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Generator Load Calculator

Total connected load, starting surge, and recommended generator kVA for standby power.

Total Running

13,500W

Peak Surge

32,300W

Recommended

35.53kW

Apparent Power

38.27kVA

Load Library

32 loads
Filter loads by category

  • Air Conditioner — 3 Ton

    36,000 BTU/h · 208/230 V single-phase

    3,500 W run · 17,500 W LRA · PF 0.90

  • Air Conditioner — 4 Ton

    48,000 BTU/h · 208/230 V single-phase

    4,700 W run · 23,500 W LRA · PF 0.90

  • Air Conditioner — 5 Ton

    60,000 BTU/h · 208/230 V single-phase

    5,800 W run · 29,000 W LRA · PF 0.90

  • Furnace Blower

    1/2 HP ECM · 120 V

    600 W run · 1,800 W LRA · PF 0.85

  • Heat Pump — 3 Ton

    36,000 BTU/h · scroll compressor

    3,800 W run · 19,000 W LRA · PF 0.90

  • Well Pump — 1 HP

    230 V submersible · 1 HP

    1,000 W run · 4,000 W LRA · PF 0.80

  • Well Pump — 2 HP

    230 V submersible · 2 HP

    1,900 W run · 7,600 W LRA · PF 0.80

  • Sump Pump

    1/3 HP pedestal · 115 V

    800 W run · 2,400 W LRA · PF 0.80

  • Jet Pump — 1 HP

    230 V shallow well

    1,100 W run · 4,400 W LRA · PF 0.80

  • Pool Pump — 2 HP

    230 V single-speed

    2,000 W run · 8,000 W LRA · PF 0.85

  • Walk-in Cooler

    8 × 10 ft · condensing unit

    2,200 W run · 8,800 W LRA · PF 0.85

  • Walk-in Freezer

    8 × 10 ft · low-temp condensing unit

    3,000 W run · 13,500 W LRA · PF 0.85

  • Reach-in Refrigerator

    2-door commercial · 115 V

    700 W run · 2,800 W LRA · PF 0.85

  • Ice Machine

    500 lb/day air-cooled

    1,200 W run · 4,800 W LRA · PF 0.85

  • Water Heater — 50 gal

    4,500 W resistive · 240 V

    4,500 W run · 4,500 W LRA · PF 1.00

  • Tankless Water Heater

    18 kW modulating · 240 V

    18,000 W run · 18,000 W LRA · PF 1.00

  • Boiler Circulator

    1/6 HP · 120 V

    300 W run · 900 W LRA · PF 0.80

  • Welder — 50 A

    240 V stick / MIG · 50 A input

    9,600 W run · 14,400 W LRA · PF 0.70

  • Welder — 30 A

    240 V MIG · 30 A input

    6,000 W run · 9,000 W LRA · PF 0.70

  • Plasma Cutter

    45 A · 240 V single-phase

    8,000 W run · 12,000 W LRA · PF 0.75

  • Air Compressor — 5 HP

    230 V two-stage reciprocating

    3,700 W run · 14,800 W LRA · PF 0.85

  • Air Compressor — 2 HP

    230 V single-stage

    1,500 W run · 6,000 W LRA · PF 0.85

  • EV Charger — 48 A

    11.5 kW Level 2 · 240 V

    11,500 W run · 11,500 W LRA · PF 1.00

  • EV Charger — 32 A

    7.7 kW Level 2 · 240 V

    7,700 W run · 7,700 W LRA · PF 1.00

  • UPS — 10 kVA

    Double-conversion · 0.9 PF

    9,000 W run · 9,000 W LRA · PF 0.90

  • UPS — 3 kVA

    Line-interactive · 0.9 PF

    2,700 W run · 2,700 W LRA · PF 0.90

  • Server Rack

    42U · 6 kW IT load

    6,000 W run · 6,000 W LRA · PF 0.95

  • LED Lighting Bank

    2 kW high-bay array

    2,000 W run · 2,000 W LRA · PF 0.95

  • Commercial Range

    6-burner electric · 240 V

    12,000 W run · 12,000 W LRA · PF 1.00

  • Commercial Dishwasher

    High-temp conveyor · 240 V

    5,000 W run · 5,000 W LRA · PF 1.00

  • Table Saw — 3 HP

    230 V cabinet saw

    2,200 W run · 6,600 W LRA · PF 0.85

  • Dust Collector — 2 HP

    230 V cyclone

    1,500 W run · 6,000 W LRA · PF 0.85

Connected Loads

6 selected

  • Air Conditioner — 4 Ton

    4,700 W run · 23,500 W LRA

    ea

  • Furnace Blower

    600 W run · 1,800 W LRA

    ea

  • Water Heater — 50 gal

    4,500 W run · 4,500 W LRA

    ea

  • Well Pump — 1 HP

    1,000 W run · 4,000 W LRA

    ea

  • Reach-in Refrigerator

    700 W run · 2,800 W LRA

    ea

  • LED Lighting Bank

    2,000 W run · 2,000 W LRA

    ea
Fuel Type

Recommended ATS

100 A

From 100 / 200 / 400 A

Fuel Burn @ 38%

86.95 ft³/h

1,020 BTU/ft³ · 7 in w.c. supply pressure

Natural Gas Burn Curve

  • 25%62.00 ft³/h
  • 50%110.00 ft³/h
  • 75%158.00 ft³/h
  • 100%210.00 ft³/h

Load Surge & One-Line Diagram

0k8k16k24k32kPEAK SURGE 32,300 WRUNNING 13,500 W123456LOAD INDEX · RUNNING (CYAN) / LOCKED-ROTOR SURGE (AMBER)UTILITY240 V · 60 HzTRANSFER SWITCH100 AAUTOMATICSUBPANELESSENTIAL LOADSGENERATOR 38 kVA

Worked Formula

  1. Step 1P_run = Σ (running watts × qty)P_run = 4700×1 + 600×1 + 4500×1 + 1000×1 + 700×1 + 2000×1P_run = 13,500 W
  2. Step 2P_surge = P_run + max(starting − running)P_surge = 13,500 + 18,800P_surge = 32,300 W
  3. Step 3kW = max(P_run × 1.25, P_surge × 1.10) / 1000kW = max(16,875, 35,530) / 1000kW = 35.53 kW
  4. Step 4kVA = kW / power factorkVA = 35.53 / 0.93kVA = 38.27 kVA

Standby generator sizing per NEC 702.5 and NFPA 110: the generator must carry the full connected load plus the largest motor starting surge.

NEC 220.87 · NEC 702.5 · NEMA MG 1

Hardware BOM

8 lines · 8 units
ItemSpecificationQty
Air Conditioner — 4 Ton4700 W run · 23500 W LRA48,000 BTU/h · 208/230 V single-phase1 ea
Furnace Blower600 W run · 1800 W LRA1/2 HP ECM · 120 V1 ea
Water Heater — 50 gal4500 W run · 4500 W LRA4,500 W resistive · 240 V1 ea
Well Pump — 1 HP1000 W run · 4000 W LRA230 V submersible · 1 HP1 ea
Reach-in Refrigerator700 W run · 2800 W LRA2-door commercial · 115 V1 ea
LED Lighting Bank2000 W run · 2000 W LRA2 kW high-bay array1 ea
Automatic Transfer SwitchNEC 702.5100 A · 240 V service-rated1 ea
Natural Gas Supply1,020 BTU/ft³ · 7 in w.c. supply pressure86.95 ft³/h at 38% load1 ea

Generator Load Calculator Presets

12 presets

Apply Preset Load Set