The 6-Step Generator Spec Checklist for Facility Managers (Briggs & Stratton Edition)

If you're like me—an office administrator or facility manager who suddenly gets handed the "find a backup generator" project—you probably don't have a degree in electrical engineering. I've been managing purchasing for a 120-person company since 2020, and when my VP asked for a "storm-ready solution" after our third outage last year, I had to learn fast.

This checklist isn't about theoretical load analysis. It's the six-step process I now use to turn technical generator specs into practical purchasing documents.

Who this checklist is for

This is for anyone who needs to specify a Briggs & Stratton generator for a commercial building—not an industrial plant, not a home. Think multi-tenant offices, small manufacturer facilities, or distribution centers. If you're navigating a budget from operations and a laundry list of requirements from your maintenance lead, you're in the right place.

These six steps go from broad (how much power do you actually need?) to dead specific (where's the air filter intake facing?).

Step 1: Start with the load calculation — but don't overcomplicate it

The first thing I learned is that "load calculation" sounds scarier than it is. You don't need a power audit from a consultant. What you need is a list of essential circuits.

Here's what we did: I walked through our main office with the building engineer and flagged everything that must stay on during an outage. For us, that was the server room (critical), the front office lighting, a single HVAC unit for the server room, the security system, and one elevator in a two-story building. We didn't include kitchen appliances or the entire HVAC system.

Total essential load: around 18kW running, with a surge around 28kW when the elevator started.

Checkpoint: Your list should be 60-70% of your total building load at most. I don't have hard data on industry averages, but based on four vendor consultations, over-speccing by 20% is the norm for commercial. You're buying insurance, not a daily driver.

This pointed us directly at the 12kW briggs and stratton generator class—though we actually sized up a bit. More on that later.

Step 2: Match the type to your environment

It's tempting to think you just need "the biggest generator in the price range." But choosing between portable, standby, and whole house isn't just preference—it determines installation cost, fuel logistics, and code compliance.

For commercial use, you've got two realistic options:

• Standby / whole house generators — permanently installed, automatic transfer switch included, runs on natural gas or propane. Ideal for buildings where you can't have someone physically there to flip switches.
• Portable generators with a transfer switch — cheaper upfront, but require manual setup, refueling, and storage. Better for facilities where someone is on-site during outages.

The 'always get the cheapest portable' advice ignores the labor cost of staging and fueling a portable unit during a storm. Our facility manager's time alone was worth the difference.

We went with a Briggs & Stratton standby generator connected to our natural gas line. The 12kw briggs and stratton generator was in our price range and covered our essential load with some room.

Side note: If you're considering portable, the briggs and stratton 5550 watts 8550 starting watts generator is a solid unit for light commercial backup of a single critical load—think a server closet or a small workshop—but it won't power an entire office.

Step 3: Power requirements — understand running vs. starting watts

This is where the marketing gets confusing. A generator's spec sheet lists both running (continuous) watts and starting (surge) watts. Motors (elevators, large HVAC units) draw 2-3x their running load on startup.

My mistake the first time? I looked only at running watts. The 12kw unit seemed plenty for our 18kW load. But when I factored in start-up surge for that elevator and the server room AC unit, we needed something with a 30kW+ surge capacity. We ended up with a 20kW standby unit.

Rough rule of thumb: Your generator's surge rating should be at least 1.5x your total starting load. Check the spec sheet for "surge capacity" or "starting watts." The briggs and stratton 5550 watts 8550 starting watts generator has a 3,000-watt gap between its running and starting specs—that's typical for motors.

I wish I had tracked our calculation more carefully from the start. What I can say anecdotally is that upsizing by 3-5kW from your initial calculation is fairly standard practice.

Step 4: Fuel — dual fuel isn't always the answer

Briggs & Stratton offers dual fuel models (gasoline and propane), and they are tempting. But for commercial standby, fuel logistics are a real consideration.

