Generac 7042 & 7172 Explained: /817 and /997 Shells
Reading time: ~8 min read
📋 Key Takeaways
- /817 and /997 are package codes, not model numbers. In our catalog, /817 covers the 14kW and 18kW Guardian-class air-cooled units; /997 covers the 22kW and 24kW units. The actual Generac models behind them are the 7223/7225 (14kW), 7226 (18kW), 7042 (22kW) and 7209 (24kW) families.
- NO T/SW means generator only — the "shell." It is the right buy when you already have a transfer switch or are pairing with a specific ATS. 200A SE T/SW bundles add a 200-amp service-entrance automatic transfer switch.
- The 7042 (22kW LP / 19.5kW NG) is the classic shell: 999cc G-Force engine, 67 dBA, aluminum enclosure, 5-year warranty — with no transfer switch included.
- The 7172 is the entry point: 10kW LP / 9kW NG with a 100A 16-circuit load-center switch included — sized for essentials, not whole-home.
- Size by your loads, not your square footage. 14kW covers essentials plus a small AC; 22–24kW covers most whole homes with one central AC.
Search for a Generac standby generator and you will run into listings like "22KW/997 Generac 240V 1PH NO T/SW" — which reads like a part number but is actually two separate facts glued together: the kilowatt class, and which package shell it ships in. Contractors know the shorthand; homeowners reasonably do not. This guide decodes the /817 and /997 listings we stock, maps them to the real Generac model numbers, and explains the one decision that matters most: with or without the transfer switch.
Decoding the listings
Every listing in this family answers three questions:
- kW class — 14, 18, 22 or 24kW. This is the generator's output on liquid propane; natural gas output runs slightly lower (a 22kW unit makes 19.5kW on NG).
- /817 or /997 — the shell/package family. /817 = the 14–18kW chassis; /997 = the 22–24kW chassis. Physically bigger enclosure, bigger engine.
- NO T/SW vs 200A SE T/SW — generator only, or generator bundled with a 200-amp service-entrance automatic transfer switch.
The kW classes and the models behind them
| Listing | Generac models | Output (LP / NG) | Engine | Typical coverage |
|---|---|---|---|---|
| 7172 — 10kW | 7171 (gen only) / 7172 (100A switch) | 10kW / 9kW | 460cc | Essentials circuits: fridge, furnace blower, sump, lights |
| 14KW/817 | 7223 / 7224 / 7225 | 14kW / 14kW | 816cc | Essentials + one small central AC (with soft start) |
| 18KW/817 | 7226 / 7228 | 18kW / 17kW | 816cc | Large essentials or smaller whole homes |
| 22KW/997 | 7042 / 7043 | 22kW / 19.5kW | 999cc | Whole home incl. one 3–4 ton AC |
| 24KW/997 | 7209 / 7210 | 24kW / 21kW | 999cc | Whole home with more headroom for motor starts |
Every variant is available both ways — generator-only and bundled with the 200A service-entrance ATS:
- 14kW: NO T/SW · 200A SE T/SW
- 18kW: NO T/SW · 200A SE T/SW
- 22kW: NO T/SW · 200A SE T/SW
- 24kW: NO T/SW · 200A SE T/SW
The 7042: anatomy of the 22kW shell
The Generac 7042 is the model most of the 22KW/997 searches are actually after. The spec sheet, honestly: 22,000W on propane, 19,500W on natural gas, from a 999cc G-Force engine at 3,600 RPM. Output is 120/240V single-phase — 91.7A at 240V on LP, 81.3A on NG. It sits in a RhinoCoat aluminum enclosure at 48 × 25 × 29 inches and 476 lb, runs about 67 dBA (conversation-loud at 25 feet), sips 184 cu ft/hr of NG at half load (306 at full), and self-tests weekly in the quieter low-RPM Quiet-Test mode. TruePower keeps total harmonic distortion under 5% for sensitive electronics, Wi-Fi monitoring is built in, and the warranty is 5 years limited. What it does not include is the transfer switch, the battery (Group 26R, buy locally) or the pad beyond the composite base — that is exactly what "shell" means, and it is why the shell price looks so good next to a bundled listing.
