Most homes need a generator in the 5,000 to 9,000 running watt range to power essential circuits comfortably, depending on whether you include major motor loads like a sump pump or well pump.
Build your load list quickly with the WattSizing Calculator.
Quick Answer
For a typical essential-circuits panel (refrigerator, lights, internet, outlets, and furnace blower), a 6,000 to 7,500 watt generator is a practical starting point.
If you add larger motor loads (well pump, sump pump, larger freezer), expect to size up into the 7,500 to 10,000+ watt range.
What Counts as "Essential Circuits"?
Most homeowners include:
- Refrigerator and/or freezer
- Kitchen and hallway lights
- Internet modem + router
- A few general-use outlets
- Furnace blower or boiler controls
- Sump pump or well pump (if applicable)
The biggest sizing mistake is treating this as only running watts. Motor-based loads can start at much higher wattage for a short time.
Essential Circuits Sizing Table
| Essential Circuit Group | Typical Running Watts | Typical Starting Watts |
|---|---|---|
| Core essentials (fridge, lights, internet, outlets) | 700 - 1800 W | 1200 - 2600 W |
| Core + furnace blower | 1200 - 2600 W | 2200 - 4200 W |
| Core + sump pump | 1300 - 3000 W | 3000 - 5500 W |
| Core + freezer + furnace blower | 1500 - 3200 W | 2600 - 5000 W |
| Core + well pump + freezer | 1800 - 3800 W | 4200 - 7500 W |
If your plan includes electric water heating, check What Size Generator for Electric Water Heater, since that load can dominate your total.
Calculation Example
Example essential panel:
- Refrigerator: 250 W running / 800 W start
- Freezer: 400 W running / 1,100 W start
- Furnace blower: 700 W running / 1,400 W start
- Lighting + internet + outlets: 500 W running / 600 W start
- Sump pump: 900 W running / 2,200 W start
Step 1: Running total
250 + 400 + 700 + 500 + 900 = 2,750 W
Step 2: Largest surge gap
Sump pump surge gap = 2,200 - 900 = 1,300 W
Step 3: Startup-capable requirement
2,750 + 1,300 = 4,050 W
Step 4: Add 25% headroom
4,050 x 1.25 = 5,060 W
Practical selection: 5,500 to 6,500 running watts, with enough surge rating for motor starts.
Practical Selection Rules
- Prioritize clean 120V output and sufficient surge handling.
- Choose a model that can run at 50 to 80% load during normal backup.
- If you need both 120V and 240V loads, confirm split-phase capability.
- Use a transfer switch/interlock and have a licensed electrician verify layout.
FAQs
Is a 7,500 watt generator enough for most homes' essentials?
For many homes, yes. It often covers refrigeration, lighting, internet, and one or two motor loads if managed well.
Can I run central AC on an essential-circuits generator?
Usually not on smaller essential-only setups. Central AC often pushes you into a much larger standby class.
Should I include every outlet in the house?
No. Start with true essentials and only add circuits with clear outage value.
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