If you're looking at a Generac generator, you're probably searching for the same things I was: reliability, peace of mind, and not getting taken for a ride on the extras. After managing purchasing for our office and handling my own home install, let me save you some time and money.
The most expensive part of a generator isn't the unit itself—it's the mistakes you make buying and setting it up. I learned this the hard way, and I'm going to walk you through the specific ones that cost me.
Mistake #1: Not Checking the Battery Compatibility for Your 7500 Watt Unit (Or, The Day My Power Was On, But My Generator Wasn't)
I thought a generator battery was a battery. You grab a standard one, hook it up, and go. Wrong.
Two years ago, I ordered a battery for my Generac 7500 watt generator based on the cheapest option from a parts website. It was the wrong size physically—didn't fit the tray. Then the wrong terminal type. By the time I found the correct one, a storm had already come through and we were out of power for 16 hours with a dead backup system. (Note to self: verify part numbers before clicking 'buy'.)
Most buyers focus on the engine size or the wattage, but completely miss the battery spec. For the 7500-watt models, the OEM battery is typically a Group U1R. Don't rely on a generic 'fits all' listing. Cross-reference the Generac part number (0G0889A or similar) with your model. The price difference between the right battery and the wrong one? About $40. The cost of a night without power? Priceless.
Mistake #2: Skipping the Generator Wheels Kit (My Back Still Remembers)
Here's a fact: a 20kW home generator weighs roughly 400-500 pounds. You are not going to move it by yourself. The generator generator wheels kit isn't an accessory—it's a necessity.
The frustrating part? The wheels come separately. You'd think a complete unit would include them, but Generac sells them as an add-on (kit 0E7720A, roughly $80-120). After the first time we tried to wheel the unit into place on a dolly (across fresh gravel, ugh), I ordered the official kit immediately. Dodged a bullet when a co-worker suggested a universal dolly instead—it would have scraped the bottom panel. The Generac-specific wheels bolt directly into the frame.
If you're installing on a concrete pad, you might get away with a furniture dolly. But for any other surface, just buy the kit. It's one of the few times the 'official' part is actually the cheapest solution in the long run.
Mistake #3: Ignoring the Air Filter (And Why I Now Buy a 2-Inlet Filter)
I'm not a mechanic, so I can't speak to engine internals. What I can tell you from a procurement perspective is that maintenance items are the easiest thing to forget until they fail.
Our office generator had a standard air filter. After a particularly dusty construction project nearby, it clogged in 3 months. The unit started to run rough, threw a code, and shut down. The service call alone cost more than a 2 inlet air filter upgrade would have cost.
The '2 inlet' design isn't standard for every model, but it's a massive upgrade for any unit operating in a semi-dusty environment. It doubles the surface area and reduces the restriction on the engine. It's not just about lasting longer—it's about the engine running at peak efficiency when you need it most. Check if Generac offers a retrofit filter kit for your model (like the 0F3700 for some Guardian series). It's a $30 part that can save you a $300 repair.
Mistake #4: Assuming a 20kW Home Generator is 'Plug and Play'
The question everyone asks is, 'How much does a 20kw home generator cost?' The question they should ask is, 'What else do I need to budget for?'
A 20kW unit (like the Generac 7223 or 7224) is a beast. It can power an entire mid-sized home. But the unit price ($2,500-$3,500) is only 40-50% of the total installed cost. You also need:
- A concrete pad ($300-600)
- Electrical wiring and a transfer switch ($800-1,500)
- Gas line installation ($400-1,200 for natural gas, more for propane)
- Permits and inspection ($150-400 depending on your locality)
I nearly made the mistake of buying the unit first and figuring out the rest later. A local electrician friend stopped me. 'You'll have a very expensive lawn ornament in your backyard,' he said. I priced the entire project with the installer first. That's the order.
Mistake #5: The 'How to Connect Generator to House Without Transfer Switch' Rabbit Hole
This is the most dangerous search on the internet. I've seen forums where people suggest backfeeding through a dryer outlet. Simple advice: don't. It's against the National Electrical Code (NEC) and it can kill a lineman working to restore power.
For a portable unit, you have two safe options: a manual transfer switch ($400-800 installed) or an interlock kit ($100-200). For a standby unit like the Generac, an automatic transfer switch is mandatory and comes as part of a bundle. The 'backfeeding' shortcut comes from an era when codes were less strict, or from people who got lucky. It's a loaded gun. Spend the money on a proper transfer switch.
Final Thought: The Best Advice I Got
The most valuable piece of advice I received came from our installer: 'Size the generator for future plans, not just the current load.' We were planning to add a heat pump in a few years. A 20kW unit gave us that headroom. A 16kW unit would have been maxed out.
So glad I listened. Almost went for the smaller unit to save $800 upfront, which would have meant another full install in three years.
An informed customer is the best customer. You're already doing the research—don't skip the boring bits like the battery, wheels, and air filter. That's where the real savings (and headaches) hide.
