For most homes, the right generator size depends less on square footage and more on what you want to run: essentials only, key comforts, or the whole house. As a rough guide, essentials often need about 2,000 to 4,500 watts, a small-to-medium home commonly lands around 5,000 to 10,000 watts, and whole- house standby setups often start around 15 kW to 22 kW or more.

Quick scoop

If you only want to keep the fridge, a few lights, and chargers going, a smaller portable generator may be enough. If you want to run central air, electric heat, or multiple large appliances at once, you’ll likely need a larger standby unit and a professional load calculation.

Practical sizing guide

What you want to power Typical size
Essentials only 2,000–4,500 watts
Small to medium home 5,000–10,000 watts
Mid-size home with more loads 15,000–20,000 watts
Whole-house with HVAC 15 kW–22 kW+ standby
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Best way to choose

  1. List the appliances you truly need during an outage.
  2. Add up their running watts.
  3. Add the highest starting watt surge for motors like refrigerators, sump pumps, or A/C.
  4. Choose a generator with headroom above that total.

Rule of thumb

If you’re unsure, go one size up from your estimate, especially if you have well pumps, central A/C, or electric heating. Undersizing can overload the generator and shorten equipment life.

If you want, I can help you size one exactly if you tell me your home size and the appliances you want to run.