Generac Generator FAQ: 8 Questions You Should Ask Before Buying or Maintaining One

What You’ll Find Here

I’m a quality compliance manager at an electrical equipment distributor. Every year I review roughly 200+ generator units before they reach our customers—checking specs, build consistency, and whether the documentation matches reality. In Q1 2024 alone I rejected 12% of first deliveries due to mismatched wiring diagrams or loose fasteners.

Below I answer the most common questions I hear from buyers—whether you’re looking at a Generac generator clearance deal or trying to figure out why your portable generator won’t start. No fluff. No sales pitch.

1. What does “Generac Generator Clearance” actually mean?

It’s tempting to think clearance means “defective”—or the opposite, “amazing deal with zero risk.” Neither is quite right. In my experience, clearance stock usually falls into one of three buckets: discontinued models (manufacturer wants shelf space), overstock from a dealer who ordered too many 22kW units before hurricane season, or floor models with cosmetic scuffs. I’ve seen all three. The 2024 clearance batch we handled had units with dented panels but fully functional internals—saved buyers about 25% versus list. What most people don’t realize: clearance units often come with the same full warranty, but you should verify that before paying. Ask the dealer for the serial number and run it against Generac’s warranty lookup tool. (Should mention: some clearance deals exclude the transfer switch—that’s an extra $400–$700 you’ll need to budget.)

2. Is the Generac 5939 GP Series Portable Generator any good for home backup?

The 5939 GP Series (5500W running / 6875W peak) is what I’d call a “weekender” generator—great for powering your fridge, a few lights, and a sump pump during a 6-hour outage. It won’t run your central AC or a 240V well pump. Where I see people get into trouble: they assume “portable” means “take it anywhere,” but the 5939 weighs 120 lb dry. It’s not something you haul to a job site daily unless you’ve got a truck and a ramp. The engine is Generac’s own 196cc OHV—reliable, but the carburetor can be finicky if you let stale gas sit for months. I still kick myself for not draining the fuel on my test unit after a demo; the next spring it needed a $65 carb cleaning. So glad I caught it on my own unit rather than a customer’s.

3. What electrical plug do I need for a Generac portable generator?

This is where I see the most confusion—and the most dangerous setups. Most Generac portable generators (including the 5939) come with a 5-20R 120V duplex outlet (standard household plug) and a L14-30R 120/240V twist-lock outlet. The twist-lock is what you’d use with a transfer switch. I’ve rejected plenty of DIY installations where someone used a “suicide cord” (double-male adapter) to backfeed their panel. That kills linemen. It’s also against code and can burn your house down. Buy a generator inlet box + interlock kit—total cost about $150–$250 if you DIY. I’d argue that’s non-negotiable.

4. Can I buy a Generac generator at Lowe’s? What’s the catch?

Yes, Lowe’s carries Generac portable generators (the GP series, and some standby models online). The catch is service. Lowe’s isn’t a Generac-authorized service center—if your unit has a warranty issue, you’ll be referred to a local dealer for repairs. That’s fine for a $600 portable, but for a 22kW standby that costs $4,000+, I’d rather buy from a dealer who does their own installations and service. I’ve seen cases where a Lowe’s unit sat in the box for a year, then the buyer tried to register the warranty and discovered the serial number had already been activated (store demo unit). The good news: Generac’s warranty is transferable if you have the original receipt. Without it? You’re relying on the store’s return policy.

5. Clean vs dirty air filter: does it really matter for a generator?

Short answer: yes, and it’s one of the most overlooked maintenance items. A dirty air filter restricts airflow, which richens the fuel mixture. The engine runs hotter, misfires under load, and can clog the spark arrestor. I ran a quick test last year: a Generac GP5500 with a clean filter pulled 5300W before voltage dropped below 115V. With a dirty filter (one season of use on a construction site), it sagged at 4400W. That’s a 17% loss. The fix takes 5 minutes and costs $8–$15. Clean is better—period. Dirty isn’t “still okay” until it’s obviously caked. Check it every 20 operating hours or before you store it.

6. Are Generac generators compatible with natural gas and propane?

Most of the standby generators (like the 22kW or 26kW) are available with a dual-fuel carburetor from the factory. You don’t need an aftermarket kit. Portable models? The GP series is gasoline-only—no conversion available that I trust. I’ve seen customers try $50 conversion kits from Amazon and end up with flames shooting out the exhaust. If you need dual-fuel in a portable, look at Generac’s XD series (like the XD5000E) or consider a different brand. For standbys, the choice between natural gas and propane depends on your local fuel availability and BTUs per cubic foot. Propane produces slightly less power (roughly 5–8% less), but it stores indefinitely—which matters if you live in an area with freeze risks.

7. Should I install my Generac generator myself to save money?

I get why people think this—installation quotes from dealers can run $1,500–$3,000. But I’ve rejected three DIY installations this year alone where the transfer switch was wired backward, the generator sat too close to the house (violating 5-ft clearance), or the gas line had the wrong regulator. One of those was a $22,000 mistake—the homeowner burned up his panel and Generac wouldn’t honor the warranty because the installation wasn’t done by a licensed electrician. To be fair, some people are capable of doing it safely. But the risk isn’t the installation itself—it’s the liability. If your DIY install causes a fire, your homeowner’s insurance may not pay out. I’d argue it’s worth paying a pro, at least for the transfer switch and gas hookup.

8. What’s the single most important thing most buyers overlook?

Annual maintenance costs. People budget for the generator but forget the tune-up: oil change, air filter, spark plug, and battery check (for standbys). For a 22kW unit, plan on $150–$300 per year if you do it yourself, or $300–$500 if a dealer does it. I assumed my first standby would be “set and forget.” Turned out the battery died after two years because I didn’t run the weekly exercise cycle. The no-start happened during a real outage. That was a lesson I learned the hard way. If you buy a generator, set a calendar reminder every 6 months to check the battery voltage and run it under load for at least 30 minutes. Small habit. Big difference.