Natural gas generators run indefinitely as long as the gas supply is intact—no refueling, no storage permits. Propane requires a tank (often a 500-gallon underground tank for commercial use). Gasoline requires proper storage and rotation every 6-12 months.

If your building has natural gas, a dedicated gas standby unit is usually the most reliable option. Dual fuel makes sense for mobile applications or facilities where natural gas isn't available.

I'll be straight with you: I'm not an expert on local fire codes for fuel storage. That's a conversation you need to have with your facility team and local authorities. But I can tell you that our local fire marshal flagged our original plan for a 55-gallon gasoline drum—that's a commercial storage hazard.

Step 5: Think about fuel logistics and the transfer switch

This brings up a component I hadn't considered initially: the ups transfer switch. (Or more commonly for generators, an automatic transfer switch or ATS.)

The transfer switch isolates the generator from the grid, preventing backfeeding and protecting utility workers. For a 12kw briggs and stratton generator or larger, you'll need a proper ATS rated for that capacity.

Three things to check:

• Capacity: The ATS must match or exceed the generator's output. A 12kW generator needs a 60-amp ATS minimum.
• Location: Indoors or weather-protected enclosure. Some installs require a separate enclosure.
• Compatibility: Most modern Briggs & Stratton units come with a matching transfer switch kit. Don't mix brands unless you verify compatibility.

Knew I should verify the transfer switch specs before we placed the order, but figured 'they're all basically the same.' Well, the one time it mattered was when our vendor quoted a 50-amp ATS for a 12kW generator—undersized. Caught it in review, but definitely delayed the install by a week.

If your building uses a power on board smart battery charger or similar system for starting the generator engine, make sure the transfer switch includes battery charging maintainer support. Standby generators need their starting batteries topped off.

Step 6: Don't skip the 'minor' details — check the transfer switch compatibility

Here's something I bet 80% of first-time buyers don't think about: which way does an air filter go in on your generator? It sounds trivial until you're in a rainstorm trying to start a unit and you realize the filter orientation is causing a seal issue.

Specifically for Briggs & Stratton generators, many models use a cylindrical foam or pleated air filter. The orientation matters because if it's reversed, the pre-filter screen won't seat properly, letting debris into the intake.

Mark the airflow direction on the housing with a permanent marker when you install. We do this on every unit now after our facility manager spent 40 minutes figuring it out during a drill. (The right answer: on most B&S engines, the filter's open side should face the carburetor—the airflow arrow on the housing is the reference.)

Other small things that matter:

• Exercise cycle: Standby generators should run for 15-20 minutes weekly (usually automatic). If yours isn't self-exercising, you need a schedule.
• Battery charger: Some standby units include a power on board smart battery charger that maintains the starting battery. Worth having—dead batteries are the #1 failure point I've seen.
• Spark plugs and oil: First 5 hours of runtime = first oil change. Standard maintenance intervals after that: every 100 hours or annually. Use a ups transfer switch-compatible oil.

Common mistakes I've seen (and made)

1. Sizing for 'just-in-case' full building power. A generator that covers 100% of your load is 2x to 3x more expensive than one covering essential loads. Decide what's truly critical.
2. Forgetting about fuel storage. Gasoline degrades in 6 months. Propane tanks need permits. Natural gas ties you to the grid—defeats the purpose if the gas line goes down.
3. Skipping the 'which way does an air filter go in' check. It sounds silly, but it's a real source of startup failures.
4. Not planning for installation setbacks. Most standby generators need a concrete pad and a minimum 1.5-foot clearance from windows and doors. Check local setbacks.

The goal with this generator checklist is to save you the $2,400 mistake I made with the wrong ATS and the time wasted on filter orientation. An informed buyer asks better questions and ends up with a system that actually works when the power goes out.

Pricing note: Generator prices vary significantly by region, installer, and time of order. Based on online quotes January 2025, a 12kw briggs and stratton generator with ATS runs roughly $2,500–$3,800 for the unit alone. Installation adds $1,500–$3,000 depending on fuel line routing and concrete pad. Always verify current rates with an authorized dealer.