I've Bought Perkins Generators for 3 Facilities. Here's My 7-Step Checklist

Who This Checklist Is For

If you manage facility procurement and you've been handed the job of sourcing a backup generator—or keeping one running without overpaying on parts—this checklist is for you. I'm not an engineer. I'm an office administrator who runs purchasing for three sites and about $1.2M a year in vendor spend. Somewhere along the way, generators, transfer switches, and fuel-system parts ended up in my queue.

I've put together seven steps. They're not in perfect order of importance. They're in the order I actually go through them. If you follow them loosely, you'll avoid most of the mistakes I made in my first two years.

It took me three facilities and about four years to understand that buying a generator is mostly a paperwork exercise with a machine at the end of it. The paperwork is where projects fall apart.

Step 1: Size the load before you size the generator

The first mistake I made—this was in 2021, on our second facility—was letting the specs lead the conversation. The vendor quoted a 120 kW standby unit, and I approved it because 120 kW sounded like a lot of power. It was. It just wasn't the right amount.

Before you accept any quote, ask your operations lead or electrical contractor for a written load list: lighting, HVAC, critical IT, refrigeration, motor startup current. Add it up. Apply margin for future expansion. Only then should you look at power ratings.

If that sounds basic, it is. But I've watched two peers at other companies skip this step because their vendor "already knew" what they needed. The vendor knows what they sell. They don't know your building.

Step 2: Match the power rating to the duty, not the brochure

Standby and emergency are not the same label, even when the generator is.

A 450 kW Perkins emergency generator is typically built for code-driven life-safety loads—egress lighting, fire pumps, elevators, essential circuits. A 120 kW Perkins standby generator is more often sized for business continuity—keeping the server room, POS systems, and a few key zones alive during an outage.

I went back and forth between a 120 kW standby spec and a 450 kW emergency spec on our flagship site for about two weeks. The 450 offered headroom and code compliance. The 120 was roughly $40K less installed. I finally pulled the trigger on the larger unit because our insurer asked a specific question about life-safety coverage that I couldn't answer with the smaller one. That question alone ended the debate.

Ask your insurer and your local AHJ (authority having jurisdiction) what they require. Not what you can get away with.

Step 3: Demand a written fuel system spec

Most generator quotes stop at the engine. Fuel delivery is where I've seen the most invoice disputes.

Ask for, in writing:

• Tank capacity and location
• Day tank vs. main tank arrangement
• Fuel pump type and voltage
• Filter and water separator model numbers
• Whether the fuel system meets NFPA 110 requirements for your occupancy class

On our smaller site, the tanks sit below grade. The OEM fuel lift pump couldn't pull from that height reliably, so the supplier recommended a low-pressure auxiliary pump. In our case, that meant specifying a 6 volt fuel pump rated for diesel, with a check valve and secondary filter. I had to confirm the voltage matched the control panel circuit—something I wouldn't have thought to ask about two years ago.

If a supplier can't hand you a one-page fuel spec, that's a warning. Not fatal, but a warning.

Step 4: Learn one basic mechanical fuel pump test

I realize this is a facility procurement article, not a shop manual. But if you're responsible for anything with a diesel engine on site, this test is worth memorizing. It saved us a service call last winter.

How to test a mechanical fuel pump, roughly:

1. Disconnect the outlet line (the one going toward the engine) and route it into a clear container.
2. Crank the engine for about 10 seconds, or use the manual priming lever if your pump has one.
3. Watch for a strong, steady pulse of fuel. Weak spurts or nothing usually means a bad diaphragm, a clogged inlet, or a stuck valve.
4. Reconnect everything, tighten fittings, and check for leaks before you start the engine for real.

That's the whole test. I'm not a mechanic, but I know what a healthy pulse looks like now. So does the maintenance lead at site two. When the pump on our 120 kW standby unit started acting up in December 2024, we caught it before it turned into a no-start event.

If your team can't do this, get a service contract that includes it. Don't assume the annual inspection covers it—ask.

Step 5: Don't forget the small-engine fuel filters

Here's the step most people skip. Facility generators get all the attention. The grounds crew's equipment gets none.

When I took over purchasing, our landscapers were buying weed eater fuel filter parts individually from a hardware store—twelve dollars each, no invoice trail, no asset tracking. I consolidated that into a standing quarterly order with our industrial supplier. Different part, same SKU discipline as the generator filters.

A weed eater fuel filter is a small thing—literally. But a clogged filter on a trimmer in July is a half-day of landscaping work lost. And if the crew is buying them off the books, you can't audit the spend. I learned that one the hard way in 2022 when a landscaping invoice came in $800 higher than expected and I couldn't reconstruct why.

Step 6: Verify invoicing and documentation before placing any order

This is the step I now do first, no matter what the equipment is.

In 2021, I approved a purchase order with a new supplier who quoted well below our regular vendor. The equipment arrived on time. The invoice was handwritten. Finance rejected the expense report outright, and the cost landed on my department's budget. I don't remember the exact figure—I want to say $1,400, but honestly it might have been closer to $1,900; I'm mixing it up with a different incident that same quarter. The point isn't the number. The point is that I didn't check whether the vendor could produce a proper invoice until after the money moved.

Before you sign anything, confirm:

• Can they issue a standard invoice with tax ID and PO reference?
• Do they provide datasheets for every part number (Perkins OEM numbers included)?
• Is there a written warranty path?
• Will they send an order acknowledgment before shipping?

None of this is exciting. All of it is what keeps the purchase clean on the back end.

Step 7: Lock in a consumables schedule

Generators don't fail because the engine is bad. They fail because the oil filter wasn't changed, the fuel filter sat too long, or the coolant was never checked.

Set a schedule before the unit arrives—not after the first service call. At minimum:

• Oil and oil filter: per manufacturer interval or annually, whichever comes first
• Fuel filter and water separator: annually, or per fuel quality
• Air filter: annually, or after dusty-season operation
• Load bank test: annually (this is the one most facilities skip)

Put the schedule on your calendar with a named owner. In our case, that's me for the purchase order, and the site maintenance lead for the actual work. Two people, one schedule, no confusion.

Common Mistakes to Avoid

A few things I've seen—some from my own files:

Buying by price per kW. The lowest per-kW number often excludes switchgear, fuel system, installation, and commissioning. When I compared our Q1 2023 quotes side by side, the "cheapest" option was actually $22K higher once those line items were added back.

Treating standby and emergency as interchangeable. Codes differ. Insurers care. Don't let a salesperson tell you they're the same thing.

Skipping the small-engine parts. A weed eater fuel filter or a 6 volt fuel pump is a small line item until it isn't. Standardize the part numbers and put them on the same purchase order as the big-kid filters.

Assuming the service contract covers "everything." It doesn't. Read the exclusions. Then ask what it costs to add them.

That's the list. None of it requires an engineering degree. It just requires asking the boring questions in the boring order, and not letting a bottom-line number talk you out of the paperwork.