The 5-Step Standby Generator Checklist (From Someone Who Messed Up Twice)

This checklist is for you if you're considering a standby generator—specifically something in the Generac 15,000e range—and you want to avoid the mistakes that cost time, money, and credibility. I've personally made two significant errors on generator projects (totaling roughly $3,200 in rework and delays). This list exists because of those failures.

There are 5 steps here. Follow them in order, and you'll save yourself a lot of headaches.

Step 1: Size Correctly (But Don't Trust the Calculator Blindly)

The single biggest mistake I see people make is trusting the online load calculator without validating it against real-world usage. I did this in 2023—plugged in numbers for a 5,000 sq ft home with a well pump, AC, and some appliances. The calculator said 22kW. My gut said something felt off. Turns out, the calculator assumed a starting load of 150A for the AC, but the actual unit drew closer to 80A under normal conditions. I ended up with a unit that was 40% oversized. Not cheap.

What to do instead:

• Get a professional load study from your electrician. Not from the generator manufacturer's website.
• Ask your utility for a demand profile. They can give you a 12-month history of peak usage.
• Account for non-linear loads (e.g., variable-speed well pumps, modern refrigerators with inverter compressors). These don't follow simple starting-load formulas.

For most homes, Generac's 15,000e (or 15kW class) is actually a sweet spot—not too big, not too small. But if you have a 4-ton AC and a 1.5 HP well pump running simultaneously, you might need to bump up to 18kW. (Don't hold me to this—circa 2024, load profiles differ wildly by region.)

Step 2: Check Fuel Supply—This Is Where Most People Get Stuck

This is the step I ignored on my second project, and it cost me a 3-day delay and a $890 bill for a gas line upgrade. Here's the thing: Generac's dual-fuel models (natural gas/liquid propane) are great in theory. In practice, the natural gas supply needs to meet a specific CFH (cubic feet per hour) rating. If your meter won't handle it, you'll either drop pressure or stall the unit.

How to verify:

1. Find your gas meter's capacity rating (usually stamped on the meter housing).
2. Calculate the generator's demand at full load. For a 15kW unit running on natural gas, that's roughly 150-200 CFH depending on efficiency.
3. Subtract the existing load of your furnace, water heater, range, etc. If the remaining capacity is less than what the generator needs, you need a meter upgrade or a larger propane tank.

I'd argue that 80% of generator service calls I've seen in Redford, MI (where I handle service orders) are related to fuel starvation—not generator failure. It's the most commonly ignored factor.

Step 3: Install the Transfer Switch Correctly (Seriously, Don't Skip the Manual)

I'm not going to sugarcoat this: I've seen three installations where the electrician wired the transfer switch to the wrong breakers. The result: the well pump ran when the power was off, but the refrigerator didn't. Not ideal.

The checklist item:

• Map out your critical loads. List every circuit you want backed up and assign a priority (1-5 scale). The transfer switch should only handle circuits above a '3' priority.
• Use the included wiring diagram (I know, boring). Generac provides a specific diagram for each model. I learned this the hard way after a $450 rewire in April 2024.
• Test the transfer sequence before the concrete sets under the generator pad. It's easier to fix a wiring error when the unit is still on the trailer.

To be fair, some electricians will tell you that any 200A service panel can handle a 50A transfer switch. That's true—but only if the breakers are properly labeled. Don't let the contractor skip the labeling step. (Granted, this adds 30 minutes to the job. Worth every minute.)

Step 4: Verify the Site—Concrete Pad, Drainage, and Clearances

In my first year (2017), I accepted a quote for a generator installation without checking the site. The result: the pad was poured too close to the house (less than 18 inches from the wall), which violated the manufacturer's clearance requirements and local fire codes. I had the pad saw-cut and the unit relocated. Total cost: $1,200. Lesson: check clearances before you pour.

What you need to verify:

• Clearance: Minimum 18 inches from the house (for air circulation). 3 feet from windows or vents. Check local codes—some municipalities require more (e.g., 5 feet in certain jurisdictions).
• Drainage: The pad should be 4-6 inches above grade, sloped away from the house for water runoff. I've seen foundations crack because water pooled under the pad.
• Ventilation: If the generator is installed in an enclosure, make sure there's airflow on three sides. Generac's specs call for 24 inches of free space on the exhaust side.

I'm not 100% sure why some dealers skip this step. My best guess is that they assume every site is identical—which is never the case.

Step 5: Test the System (Under Load, Not Just Idle)

I can't tell you how many times I've seen a generator tested at no load for 10 minutes, declared 'good,' and then fail to start when the power actually went out. Testing under load is non-negotiable.

The procedure:

1. Simulate a power outage (shut off the main breaker).
2. Start the generator (manually, not via automatic transfer). Let it run for 5 minutes to stabilize.
3. Transfer the load manually (or let the ATS do it). The generator should handle 50% of its rated capacity for 30 minutes. If it trips or stalls, something is wrong.
4. Run a full-load test (100% rated capacity) for 1 hour. This is where most 'inverter' or 'portable' generators fail—they can't sustain peak load. But standby units like the Generac 15,000e should handle this.
5. Check for voltage drop, RPM stability, and sound levels. If the unit sounds like a lawn mower on steroids, you might have an exhaust leak.

I'd argue that every generator service in Redford, MI should include a load bank test before the technician leaves. Per FTC guidelines (ftc.gov), a service provider should be able to demonstrate that the system works—not just promise it.

Final Notes & Common Mistakes

One thing I've never fully understood: why some homeowners install a generator and never check the oil level until the first power outage. That's like buying a car and never checking the gas gauge until it runs dry. Generac recommends checking oil every 50 hours of runtime—but most people check it once a year (if that).

If you're in the 20% of cases where this checklist doesn't apply:

• If you have a three-phase connection (rare for residential), you need a three-phase generator.
• If your property is off-grid or has a solar system with battery backup, the generator needs to be compatible with the inverter setup.
• If you're in a flood zone, the generator needs to be elevated above base flood elevation.

Pricing note: Costs as of Q1 2025. The Generac 15,000e runs roughly $4,500-$6,000 for the generator alone (based on dealer quotes in the Midwest; verify current rates). Installation adds $2,500-$4,000 depending on site complexity.

This list has been updated as of January 2025. The market changes fast—verify your local codes and current pricing before committing to a purchase.