
• Aluminum enclosure

Confirm the final configuration and any accessories on your written quote.

Frequently Asked Questions About the Briggs & Stratton Fortress 35kW

What electrical service does the Briggs & Stratton Fortress 35kW need?

The Fortress 35kW (model 076830) is a 120/240V single-phase generator with a 150 A circuit breaker. It suits businesses, farms and large properties on single-phase service. If your building has three-phase service, look at the Cummins RS Quiet Connect line instead, which is built for 120/208V three-phase.

How much power does the Fortress 35kW make on natural gas versus propane?

Briggs & Stratton rates the Fortress 35kW at 35kW and 145 amps on both liquid propane and natural gas. At 50% load it burns about 262,000 BTU per hour on propane or 258,000 BTU per hour on natural gas, which your fuel supplier will use to size the supply.

How loud is the Briggs & Stratton Fortress 35kW?

Briggs & Stratton lists a normal operating sound level of 68 dB for the Fortress 35kW. It's housed in an aluminum enclosure with a powder-coat finish, and Briggs & Stratton describes the liquid-cooled Fortress as commercial-grade.

What warranty comes with the Briggs & Stratton Fortress 35kW?

Briggs & Stratton's limited warranty on the Fortress 35kW covers parts, labor and travel for its full length. Briggs' published sources currently disagree on the number of years for this model, so we'll confirm the exact term in writing on your quote.

What should I plan for before installing the Fortress 35kW?

Plan for a 1,541 lb unit measuring 91 x 39.4 x 41 inches, plus a transfer switch, which is quoted separately. Installation has to follow local code and NFPA 37, including keeping exhaust away from windows, doors and air intakes. It ships freight direct from the manufacturer with a typical 5 to 6 week lead time, so request a quote with your service size and load list.

Warranty and Support

Briggs & Stratton's limited warranty on the Fortress 35kW covers parts, labor and travel for its full length, and we'll confirm the term in writing on your quote. Warranty coverage and service come from Briggs & Stratton and its dealer network. Mighty Generators is an authorized Briggs & Stratton dealer: we'll check the size against your load, quote the transfer switch, and coordinate freight to your site.

Ready for a quote? Use Request a Quote on this page, or call (888) 775-9048 with your service size and a list of the loads you need to carry.