Introduction: The Questions I Actually Get Asked
Over four years of reviewing generator specs and installations—roughly 200+ units annually for our 50,000-unit order pipeline—I've heard the same questions repeat. Some are smart. Some miss the point entirely. This FAQ is the ones I'd answer if you cornered me at a trade show. No fluff. Just what matters when you're specifying, buying, or installing a Generac generator.
What is an inverter generator, and why does Generac make them?
An inverter generator produces cleaner power by converting AC to DC and back to AC, regulating voltage more tightly than conventional alternator-type generators. The result? Less than 5% total harmonic distortion (THD)—clean enough for sensitive electronics like laptops, smart home hubs, and variable-speed HVAC controls.
Generac's inverter models (like the GP series) are designed for portable use where power quality matters. The trade-off is cost and complexity. A conventional generator is simpler and often cheaper per watt. But if you're powering a home office or medical equipment, the inverter is worth the premium.
Here's the catch most buyers miss: inverter generators are quieter, but not all are home standby rated. Some portable inverter units can't handle continuous load for days. Always check the duty cycle rating.
How do I size a Generac standby generator for my home?
Stop guessing based on square footage. I've seen a 2,500 sq ft house need a 24kW unit (all-electric with well pump and AC) and a 4,000 sq ft house run fine on a 14kW (gas heat, no AC).
The real method: calculate your starting and running watts for essential loads.
- Starting watts: Motors (well pumps, AC compressors, refrigerators) need 2-3x their running watts to start.
- Running watts: All continuous loads combined.
Generac's sizing tool (available on their site) is decent, but I always overshoot by 20%. Why? Because in 2022, a client spec'd a 22kW unit based on his current load, then added a 240V EV charger the next month. The upgrade cost us $4,800. Size for tomorrow, not today.
What's the difference between the Generac 8kW portable generator and a standby unit?
Short answer: the 8kW portable is manual operation. You wheel it out, plug it in (via transfer switch or extension cords), start it, fuel it, and shut it down yourself. It's not weatherproof (though covers help) and doesn't have automatic transfer switching.
A standby generator, by contrast, integrates with your home's electrical panel, fires up automatically when power drops, and runs until utility power returns. The 8kW portable is great for job sites or RV use. For whole-home backup, look at the 14kW or 22kW standby models.
One nuance: the 8kW portable can technically power a fridge, a few lights, and a 1/2 HP well pump. But if you try to run a 5-ton AC unit on it, you'll trip the breaker. Know your loads.
Can I use a Skil 12V battery charger with my Generac generator?
Yes, but with a caveat. Generac generators (especially older models) produce power with some voltage fluctuation, particularly when the engine RPM sags under load. Modern smart battery chargers, including the Skil 12V, are generally tolerant of this—they have built-in protections.
But if you're charging lithium-ion batteries (LiFePO4 or standard Li-Ion), some chargers are picky about voltage. I've seen a $200 battery charger fail because the generator's voltage dipped to 108V during a compressor start. Use a generator with inverter technology or a voltage regulator.
What about the Ford 6.7 high-pressure fuel pump? Is that related to generator use?
Not directly, but I get this question because generator owners often have diesel trucks to haul them. The 6.7L Power Stroke's CP4 high-pressure fuel pump has been a known failure risk (2011-2019 models) that can send metal shrapnel through the fuel system—$8,000+ repair. If you're running a generator off your truck's fuel tank, or storing diesel for both, fuel contamination is a real crossover risk.
My advice: If you have a 6.7L Ford with the CP4 pump, install a Diesel Fuel Contamination Kit (like S&S or Exergy) before using that truck to fuel a generator. It's $400 and saves a lot of headaches.
What's the Warranty on Generac Generators, and What's Not Covered?
As of January 2025, Generac's standard residential standby warranty is:
- 5 years on the alternator and engine (parts and labor for first 2 years)
- 2 years on the controller and transfer switch
- 1 year on the battery
But here's what most people miss: the warranty excludes damage from improper installation, fuel contamination, and lack of maintenance. I've rejected warranty claims because the owner didn't change oil after the first 25 hours (it's in the manual). Another guy voided his warranty by using old gasoline that gummed up the carburetor.
Keep a logbook. Actually do the maintenance. It's cheap insurance.
How Loud is a Generac Generator? Is It Legal?
Standby generators (like the 22kW) operate at about 66-70 dB at 23 feet—roughly the noise level of a vacuum cleaner or normal conversation. Portable generators are louder: 70-85 dB depending on load. Inverter models are quietest (48-60 dB).
Local noise ordinances vary wildly. In my experience, zoning laws in California cap residential generator noise at 60 dB at the property line—which rules out most portable units. Check your local code, and install a sound-attenuating enclosure if needed. Generac offers optional sound blankets for some models.
I've only worked with North American installations and residential-to-light-commercial applications. If you're spec'ing industrial or international applications, your experience might differ significantly.
