Portable generator load calculator
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To purchase the right generator for home , work or camping, you’ll need to know the wattage of the all appliances you plan to run. First, verify the owner’s manual and serial plate on your appliance for the wattage (or watts) rating. If wattage is not listed, find the amperage (amps) and voltage (volts) ratings on the same plate. Multiply amps by volts to get the wattage.
If the rated/running watts are not on appliance, you may estimate using the following equation: WATTS=VOLTS x AMPS.
Only motor-driven items will have an additional surge requirement. The additional surge watts required may be estimated at 1 – 2x the rated/running watts.
Unlike rated watts, surge watts are only needed during the first few seconds of operation. In most cases, only one item will start or cycle at the same time, therefore this is the most accurate estimate.
The table below shows you rated and surge watt totals separately to help you determine which tool or appliance represents your total wattage requirement.
Determine power generator
- To determine your needs, total the watts for the items you would like to run simultaneously. This provides you with the number of continuous or running watts your generator must supply.
- Now select the largest number of starting watts assigned to the items you wish to use.
- Total these two numbers and this will indicate the size generator required to meet your needs.
| TOOL OR APPLIANCE | RATED (RUNNING) WATTS | ADDITIONAL SURGE (STARTING) WATTS |
| HOME | ||
| Light Bulb – 75 Watt | 75 | |
| Deep Freezer | 500 | 500 |
| Sump Pump | 800 | 1200 |
| Refrigerator/Freezer | 800 | 1600 |
| Water Well Pump 1/3 HP | 1000 | 2000 |
| HEATING/ COOLING | ||
| Space Heater | 1800 | – |
| Table Fan – 14″ | 200 | 400 |
| Ceiling Fan | 800 | 1200 |
| Furnace Fan Blower 1/2 HP | 800 | 1300 |
| Window AC – 10000 BTU | 1200 | 1800 |
| Window AC – 12000 BTU | 3250 | 3950 |
| Central AC – 10000 BTU | 1500 | 4500 |
| Heat Pump | 4700 | 4500 |
| Space Heater | 1800 | – |
| KITCHEN | ||
| Microwave Oven – 1000 Watt | 1000 | – |
| Coffee Maker | 1500 | – |
| Electric Stove – Single Element | 1500 | – |
| Dishwasher – Hot Dry | 1500 | 1500 |
| FAMILY ROOM | ||
| DVD/CD Player | 100 | – |
| VCR | 100 | – |
| Stereo Receiver | 450 | – |
| Color Television – 27″ | 500 | – |
| LAUNDRY ROOM | ||
| Iron | 1200 | – |
| Washing Machine | 1150 | 2250 |
| Clothes Dryer | 5400 | 1350 |
| OFFICE EQUIPMENT | ||
| Personal Computer | ||
| with 17″ Monitor | 800 | – |
| Fax Machine | 65 | – |
| Laser Printer | 950 | – |
| Inkjet Printer | 80 | – |
| Copy Machine 1 | 600 | – |
| OTHER | ||
| Security System | 180 | – |
| AM/FM Clock Radio | 100 | – |
| Garage Door Opener – 1/2 HP | 480 | 520 |
| Hair Dryer – 1250 Watt | 1250 | – |
| Electric Water Heater -40 Gallon | 4000 | – |
| DO-IT-YOURSELF JOBSITE | ||
| Quartz Halogen Work Light | 1000 | – |
| Airless Sprayer – 1/3 HP | 600 | 1200 |
| Reciprocating Saw | 960 | – |
| Electric Drill – 1/2 HP | 1000 | 1000 |
| Circular Saw – 7 1/4″ | 1500 | 1500 |
| Miter Saw – 10″ | 1800 | 1800 |
| Planer/Jointer – 6″ | 1800 | 1800 |
| Table/Radial Arm Saw 10″ | 2000 | 2000 |
| Air Compressor – 1 1/2 HP | 2500 | 2500 |
Data listed above are estimates only. Verify your tool or appliance for exact wattage requirements. The wattages listed in our reference guide are based on estimated wattage requirements.
