Buying a generator that is too small trips its overload breaker the moment your refrigerator compressor or sump pump kicks on. Buying one that is twice as large as you need wastes fuel and money. The secret to sizing backup power accurately is understanding Running Watts vs. Starting Surge Watts—and matching your equipment to how long blackouts actually last in your ZIP code.
⚡ Always size for Starting Surge Watts—not just Running Watts: Electric motors in refrigerators, furnace blowers, sump pumps, well pumps, and air conditioners draw 2x to 3.5x their running wattage for a split second when starting up. Check your ZIP code outage report & interactive wattage sizer to calculate both running and peak surge watts for your home.
Typical Home Appliance Running & Surge Wattage Chart
| Appliance / Circuit | Running Watts | Starting Surge Watts | Why Surge Matters |
|---|---|---|---|
| Refrigerator / Freezer (Modern Energy Star) | 150W – 250W | 1,000W – 1,400W | Compressor motor spikes 5–6x when cycling on every 30–45 minutes. |
| Gas or Propane Furnace Blower Fan (1/2 HP) | 600W – 800W | 1,400W – 1,800W | Even gas furnaces need 120V electricity for the blower motor, control board, and igniter. |
| Basement Sump Pump (1/3 to 1/2 HP) | 750W – 1,050W | 1,800W – 2,400W | Starts under heavy water head pressure during severe rainstorms. |
| Deep Well Water Pump (1/2 to 3/4 HP, 240V) | 1,000W – 1,500W | 2,200W – 3,500W | Requires a 240V generator output (NEMA L14-30R) to power both legs of your well breaker. |
| Window or Portable AC Unit (10,000 BTU) | 1,000W – 1,200W | 2,200W – 2,600W | High compressor startup draw during summer heatwaves. |
| Central Air Conditioner (3-Ton, 240V) | 3,500W – 4,200W | 7,500W – 10,500W | Adding a $300 soft-start kit cuts central AC startup surge by up to 65%. |
| Microwave / Coffee Maker / Toaster | 1,000W – 1,500W | 1,000W – 1,500W | Purely resistive heating load (zero extra surge, but high continuous draw). |
| Wi-Fi Router, Laptop, Phone Chargers & LED Lights | 100W – 200W | 150W – 200W | Low continuous draw; sensitive electronics prefer pure sine wave power. |
3 Backup Power Tiers by Wattage & Outage Duration
- Tier 1 — Essential Indoor Backup (1,000W – 2,200W): Ideal when your ZIP code SAIDI is under 4 hours/year or you live in an apartment/condo. A LiFePO4 portable power station runs your refrigerator, Wi-Fi router, phones, CPAP, and LED lights for 12–24 hours indoors with zero carbon monoxide fumes.
- Tier 2 — Mid-Size Storm & Furnace Backup (3,500W – 5,000W): Ideal for suburban homes on city water. A quiet dual-fuel inverter generator (or expandable home battery) comfortably powers your refrigerator, gas furnace blower fan, basement sump pump, microwave, and electronics.
- Tier 3 — Whole-Home Critical Circuits (7,500W – 12,000W, 240V): Essential for homes with a 240V well water pump, multi-day ice/hurricane outage risk, or central air conditioning. Pair with a 30-amp or 50-amp manual transfer switch or breaker interlock kit.
EcoFlow DELTA 2 / DELTA Pro LiFePO4 Portable Power Stations
1,800W to 3,600W pure sine wave output with 10-year LiFePO4 battery chemistry—plug in your fridge, Wi-Fi, and CPAP indoors.
Westinghouse WGen7500DF / WGen9500DF Dual-Fuel Home Generators
Runs on gasoline or propane with push-button electric start and a 240V L14-30R transfer-switch outlet for whole-home backup.