What Size Generator Do I Need for My House? (Wattage Chart)
The list, with sourced watts
| Appliance | Running watts | Starting (surge) |
|---|---|---|
| Refrigerator/freezer (standard household) | 1,000 | 2,200 |
| Chest / deep freezer | 720 | 1,890 |
| Sump pump (1/3 HP) | 800 | 2,100 |
| Well pump (1/2 HP) | 1,000 | 2,100 |
| Furnace fan blower (1/2 HP) | 1,100 | 2,350 |
| Window AC (10,000 BTU) | 1,200 | 2,000 |
| Microwave oven (1000 W cook power) | 1,000 | 2,000 |
| TV, LED flat-screen | 190 | — |
| Wi-Fi router + modem | 20 | — |
| Cell phone charger | 25 | — |
| Coffee maker | 1,200 | — |
| Washing machine | 1,150 | 3,450 |
| Electric water heater (40-gal tank) | 5,500 | — |
| Central AC (36,000-40,000 BTU / 3+ ton) | 6,000 | 7,200 |
Essentials — ~4,700W
Spec: manufacturer
As an Amazon Associate, needwatts.com earns from qualifying purchases. Links below are affiliate links — this never affects our wattage math or which units we list.
See Westinghouse WGen5300 on Amazon →Spec: authorized_dealer
As an Amazon Associate, needwatts.com earns from qualifying purchases. Links below are affiliate links — this never affects our wattage math or which units we list.
See Honda EU7000iS on Amazon →Comfort — ~9,600W
Spec: manufacturer
As an Amazon Associate, needwatts.com earns from qualifying purchases. Links below are affiliate links — this never affects our wattage math or which units we list.
See Westinghouse WGen9500DF on Amazon →Spec: manufacturer
As an Amazon Associate, needwatts.com earns from qualifying purchases. Links below are affiliate links — this never affects our wattage math or which units we list.
See DuroMax XP13000EH on Amazon →Near-whole-home — ~27,900W
No unit in our verified catalog cleanly covers this load — see the calculator to adjust your list.
The arithmetic
+ largest single starting surge: 2,300W
= peak demand: 23,205W
× 1.2 headroom → recommended rating: ~27,900W
Adjust this list in the calculator →
What size generator do I need for my house?
Essentials ~4,700W; comfort ~9,600W; near-whole-home ~27,900W. Size to the loads you actually run at once, not the house.
Can I size a generator by square footage?
No. Generators size by electrical load, not floor area — a small house with a well pump and electric water heater needs more than a large house on gas. Add up your actual appliances.
Why do starting watts matter?
Motor-driven appliances briefly draw 2–4× their running watts at startup. Cover the running total plus the single largest surge, or the motor stalls.
Sources
- Wattage Worksheet '3R0WATTGUIDE' (generator reference guide, Home Depot-hosted PDF) (vendor)
- A-iPower Wattage Chart (Sam's Club-hosted PDF) (vendor)
- Champion Power Equipment 'Choosing a Generator' wattage flyer (manufacturer)
- Howell-Oregon Electric Cooperative generator sizing chart (utility)
- Grounded Electric generator wattage chart (licensed electrical contractor) (vendor)
- Midwest Electric Cooperative Corp. wattage page (citing U.S. DOE EERE) (utility)
Figures are conservative sizing values chosen from the range these sources report. Your appliance's nameplate is authoritative.