Generator Wattage Calculator – Power Requirements & Sizing
Calculate generator size requirements for appliances and equipment
Table of Contents
How to Use
- Add appliances you want to power with the generator
- Enter the running watts for each appliance (normal power consumption)
- Enter the starting watts for each appliance (startup power surge)
- Specify the quantity for each appliance type
- Click calculate to see total power requirements and recommended generator size
- The calculator includes a 25% safety buffer for efficient operation
Understanding Generator Wattage
Generator sizing requires understanding the difference between running watts and starting watts. Running watts are the continuous power needed to keep appliances operating, while starting watts are the additional power required for the initial startup surge.
Most appliances with motors (refrigerators, air conditioners, power tools) require significantly more power to start than to run. This starting surge typically lasts only a few seconds but is crucial for proper generator sizing.
Running vs Starting Watts
- Running Watts: Continuous power consumption during normal operation
- Starting Watts: Temporary power surge needed when appliances first turn on
- Motor-driven appliances: Usually need 2-3x running watts for startup
- Resistive appliances: Lights, heaters, and similar devices have equal running and starting watts
- Electronic devices: Typically have minimal starting surge requirements
Common Appliance Wattages
| Appliance | Running Watts | Starting Watts |
|---|---|---|
| Refrigerator | 150-400 | 800-2000 |
| Window Air Conditioner | 1000-1500 | 2000-4000 |
| Microwave | 1000-1500 | 1500-2000 |
| Electric Water Heater | 3000-4500 | 3000-4500 |
| Space Heater | 750-1500 | 750-1500 |
| Hair Dryer | 1200-1875 | 1200-1875 |
| Coffee Maker | 800-1200 | 800-1200 |
| Toaster | 800-1500 | 800-1500 |
| Laptop Computer | 50-100 | 50-100 |
| LED Television | 50-200 | 50-200 |
| Circular Saw | 1200-1500 | 2000-3000 |
| Drill | 500-800 | 800-1200 |
Generator Sizing Tips
- Always add a 20-30% buffer to your calculated wattage for efficiency and longevity
- Consider future appliance additions when sizing your generator
- Don't run generators at maximum capacity continuously - aim for 80% load or less
- Portable generators work best for essential circuits, not whole-house power
- Consider fuel consumption and runtime when selecting generator size
- Some appliances may not run simultaneously (calculate worst-case scenarios)
Frequently Asked Questions
- What size generator do I need for my house?
- The average home needs a 5,000-7,500 watt generator for essential circuits (refrigerator, lights, sump pump, furnace). For whole-house backup, you may need 10,000-20,000 watts depending on your home size and appliances.
- Do I need to consider starting watts for all appliances?
- No, only appliances with motors or compressors need starting watts. These include refrigerators, air conditioners, power tools, pumps, and some fans. Lights, heaters, and most electronics have equal running and starting watts.
- Why do you add a 25% buffer to the generator size?
- A 25% buffer accounts for power fluctuations, ensures efficient generator operation, extends generator life, provides headroom for future additions, and prevents the generator from running at maximum capacity which can cause premature wear.
- Can I run multiple appliances simultaneously?
- Yes, as long as their combined running watts don't exceed the generator's rated capacity. However, be careful about starting multiple motor-driven appliances at the same time, as the combined starting surge may overload the generator.
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