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Generac generator sizes and prices line up in a straight ladder: the residential range runs from a 7.5kW essential-circuits unit to a 26kW whole house model, and the installed price climbs from roughly $6,000 to $15,000 as you go up the rungs. This page lists every size in the lineup, what each one can actually power, and what it costs bought and installed, so you can find your rung before you talk to a dealer.
The sizing question comes first because it drives the price more than any feature or brand decision does. Skip a size and the generator sheds load during outages; buy two sizes too big and you have spent thousands on capacity your panel will never use.
Generac generator sizes and prices at a glance
| Size | Fuel output (LP / NG) | Equipment price | Typical installed price | Best fit |
|---|---|---|---|---|
| 7.5kW PowerPact | 7.5 / 6.0 kW | $3,000 - $4,500 | $6,000 - $8,000 | Essentials only, 8 circuits |
| 10kW | 10 / 9 kW | $5,000 - $6,500 | $7,000 - $10,000 | Small home, essentials plus |
| 14kW | 14 / 12 kW | $5,500 - $6,500 | $7,500 - $10,500 | 1,500-2,000 sq ft, no central AC |
| 18kW | 18 / 16 kW | $5,500 - $7,000 | $8,000 - $11,000 | 2,000-2,500 sq ft with AC |
| 20kW | 20 / 18 kW | $5,500 - $7,500 | $8,500 - $11,500 | 2,500 sq ft, AC plus most loads |
| 22kW | 22 / 19.5 kW | $6,000 - $8,000 | $9,000 - $12,000 | Most 2,500-3,000 sq ft homes |
| 24kW | 24 / 21 kW | $6,500 - $8,500 | $9,500 - $13,000 | 3,000+ sq ft, two AC zones |
| 26kW | 26 / 23 kW | $6,500 - $9,000 | $10,000 - $15,000 | Large homes, whole panel |
Read those as regional ranges, not quotes. Equipment pricing is fairly consistent nationally, but installation labor, permits, and gas line work are local costs that move the installed column by $2,000 or more between towns. The full cost mechanics, including what installation adds line by line, are broken out in our Generac generator cost guide.
What each Generac size actually runs
The kilowatt number on the badge is the ceiling, not the shopping list. What matters is which loads you want running at the same moment during an outage.
7.5kW to 10kW: the essentials class. These cover a refrigerator, furnace fan, sump pump, some lighting, a router, and a phone charger. The PowerPact pairs with an 8-circuit, 50-amp transfer switch, so the circuits are chosen at installation and nothing beyond them powers up. Homeowners with short, rare outages and modest needs stop here, and the money not spent buys a lot of groceries.
14kW to 18kW: the family workhorse class. This band runs an entire 1,500 to 2,500 sq ft house minus the central air conditioner, or most of the house including a smaller AC unit. Add a well pump, a garage door opener, and a work-from-home office and you are squarely in 18kW territory. The Guardian 18kW is the value pick inside this band because its enclosure and pad requirements match the smaller units while its fuel draw stays reasonable.
20kW to 22kW: the whole house class for most homes. The 22kW is the volume seller for a practical reason: it starts a 3-ton or 4-ton AC compressor and still carries the rest of a typical panel without load shedding. If your summers make air conditioning non-negotiable, this is the floor, not the target. For a concrete walkthrough of matching a generator to a specific house size, see what size generator for a 2800 sq ft house, which runs the wattage math step by step.
24kW to 26kW: the large-home class. Two AC zones, a pool pump, an EV charger on a limited circuit, or a 3,500+ sq ft house with electric water heating push you into this band. The Guardian 26kW review covers when the top of the air-cooled line earns its price and when it is just headroom you will never use. Past 26kW, Generac switches to liquid-cooled commercial-style units, which is a different budget conversation entirely.
How to figure out which size your house needs
There are two honest ways to size a generator, and dealers use both.
The first is the checklist method: add up the running watts of everything you want live during an outage, then add the starting surge of the biggest motor, usually the AC compressor, which draws roughly three times its running load for a second or two. That total, with a 20 percent cushion, is your kW class.
The second is the square-footage shortcut, which is faster but coarser: roughly 1kW per 500 sq ft of living space gets a house through an outage with air conditioning, with electric heat or an all-electric home needing noticeably more. Our generator size calculator automates the checklist version and takes fuel type into account, which matters because every Generac unit in the table above loses 10 to 15 percent of its output when running on natural gas instead of propane.
Whichever route you take, have the answer before the dealer visit. A quote written around a correctly sized unit and a quote written around whatever the dealer has on the truck can differ by $3,000 in either direction.
Why prices move: fuel, installation, and the switch
Three cost variables sit outside the kW badge.
Fuel supply comes first. A natural gas connection at the meter is the cheap path, often $500 to $1,500 in gas line work. A buried propane tank adds $1,500 to $3,000 or more, plus refill logistics, though propane holds the unit's full rated output. The larger Guardian sizes are also thirstier than their smaller siblings on the same fuel line, so a 26kW on an undersized gas meter can be derated in practice.
Installation scope is second. A concrete pad, the automatic transfer switch, electrical tie-in, and the permit inspection commonly add $2,000 to $5,000, and that is before complications like long trench runs or strict local codes. Two identical 22kW projects in the same county can legitimately differ by that entire range.
The transfer switch itself is third. Whole-panel switches cost more than essential-circuit switches, and load-management hardware that lets a smaller generator run a bigger house sits on top of both. Bundled packages at big-box retailers shift some of this cost into the sticker, so compare what each price includes rather than the totals alone. Live pricing across the range moves week to week, so check current Generac standby generator listings before budgeting.
Generac sizes and prices versus other brands
Generac sits in the middle of the standby market on price. Kohler units generally carry a premium for quieter operation and a different dealer structure, while Champion undercuts Generac on sticker price with a thinner service network. The trade-offs get a full treatment in our Champion whole house generators guide and the Kohler dealer near you walkthrough, because service coverage at year seven matters as much as price at purchase. When you are ready to compare channels, where to buy a generator maps the dealer, big-box, and online options with their warranty implications.
FAQ
What size Generac do I need for a 2,500 sq ft house?
Most 2,500 sq ft homes with central air land on the 20kW to 22kW class. Households willing to shed the AC compressor during outages can drop to 14kW or 16kW and save $1,500 to $2,500 on equipment. Run the checklist method or the size calculator before committing either way.
How much does a 26kW Generac generator cost installed?
Typically $10,000 to $15,000 all-in, with $6,500 to $9,000 of that being the equipment. The wide installed range reflects gas line work and transfer switch choice more than regional labor alone.
Is the 7.5kW PowerPact big enough for a house?
It is big enough for a house that only needs eight circuits live: refrigerator, furnace, sump, lights, and internet. It is not a whole house solution, and its 50-amp switch cannot be stretched into one later. The standby vs portable comparison covers the smaller classes if even this feels like more than your outage history justifies.
Do Generac generators cost less on natural gas or propane?
On fuel bills, natural gas is usually cheaper per running hour and avoids tank refills. On capacity, propane is better, since every unit makes full rated power on LP and loses 10 to 15 percent on natural gas.
Bottom line
The Generac lineup answers the sizing question in clean steps: 7.5kW to 10kW for essentials, 14kW to 18kW for a family house without central air, 20kW to 22kW for most whole house coverage including AC, and 24kW to 26kW for large homes with heavy loads. Generac generator sizes and prices move together along that ladder, from about $6,000 installed at the bottom to $15,000 at the top of the air-cooled line. Size the house first with the calculator, then let three installed quotes compete inside that kW class, and the price column takes care of itself.
