How to use this calculator
Check the box next to each appliance you want your generator to power. The calculator uses standard wattage values, but you can click Edit on any selected item to adjust the running watts, starting watts, or quantity to match your specific equipment.
If your appliance is not in the list, use the custom item section at the bottom to add it. Check the nameplate on your equipment or the owner manual for exact wattage figures.
The recommended generator size equals your total running watts plus the largest single starting surge, then multiplied by 1.2 for a 20% safety margin. This ensures your generator can handle both continuous loads and startup demands without overloading.
Understanding generator sizing
| Generator Tier | Wattage Range | Best For |
|---|---|---|
| Portable | 1,000 to 4,000W | Camping, tailgating, a few essentials during outages |
| Mid Size | 4,000 to 7,500W | Most household circuits, window AC, fridge, lights, and electronics |
| Large Portable | 7,500 to 12,000W | Nearly all home appliances running at the same time |
| Whole House Standby | 12,000 to 20,000W+ | Full home coverage including central AC and electric cooking |
Frequently asked questions
How do I calculate the wattage I need for a generator?
Add up the running watts of every appliance you plan to use simultaneously. Then identify the single appliance with the highest starting surge and add that extra draw to your total. A 20% safety buffer on top ensures the generator never operates at full capacity for extended periods, which protects the engine and extends its lifespan.
What is the difference between starting watts and running watts?
Running watts are the continuous power an appliance consumes during normal operation. Starting watts are the short burst of extra power needed to start motor driven devices such as refrigerators, pumps, and air conditioners. This surge typically lasts only a few seconds but can be two to three times the running wattage. Your generator must be able to handle this peak demand.
What fuel type is best for a home generator?
It depends on your situation. Gasoline is cheap and easy to find but degrades in storage. Propane stores indefinitely and burns cleaner, making it great for standby use. Diesel is the most fuel efficient option for heavy, continuous loads. Dual fuel generators that accept both gasoline and propane give you the most flexibility during extended power outages.
What safety precautions should I follow when using a generator?
Always run generators outdoors, at least 20 feet from your home, with the exhaust pointing away from windows and doors. Carbon monoxide poisoning is the number one risk. Use a transfer switch instead of plugging directly into a wall outlet, which is called backfeeding and can electrocute utility workers. Install battery powered carbon monoxide detectors near sleeping areas for added protection.