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what size generator do i need for my home

For most homes, you’ll need somewhere between about 5,000 and 20,000 watts (5–20 kW) of generator capacity, depending mainly on your house size and how many big appliances you want to run during an outage. To get it right, you’ll need to decide whether you’re just covering essentials (fridge, a few lights, maybe a small A/C) or trying to power almost everything as usual.

Quick Scoop: Typical Sizes by Home

Use this as a rough ballpark; exact needs depend on your actual appliances and climate:

  • Small home or “essentials only” (basic lights, fridge, electronics, maybe a small window A/C): often 5,000–8,000 watts (5–8 kW).
  • Average home, more comfort (fridge, lights, well pump or sump pump, one central A/C or furnace blower, a few outlets): usually 10,000–20,000 watts (10–20 kW).
  • Large home or “whole‑house” with central A/C and many circuits: commonly 20,000–25,000+ watts (20–25+ kW).

One example guide suggests small homes under about 1,500 square feet often get by with around 7–10 kW, midsized homes between roughly 1,500 and 3,000 square feet often use around 17–20 kW, and larger homes over 3,000 square feet may need 22–25 kW or more.

Step‑by‑Step: How to Size Your Generator

Think of it like packing a suitcase: list what must “fit” during an outage, then check how big a suitcase you need.

  1. List what you must power
    • Examples:
      • Refrigerator or freezer
      • Lights in a few key rooms
      • Wi‑Fi, phone chargers, a TV or computer
      • Sump pump / well pump
      • Furnace blower or boiler
      • One A/C (central or window) if you’re in a hot climate
    • The more big loads you add (A/C, electric water heater, electric oven, well pump), the bigger the generator.
  1. Find running watts for each
    • Look at appliance labels or manuals; they list watts or amps (amps × volts ≈ watts).
 * Add up all the _running_ watts for the things you plan to have on at the same time.
  1. Check starting (surge) watts
    • Motors (fridges, A/C, pumps) use more power when they start.
    • For example, a fridge might run at about 600 watts but need about 1,200 watts to start; a central A/C might run at about 2,000 watts but need up to about 4,000 watts at start.
 * Find the highest starting watt requirement among your listed items and add that one extra on top of your total running watts.
  1. Add a safety margin
    • A common rule of thumb: after you’ve done your math, add about 20% on top for safety and future devices.
 * This helps avoid tripping the generator when several big loads kick on at once.
  1. Compare your total to generator “size ranges”
    • Some buying guides group generators by what they can support:
   * 500–3,000 W: camping, small tools, very basic loads.
   * 3,100–6,000 W: some appliances plus a small A/C or heat.
   * 6,100–10,000 W: more full‑featured emergency power for larger appliances, water heater, heating or cooling.
   * 10,100 W and up: whole‑home–style backup for many circuits.

Tiny story example:
Imagine you just want to keep the fridge cold, a few lights on, and charge your phone. You add everything up and land around 2,500 running watts with one fridge that needs 1,200 surge watts. Your total is about 3,700 watts; with a ~20% buffer, you’re looking at something in the 4,500–5,000‑watt class so it’s not “packed to the zipper” every time the fridge starts.

Portable vs Standby (Whole‑House)

Different generator types cover different “levels of normal life” during an outage.

Portable generators

  • Usually in the 2,000–10,000‑watt range, powered by gasoline or propane.
  • Great if you want to run only essentials and are okay with refueling and running extension cords or a manual transfer switch.
  • Cheaper upfront, but you must start them manually and manage the load yourself.

Standby (whole‑house) generators

  • Permanently installed outside; they turn on automatically when utility power fails.
  • Typical home standby systems run from about 10 kW up to 25 kW or more, sized to your house and what you want to run.
  • Better if outages are frequent or long, or if you need medical equipment, sump pumps, or heating/cooling to stay on without babysitting the system.

Some guides note that most single‑family homes land somewhere between about 5,000 and 25,000 watts total need once you add up all the realistic loads you’ll use in an outage.

Quick HTML Table: Approximate Home Generator Sizes

Here’s a simple starting‑point chart (not a substitute for a professional load calculation):

html

<table>
  <thead>
    <tr>
      <th>Home / Usage Type</th>
      <th>Approx. Generator Size</th>
      <th>Typical Use Case</th>
    </tr>
  </thead>
  <tbody>
    <tr>
      <td>Small home or essentials-only setup</td>
      <td>5,000–8,000 W (5–8 kW) [web:3][web:5]</td>
      <td>Fridge, lights, phone/TV, maybe small A/C or window unit</td>
    </tr>
    <tr>
      <td>~1,500 sq ft home</td>
      <td>10,000–15,000 W (10–15 kW) [web:3]</td>
      <td>Essentials plus well pump/sump pump, some HVAC capacity</td>
    </tr>
    <tr>
      <td>~2,000 sq ft home</td>
      <td>16,000–20,000 W (16–20 kW) [web:3][web:1]</td>
      <td>Most circuits, central A/C or electric heat (managed)</td>
    </tr>
    <tr>
      <td>~2,500 sq ft home</td>
      <td>18,000–22,000 W (18–22 kW) [web:3]</td>
      <td>Near whole-home coverage for many families</td>
    </tr>
    <tr>
      <td>3,000+ sq ft home</td>
      <td>23,000–25,000+ W (23–25+ kW) [web:1][web:3]</td>
      <td>Whole-home power, multiple HVAC systems, many circuits</td>
    </tr>
    <tr>
      <td>Recreation / light-duty portable</td>
      <td>500–3,000 W [web:5][web:9]</td>
      <td>Camping, small tools, a couple of small appliances</td>
    </tr>
    <tr>
      <td>General portable home backup</td>
      <td>3,100–10,000 W [web:5]</td>
      <td>Emergency power, some heating/cooling, larger appliances</td>
    </tr>
  </tbody>
</table>

Real‑World Forum Angle

People in generator forums often report underestimating how much A/C, well pumps, and electric water heaters add to their load, because these all have both high running and high starting wattage. Many users end up recommending that you either:

  • Buy a slightly larger unit than your first estimate (to avoid constantly running at max load), or
  • Use a smaller generator but be disciplined about what you run at the same time (for example, don’t run the electric oven while the A/C and well pump are both on).

A common theme in discussions is that if you want “hands-off” convenience with central A/C, it’s usually easier to step up in size or install soft‑start kits on big loads so the generator doesn’t get slammed by high inrush currents.

When to Call a Pro

Even with the rules of thumb above, a licensed electrician or generator installer is the safest way to get a precise answer. They can:

  • Perform a load calculation on your panel and major appliances.
  • Factor in local code, transfer switch type, and whether you plan to add EV chargers, hot tubs, or other big loads later.
  • Help you balance “big enough not to struggle” with “not so large that you overspend and run inefficiently”.

TL;DR

  • Most homes end up needing somewhere in the 5–20 kW range, depending on size and how many big appliances you want to run.
  • Make a list of essentials, add up running watts, add the highest starting watts, then add about 20% safety margin to choose a size.
  • For exact sizing—especially if you want true whole‑house backup—have an electrician do a proper load calculation.

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