Generator Load Reference Chart — Whole-Home Watts by Circuit
The reference table PES account reps use to size Generac, Cummins, Briggs & Stratton, and Kohler standby generators. Continuous watts and motor-start surge for every common residential and light-commercial load, plus the standard kW ladder and the transfer-switch, fuel-line, and pad-size decisions that follow from it.
This page is the reference our account reps and installers turn to when a spec has to be defended in front of a homeowner or a general contractor: continuous watts by circuit, motor-start surge on the biggest inductive loads, the standard kW ladder that Generac, Cummins, Briggs & Stratton, and Kohler actually manufacture, and the transfer-switch, fuel-line, and pad-size decisions that follow. If you want the interactive version that lets you enter your job and get a recommended kW plus brand options in one screen, use the contractor portal generator sizing calculator — free with contractor account registration.
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These are the numbers our account reps sum when a contractor calls with a new residential job. Continuous watts is what the appliance draws while running; motor-start surge is the extra draw for the first few seconds when an inductive load (an AC compressor, a well pump, a large refrigerator) energizes. The starting watts number is what your standby generator has to swallow in that instant. Add continuous watts across every appliance that could be running simultaneously, then add the single largest motor-start surge on top — that is the peak load.
| Load | Continuous Watts (Running) | Motor-Start Surge (Additional) | Category |
|---|---|---|---|
| Central AC — 2 ton | 2,500 | 4,500 | HVAC |
| Central AC — 3 ton | 3,600 | 6,000 | HVAC |
| Central AC — 4 ton | 4,800 | 7,500 | HVAC |
| Central AC — 5 ton | 6,000 | 9,000 | HVAC |
| Heat pump — 3 ton (with resistive strip) | 7,600 | 6,000 | HVAC |
| Furnace blower / air handler | 800 | 1,200 | HVAC |
| Electric water heater — 50 gal (4,500W element) | 4,500 | — | Water |
| Electric water heater — 80 gal (5,500W element) | 5,500 | — | Water |
| Well pump — ½ hp | 1,000 | 2,000 | Water |
| Well pump — 1 hp | 1,500 | 3,000 | Water |
| Well pump — 2 hp | 2,400 | 4,800 | Water |
| Sump pump | 1,050 | 2,200 | Water |
| Electric range — 4 burners + oven | 5,000 | — | Kitchen |
| Electric range — 2 burners + oven | 3,500 | — | Kitchen |
| Refrigerator (standard) | 700 | 1,400 | Kitchen |
| Chest freezer | 500 | 1,000 | Kitchen |
| Microwave (1,000W-class) | 1,500 | — | Kitchen |
| Dishwasher (with heater) | 1,500 | — | Kitchen |
| Electric dryer | 5,500 | — | Laundry |
| Gas dryer (fan + igniter) | 700 | — | Laundry |
| Clothes washer | 1,150 | 2,300 | Laundry |
| EV charger — Level 2, 30 A | 7,200 | — | EV |
| EV charger — Level 2, 40 A | 9,600 | — | EV |
| EV charger — Level 2, 48 A | 11,500 | — | EV |
| Hot tub / spa (240 V, 4 kW heater) | 4,000 | — | Comfort |
| Whole-home lighting (LED) | 400 | — | General |
| Whole-home lighting (mixed) | 1,200 | — | General |
| Electronics + receptacles baseline | 1,500 | — | General |
| Garage door opener | 400 | 800 | General |
| Central vacuum | 1,400 | 2,800 | General |
The sizing math sums every continuous load — lights, receptacles, refrigeration, EV charging, water heater, electric range, electric dryer — into a single continuous watts figure. Then take the single largest inductive load (the biggest AC compressor or well pump) and add its motor-start surge on top. That combined peak is what the generator has to swallow the instant that compressor kicks in on a warm evening. That peak is then de-rated for fuel: natural gas loses about 10% of rated capacity versus liquid propane, so the required kW is scaled up 1.10× on NG. Finally, the result is rounded up to the next standard kW size on the 8–200 kW ladder that at least one of the four major brands stocks. The interactive calculator on the PES contractor portal runs this math for you and cross-references the sized kW against real Generac, Cummins, Briggs & Stratton, and Kohler product families.
Worked example — 3,800 sq ft mixed-fuel home in Kentucky
- Continuous baseline: 8,000 W (lights, fridge, receptacles).
- 3-ton AC compressor: 3,600 W run, plus 1,600 W of start surge above run.
- 1 hp well pump: 1,500 W run.
- Electric range: 3,500 W (in use during outage).
- Electric dryer: 5,500 W (assume in use).
- Electric water heater: 4,500 W.
- EV charger: 0 (customer confirmed unplugs during outage).
