Generac GP15500EFI (7705)
The biggest portable in this catalog — a fuel-injected 816cc engine built to feed a whole panel.
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Specs
| Running watts | 15,500 W |
| Starting watts | 19,300 W |
| Type | Open frame |
| Fuel | Gasoline |
| Weight | 420 lb |
| Fuel tank | 14.2 gal |
| Runtime (mfr claim) | ~11 h at 50% load |
| Outlets | Four 20A 125V GFCI, L14-30R (transfer switch), 14-50R (240V/50A), L5-30R |
| Start | Electric |
| CO safety shutoff | Yes — built-in CO sensor |
| Typical street price | ~$4,219 (as of July 2026 — check listing for current price) |
Figures are the manufacturer's published specs; dashes mean the maker doesn't publish a number. Verify against the current datasheet before you buy.
What can it actually run?
Checked with the same math as our calculator: total running watts, plus the single largest motor surge on top. “Tight” means it technically fits but the load sits above 80% of rated output — fine briefly, not where you want to live.
- ✓ runs itFridge, Wi-Fi, and lights730 W running · 2,230 W peak
- ✓ runs itStorm essentials (fridge, freezer, furnace fan, sump pump)3,080 W running · 4,630 W peak
- ✓ runs itEssentials plus a 10,000 BTU window AC4,280 W running · 6,680 W peak
- ✗ too muchMost of the house (well pump, central AC, laundry)13,680 W running · 19,680 W peak
The installer's take
15,500W running (19,300W surge) is standby-generator territory in a wheeled, non-permanent box — Homelink transfer-switch compatible, so paired with a manual switch this can carry a well pump, central AC, and the rest of the house at once, not just the essentials list the smaller portables handle. The 14.2-gallon tank and 11-hour runtime at half load mean fewer 2 a.m. refuels during a multi-day outage. At 420 lb it's not something two people lift into a truck bed; this lives on its wheels, parked where it'll run for days.
Pros
- 15,500W running / 19,300W surge — enough for most of a house through a transfer switch
- 14.2-gallon tank with an 816cc EFI engine for long, efficient runs
- COsense CO shutoff and low-oil shutdown built in
Cons
- 420 lb — wheeled placement only, not something you lift
- Priced and sized closer to an installed standby unit than a grab-and-go portable