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How do you read this chart?
Running watts are what an appliance draws continuously while it operates. Starting watts (also called surge watts) are the brief spike a motor needs for a second or two when it starts. Generac's wattage worksheet puts it at "typically 2X running watts"; across the 47 appliances below the ratio runs from about 1.2x for electronics to about 4x for a refrigerator compressor.
To size a generator, add up the running watts of everything you want to power, then add the starting surge of the single largest motor. Add a 20% buffer on top. The values below are typical for standard residential appliances; your specific model may differ, so always check the nameplate.
How many watts do common appliances use?
Running watts and starting watts for the 47 appliances the calculator uses, grouped by category. These are the exact values behind every result on the generator size calculator; you can override any of them there with your own nameplate reading.
| Appliance | Running watts | Starting watts |
|---|---|---|
| HVAC & Cooling | ||
| Central A/C (1.5 ton) | 1,800W | 5,400W |
| Central A/C (2 ton) | 2,800W | 8,000W |
| Central A/C (3 ton) | 3,800W | 9,800W |
| Central A/C (4 ton) | 5,000W | 12,000W |
| Window A/C (5,000 BTU) | 500W | 1,500W |
| Window A/C (10,000 BTU) | 900W | 2,700W |
| Window A/C (14,000 BTU) | 1,400W | 3,800W |
| Furnace Fan (gas) | 650W | 2,000W |
| Heat Pump (2 ton) | 2,200W | 7,200W |
| Electric Space Heater | 1,500W | 1,500W |
| Whole-House Fan | 400W | 1,200W |
| Ceiling Fan | 50W | 75W |
| Essential Appliances | ||
| Refrigerator (full-size) | 300W | 1,200W |
| Chest Freezer | 150W | 600W |
| Sump Pump (½ HP) | 800W | 2,150W |
| Sump Pump (1 HP) | 1,500W | 3,900W |
| Well Pump (½ HP) | 900W | 2,500W |
| Well Pump (1 HP) | 2,000W | 5,000W |
| Oxygen Concentrator | 300W | 600W |
| CPAP Machine | 45W | 60W |
| Garage Door Opener (½ HP) | 350W | 875W |
| Sewer Ejector Pump | 800W | 2,200W |
| Kitchen Appliances | ||
| Microwave (1,000W) | 1,250W | 1,500W |
| Coffee Maker | 900W | 1,200W |
| Toaster | 1,250W | 1,500W |
| Electric Kettle | 1,350W | 1,500W |
| Dishwasher | 1,500W | 1,800W |
| Blender | 550W | 1,500W |
| Slow Cooker / Instant Pot | 500W | 1,000W |
| Electronics & Office | ||
| Laptop Computer | 70W | 100W |
| Desktop Computer + Monitor | 275W | 500W |
| WiFi Router | 15W | 20W |
| Smart TV (50") | 110W | 150W |
| Phone / Tablet Chargers | 75W | 100W |
| Cable DVR / Set-Top Box | 30W | 50W |
| Laundry & Water | ||
| Washing Machine | 750W | 2,250W |
| Gas Clothes Dryer | 500W | 1,800W |
| Electric Clothes Dryer | 5,500W | 6,000W |
| Electric Water Heater (40 gal) | 4,750W | 5,500W |
| Power Tools & Workshop | ||
| Circular Saw (7¼") | 1,400W | 2,800W |
| Electric Drill | 600W | 1,800W |
| Shop Vacuum | 975W | 2,400W |
| Air Compressor (1 HP) | 1,000W | 3,000W |
| Table Saw (10") | 1,800W | 4,500W |
| Lighting | ||
| LED Bulbs (10 bulbs) | 90W | 100W |
| LED Bulbs (20 bulbs) | 180W | 200W |
| Outdoor Flood Light (LED) | 75W | 100W |
Typical residential values, checked against the motor and non-motor load tables in the Generac Generator Sizing Guide and Generac's published generator wattage worksheet. Where the sources disagree this chart takes the higher, more conservative figure, because undersizing is what damages equipment: Generac lists a generic 0.5 HP motor at 500W running and 1,500W starting, while a real sump or well pump of that size draws 800W to 900W running and surges to 2,150W to 2,500W. Your specific model may differ, so check the nameplate.
What are the quick sizing rules of thumb?
Essentials only (fridge, lights, furnace fan, well pump, a window AC): a 5,000 to 7,500 watt portable generator is typically enough.
Whole home with central AC: you generally need a standby generator in the 12,000 to 25,000 watt range.
Workshop tools: a 5,500 to 7,500 watt portable handles most power tools, but not all at once.
What will a specific size actually run?
If you already know your generator's size and want to know which appliances it covers, these walk through real examples appliance by appliance:
- What will a 7,500 watt generator run? (plus the four common appliances that don't fit)
- What size generator for a well pump? (1/2 HP and 1 HP, plus the 240 volt catch)
- What size generator for a sump pump? (1/2 HP and 1 HP, and why storms are the worst case)
- What size generator for a fridge and freezer? (plus how long food stays safe)
Which generators match these load sizes?
| Your load (running watts) | Example model runs at | Pick it when |
|---|---|---|
| Up to 1,850W | Champion 2500-Watt Ultralight Inverter 1,850W running / 2,500W peak |
Phones, laptops, lights, a modem, a CPAP. Under 40 lb and quiet. |
| 1,850 to 3,600W | Westinghouse 4650 Peak Watt 3,600W running / 4,650W peak |
A fridge plus a furnace fan, or RV use. Has a 30A RV outlet. |
| 3,600 to 5,300W | Westinghouse 6500 Watt Dual Fuel 5,300W running on gas / 4,800W on propane |
Essentials plus a well pump or a small window AC. Transfer-switch ready. |
| 5,300 to 6,000W | Westinghouse 7500 Peak EFI Dual Fuel 6,000W running on gas / 5,400W on propane |
Essentials plus a larger AC. EFI means no choke to fiddle with. |
| 6,000 to 10,500W | DuroMax XP13000HX Dual Fuel 10,500W running / 13,000W peak |
Central AC or near whole-home. Needs a transfer switch or interlock. |
| Above 10,500W | Generac 14kW Whole Home 14,000W running, continuous |
Whole-home with no refueling. Installed by a dealer, usually quote-only. |
Once you know your running and starting watts, match them to a size bracket. Compare the generator's rated running watts against your number rather than its peak or surge rating, since running watts is the figure that limits continuous use. Each model below lists both numbers, because a generator marketed by its peak wattage often runs several thousand watts lower.
As an Amazon Associate I earn from qualifying purchases. These are size brackets, not tested recommendations. Prices and availability change; verify rated running watts against the nameplate before buying.
Get your exact size
Use the calculator to add quantities and get a precise recommendation with the math shown.
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Disclaimer: These are typical values for planning purposes only. Actual wattage varies by make, model, and age of your appliances. Always check the nameplate (label) on each appliance for its true running and starting watts, and consult a licensed electrician before installing or connecting a generator. Never run a generator indoors.