- Continuous = 26,600 W. Peak with 3-ton start surge = 28,200 W. NG derate ×1.10 = 31,020 W ≈ 31.0 kW → rounded up to 36 kW liquid-cooled (Generac Protector RG03616 or Cummins C40).
Standby generators are not made in every kW size. They come in a fixed ladder because that is how the OEMs manufacture engine and alternator combinations. The calculator rounds up to the next size on this ladder:
| kW Rung | Class | Typical Brands at This Size |
|---|---|---|
| 8 kW | Air-cooled residential (entry) | Generac Guardian, Briggs residential |
| 10 kW | Air-cooled residential | Generac 10 kW, Briggs 10 kW |
| 12 kW | Air-cooled residential | Generac 7175 (12 kW) |
| 14 kW | Air-cooled residential | Kohler 14RESA, Generac 14 kW |
| 16 kW | Air-cooled residential | Generac 16 kW |
| 20 kW | Air-cooled residential | Kohler 20RESA, Generac 20 kW, Briggs 20 kW |
| 22 kW | Air-cooled residential (volume seller) | Generac 7043, Cummins QC22, Briggs 22 kW |
| 24 kW | Air-cooled residential | Kohler 24RCL, Generac 24 kW |
| 26 kW | Air-cooled residential (top of class) | Generac 7291, Kohler 26RESV, Briggs 26 kW |
| 30 kW | Liquid-cooled commercial (entry) | Generac Protector RG03015, Kohler 30REZG, Briggs Fortress 30, Cummins C30 |
| 36 kW | Liquid-cooled | Generac Protector RG03616, Cummins C40 |
| 40 kW | Liquid-cooled | Cummins C40, Briggs Fortress 40 |
| 45 kW | Liquid-cooled | Briggs Fortress 45, Kohler 48REZG |
| 48 kW | Liquid-cooled | Generac Protector RG04854, Kohler 48REZG |
| 50 kW | Liquid-cooled | Cummins C50 |
| 60 kW | Light commercial | Generac SG060, Kohler 60REZG, Briggs Fortress 60, Cummins C60 |
| 80 kW | Commercial | Kohler 80REOZJ, Cummins C80, Generac Industrial 80 |
| 100 kW | Commercial | Kohler 100REOZK, Cummins C100, Generac Industrial 100 |
| 125 kW | Commercial | Kohler 125REOZK, Cummins C125, Briggs Fortress 125 |
| 150 kW | Commercial/industrial | Kohler 150REOZK, Generac Industrial 150 |
| 200 kW | Industrial | Cummins C200 D6, Kohler 200REOZK |
The recommended kW is the floor of what will run the site through a worst-case outage evening — the moment everything cycles on together. Two adjustments contractors typically make on top of the calculator:
Add 10-15% headroom for future load growth
If the customer might add an EV charger in year 2, a hot tub in year 3, or a second AC compressor when the addition is built, add 15% before rounding to the next kW. That usually moves a borderline 22 kW spec to a 26 kW, or a 48 kW commercial spec to a 60 kW.
Down-size if intelligent load management is on the plans
Generac Smart Management Modules (SMM) or equivalent load-shed relays let a 22 kW cover a house that raw math says needs 26 kW — the AC and the dryer can't both run at once. If SMM is in the spec, subtract the smaller of the two loads before sizing.
Confirm the ATS amperage matches the service panel
A 200A residential service panel needs a 200A service-entrance ATS for whole-home coverage. Don't spec a 100A ATS for a whole-home config — either upsize the ATS or move to load-shed with a smaller ATS. The two options price differently.
Verify NG meter capacity before finalizing
Utility gas meters at older homes are often 250 CFH — enough for a 14–16 kW generator but not a 22–26 kW under full load. Confirm meter capacity with the utility before locking the model number. Meter upsize is a permit and a utility appointment, not a same-week job.
Once the recommended kW is set, the fastest path to a real quote is to register for a contractor account. Tier-1 accounts see distributor pricing on every unit and OEM part on the site, get a named account rep for pallet buys and single-project bundles, and unlock the interactive generator sizing calculator plus voltage-drop, wire-sizing, and freight calculators on the contractor portal.
Open a contractor account with PES Supply
Get pallet-quantity pricing, tier discounts, and drop-ship freight on Generac, Cummins, Briggs & Stratton, and Kohler standby generators — plus access to the interactive sizing, voltage-drop, wire-sizing, and freight calculators on the PES contractor portal.
Register for contractor pricing →Registered contractors — access the interactive calculators on the PES contractor portal
- Generator Sizing Calculator — spec kW, ATS, fuel line, and pad in one screen
- Voltage Drop Calculator — NEC 210.19(A) informational note conductor sizing
- Wire Sizing Calculator — NEC 310.16 ampacity with derating
- Freight Calculator — pallet-quantity freight quotes 48 states
