A portable generator in the 7,500–12,500 running watt range will power most houses, because that window covers the biggest load in most homes — a central air conditioner — plus a refrigerator, well pump, and lights simultaneously.

The right size depends on what you actually need to run at the same time. A 7,500W running watt generator handles a smaller home with one AC zone, a refrigerator, and basic lights. Step up to 10,000–12,500 running watts — like the DuroStar DS13000MX at 10,500 running watts — and you have enough headroom for a 3-ton central AC (3,000W running, ~5,000W startup surge), a full-size refrigerator, a well pump, and several additional outlets without tripping the generator's own breaker.

  • Whole-house essentials (AC, refrigerator, well pump, lights) typically require 5,000–8,500 running watts combined.
  • A 3-ton central AC compressor needs roughly 5,000 starting watts and 2,000–3,500 running watts.
  • The DuroStar DS13000MX delivers 10,500 running watts and 13,000 peak watts — enough for most full-home backup loads.
  • Peak (starting) watts must exceed the startup surge of the largest motor in the house, not just the running total.
  • Dual-fuel models running on propane output approximately 5% fewer watts than on gasoline — factor that in when sizing.

Important Exceptions

  • Electric heat or electric range: Standard 7,500–12,500W sizing does not apply — a single electric range draws 5,000–8,000W running, which can max out even a DuroStar DS13000MX before you've added any other load.
  • Well pump larger than 1 HP: A 1.5 HP well pump surges to roughly 4,500–5,500W at startup; add a central AC compressor surge on the same generator and the combined peak can exceed what a 10,500W-class unit can handle safely.
  • Propane as primary fuel: The 7,500–12,500W sizing range assumes gasoline output; on propane, a DuroStar DS13000MX produces 9,975W running — size up one tier if propane will be your main fuel during an extended outage.
  • Sensitive electronics (CPAP, home office equipment): Open-frame DuroStar generators produce THD of roughly 12% or higher — too high for direct use with medical devices or laptops; run those loads through a UPS or inverter, regardless of generator wattage.
  • Multi-zone or 4-ton-plus central AC: A 4-ton system can draw 4,000–5,000W running and surge well past 7,000W; at that load, the 10,500W running watt class becomes marginal and a transfer switch wired to power only essential circuits is the safer approach.

How to Choose

  • Pick the DuroStar DS4000S (3,300 running watts) if: you only need to run a window AC unit, a refrigerator, and basic lighting — no central AC or well pump.
  • Pick a 7,500W-class DuroStar model if: your home has a smaller single-zone central AC (2-ton or under), one refrigerator, and modest lighting — and you're not running a well pump simultaneously.
  • Pick the DuroStar DS13000MX (10,500 running watts) if: your load includes a 3-ton central AC, a well pump, a full-size refrigerator, and multiple outlets running at the same time.
  • Pick a dual-fuel DuroStar model if: you're in a hurricane corridor where gas stations sell out after a storm and you keep a 40-lb propane tank on hand — size up to offset the 5% propane output reduction.
  • Pick a tri-fuel DuroStar DS13000MXT if: your home already has a natural gas line and you want the option to run indefinitely without hauling fuel during a multi-day outage.