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how big generator to run house

For most homes, the right generator size depends on whether you want to power everything or just the essentials, but many typical houses land somewhere in the 10,000–20,000 watt (10–20 kW) range for whole‑home coverage.

Quick Scoop: Typical Generator Sizes

  • Small homes or “essentials only” (lights, fridge, some outlets, maybe gas furnace blower) often do fine with about 5,000–10,000 watts.
  • Average homes aiming for whole‑house backup usually need about 10,000–20,000 watts , depending on square footage and big loads like electric ranges, well pumps, or central AC.
  • Larger houses or homes with multiple HVAC units, electric water heaters, or luxury loads (pool, hot tub, EV charger) can push into the 22,000–30,000+ watt range.

Rule of Thumb by House Size

These are ballpark figures; local codes and your exact appliances matter.

  • Under ~1,500–2,000 sq ft, focusing on essentials: around 7–10 kW can cover basic loads.
  • Around 1,500 sq ft, full‑house coverage often needs roughly 15–16 kW.
  • About 2,000–3,000 sq ft: 15–22 kW is common for running most appliances and at least one HVAC system.
  • 3,000+ sq ft: 22–30+ kW if you want “almost normal life” during an outage, including AC, electric ovens, and pumps.

Simple Step‑By‑Step Sizing Method

  1. Decide: essentials vs whole house
    • Essentials only → fridge(s), freezer, lights, internet, maybe gas furnace blower, sump pump or well pump. This keeps the generator smaller and cheaper.
 * Whole house → everything you normally use: HVAC, electric stove, dryer, water heater, etc. This pushes you toward 15–30 kW (or more in big homes).
  1. List your big loads
    • Central AC, electric range, oven, electric dryer, electric water heater, well or sump pump, pool equipment, EV charger all have high wattage and starting surges.
 * If you drop one or two of these during outages, you can choose a smaller generator.
  1. Add up running watts, then allow for starting watts
    • Each appliance has a watt rating; many motors (AC, pumps) need extra “surge” power for a few seconds when they start.
 * A common approach:
   * Add up the **running watts** of what you want on at the same time.
   * Make sure the generator also covers the **highest starting load** (often a big motor like AC or a pump).
  1. Pick a generator with headroom
    • Most pros recommend a unit that is slightly larger than your calculated needs, so it is not always at 100% load and has room for small extras.

Portable vs Standby for a House

  • Portable generator (5–10 kW)
    • Good for essentials in a typical home.
    • Needs manual refueling and usually manual hookup (ideally via a transfer switch).
  • Whole‑house standby generator (10–30+ kW)
    • Permanently installed, automatic, and usually sized to match your total planned load.
* Best if you face frequent or long outages and want near‑normal living.

Practical Recommendation

  • If you just want the bare essentials during an outage in an average‑size house, target around 5–10 kW and plan which circuits are backed up.
  • If you want your whole house to feel close to normal , plan for roughly 15–25 kW , then have an electrician do a load calculation to confirm the exact size and meet code.

Information gathered from public forums or data available on the internet and portrayed here.