I spent twelve years as a licensed electrician, and a good chunk of that was installing and servicing home backup power. The units themselves are reliable. The buying decisions people make around them, less so.
Most folks call me after the sale, not before. By then the concrete pad is poured, the wrong unit is bolted to it, and the fixes cost more than doing it right the first time would have. So let me get ahead of that.
Below are the seven buying a standby generator mistakes I ran into over and over on real jobs. None of them are exotic. They’re the everyday traps that catch smart people who just haven’t done this before.
Key takeaways
- Size for what you actually run, not the biggest number on the brochure, oversizing wastes money and undersizing trips the unit.
- Fuel type and gas line capacity make or break the install; check both before you sign.
- Budget for the transfer switch, gas work, permits, and pad, the generator is often half the total.
- A cheap unit with no local service network is a bad deal at any price.
Mistake 1: Guessing at size instead of doing a load calculation
This is the one I saw most. Someone reads that a 22 kW unit “powers a whole house” and buys it, or panics and buys a 48 kW monster for a 1,800-square-foot ranch.
Neither is right for most homes. An oversized generator costs more up front, burns more fuel at idle, and can actually run poorly under light load. An undersized one nuisance-trips every time the AC and well pump kick on together.
The honest answer comes from a load calculation, adding up your real starting and running watts, especially the big motors. A 3-ton central AC can pull 12,000 to 15,000 watts just to start. If you want the numbers, my walkthrough on how to size a generator for your home lays it out step by step.
Before you shop, spend twenty minutes writing down every appliance you truly need during an outage and its wattage. That one list settles most sizing arguments on the spot.
Mistake 2: Ignoring fuel type and gas line capacity
Natural gas is the easy sell, no tank, no refills. But I’ve flipped the switch on plenty of installs where the existing gas line simply couldn’t feed the generator plus the furnace, water heater, and range all at once.
A 22 kW unit can want around 300 cubic feet of gas per hour at full load. If your meter and piping were sized for a modest house, the utility may need to upgrade the meter or the installer has to run a larger dedicated line. That’s real money nobody mentioned at the showroom.
Propane isn’t automatic either
Propane works great, but you’re now buying or leasing a tank, and a whole-house unit can drain a 500-gallon tank in a few days of continuous running. Ask how many hours you actually get before you commit to a fuel.
Mistake 3: Forgetting the transfer switch and the rest of the install
The generator is one line item. The automatic transfer switch, the gas work, the concrete pad, the wiring, the permit, and the labor are the other line items, and together they often equal or beat the price of the unit itself.
On a typical job, a homeowner who budgeted $5,000 for “a generator” was genuinely surprised the installed total landed north of $9,000. Nothing was padded. That’s just what a code-compliant install costs.
Never let anyone talk you into a manual “suicide cord” or a backfeed setup instead of a proper transfer switch. It can push power onto lines and kill a lineman working to restore your service. The CPSC generator safety guidance is blunt about this for good reason.
Mistake 4: Skipping the permit and inspection
I get the temptation. Permits cost money and slow things down. But an unpermitted gas-and-electric install can void your homeowner’s insurance, tank your home sale, and, worst case, leak or arc without anyone ever checking the work.
A permitted install gets a second set of eyes on the gas connection and the electrical tie-in. That inspection has caught genuinely dangerous mistakes on jobs I’ve been near. Pay the fee.
Mistake 5: Buying on price alone with no local service
A standby generator is an engine that sits outside for fifteen years and is expected to start on the coldest, ugliest night of the year. It needs oil changes, filters, and the occasional part.
If you buy an off-brand unit online to save $1,200 and no dealer within 90 miles will touch it, you’ve bought a very heavy lawn ornament the day it breaks. I’ve turned down repair calls simply because I couldn’t get parts.
- Confirm at least one certified servicing dealer is within reasonable driving distance.
- Ask what a routine annual service visit costs, usually $200 to $400.
- Check parts availability for common wear items before buying.
- Read the fine print on the warranty terms and who honors them.
Warranties vary more than people expect, and “5-year” can mean very different things. It’s worth understanding what standby generator warranties actually cover before you pick a brand.
Mistake 6: Underestimating noise and placement
These units are quieter than the old jobsite generators, but they aren’t silent. A whole-house unit runs somewhere around 60 to 70 decibels at a few feet, think loud dishwasher, and it exercises itself weekly whether you’re home or not.
Put it under a bedroom window or three feet from the neighbor’s patio and you’ll hear about it. Code sets minimum clearances from windows, doors, and lot lines anyway, so placement isn’t fully your choice. I dig into the real-world numbers in this piece on standby generator noise levels.
A quick placement gut-check
| Factor | What to check |
|---|---|
| Exhaust direction | Points away from windows, doors, and vents |
| Clearance | Meets manufacturer and local code distances |
| Neighbors | Not aimed at their outdoor living space |
| Access | Room for a tech to service all sides |
Mistake 7: Buying more generator than the situation calls for
Not everyone needs a whole-house standby unit. If your outages are short and rare, and you mainly want the fridge, some lights, and a way to charge phones, a portable rig or a smaller circuit-level system may serve you better for a fraction of the cost.
I’ve talked homeowners out of five-figure installs because a good portable and a few hundred dollars of interlock hardware covered their actual risk. If you’re not sure which camp you’re in, it’s worth honestly asking whether you really need a standby generatorand reading up on portable generators for home backup before you spend big. For the full picture, my complete guide to whole-house standby generators covers the ground in one place.
How to buy one without the regret
Do the boring parts first: write your load list, confirm your fuel and gas line can handle it, and get two itemized quotes that spell out the switch, gas, pad, and permit, not just the box. If a quote hides those, that’s your answer about the installer.
Then pick the brand your local dealer actually services, not the cheapest one that ships. For general storm-readiness beyond the generator, Ready.gov’s power outage page is a solid, no-nonsense reference.
Get those pieces right and the thing will start every winter for years and you’ll forget it’s there. Which, honestly, is the whole point.