The 7172: the 10kW entry point
The Generac 7172 sits one class below the /817 family: 10kW on propane, 9kW on natural gas (41.7A / 37.5A at 240V) from a 460cc engine — and unlike the 7042 it comes with a 100A, 16-circuit load-center transfer switch. That makes it the budget-complete package for essential-circuit backup: refrigerator, furnace blower, sump pump, lights, internet, garage door. It will not carry central air conditioning; that decision pushes you to 14kW minimum and realistically 22kW.
What the install actually costs beyond the shell
The shell price is the beginning of the budget, not the end. A realistic NO T/SW install adds: the transfer switch (if not reusing one) at roughly $500–$1,500 in material, the Group 26R battery (~$150, bought locally), gas plumbing to a 3/4-inch NPT hookup sized for 306 cu ft/hr at full load on the 22kW, the pad or a poured slab, and the electrical whip, disconnect and permit. On most jobs the all-in install lands between two and three times the shell price — which is why the 200A SE T/SW bundle often pencils out better than buying the switch separately, and why a load list matters more than a square-footage guess.
Which kW class do you need?
- 10kW (7172): essentials panel only — no central AC, no electric water heater.
- 14kW (/817): essentials + a small AC with a soft starter; still a managed-load setup.
- 18kW (/817): large essentials or smaller whole homes; the overlooked middle.
- 22kW (/997, 7042/7043): the standard whole-home answer for a 2,000–3,000 sq ft house with one 3–4 ton AC.
- 24kW (/997): same homes with heavier motor starts or NG supply that would choke a 22 (remember: 22kW LP = 19.5kW NG; 24kW LP = 21kW NG).
Run your real numbers with our generator sizing calculator and the kW load calculator before choosing a class — and if you are weighing the switch bundle, the transfer switch sizing guide covers 100A vs 200A service-entrance decisions.
Frequently Asked Questions
What does "NO T/SW" mean on a Generac listing?
"No transfer switch" — you are buying the generator shell only: engine, alternator, enclosure, controller, composite pad. Choose it when you already have an ATS, are replacing a dead unit on an existing switch, or want to pair it with a specific switch bought separately. The "200A SE T/SW" variant bundles a 200-amp service-entrance automatic transfer switch.
What is the difference between the Generac 7042 and 7043?
Same 22kW/19.5kW generator; the 7043 bundles the 200A service-entrance transfer switch, the 7042 is generator-only. In our /997 listings, "NO T/SW" maps to the 7042-style package and "200A SE T/SW" to the 7043-style package.
Will a 22kW Generac run my whole house?
Most homes up to about 3,000 sq ft, yes — including one 3–4 ton central AC (ideally with a soft starter), refrigerator, furnace blower, water heater, lights and electronics, as long as the biggest motor starts are staggered. On natural gas, plan around the 19.5kW rating, not 22kW. Electric ranges and dual-AC homes should look at 24kW or load management.
Is the 7172 big enough for central air conditioning?
No. At 10kW LP / 9kW NG with a 100A 16-circuit switch, the 7172 is an essentials-circuit package: fridge, furnace blower, sump pump, lights and outlets. Central AC needs 14kW minimum with a soft starter, and 22kW for comfortable whole-home coverage.
What else do I need to buy with a NO T/SW generator?
Budget for the transfer switch (if not reusing one), a Group 26R battery, the gas plumbing hookup (3/4-inch NPT), the concrete or composite pad, and the electrical whip and disconnect. The generator ships with the composite mounting base and a flexible fuel-line connector; everything else is install material.
Know Your kW? Get the Whole Package Quoted
PES Supply stocks Generac shells and switch bundles from 10kW to 24kW, plus the batteries, pads, wire and disconnects between them — 169 authorized brands at contractor pricing. Send your load list and we will quote the complete backup system.
Shop Generators Contact Us for Bulk PricingRelated Resources
- Generator sizing calculator: running and starting watts
- What can a generator run? kW load calculator
- Transfer switch sizing guide: ATS vs manual
- Standby generator fuel consumption chart: NG, propane, diesel
- Transfer switch wire sizing: ampacity chart by kW
- Standby and portable generators
