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The Generac 5500 generator, sold as the GP5500, is one of the most common mid-size portable units in the country. The reason is simple: 5,500 running watts covers the realistic backup list for most homes at a fraction of what a standby install costs. Fridge, freezer, a window AC or a space heater, lights, the router, phone chargers - all at once. Central air is off the table. Whether that trade works for you depends on what your outage actually looks like, so let's go through it.
What the Generac 5500 actually runs
The headline numbers are 5,500 running watts and 6,875 starting watts. Running watts is what the machine holds all day; starting watts is the short burst motors need when they kick on. That burst is why a fridge that draws 800 running watts might demand 2,000 for a second at startup, and why the surge number matters as much as the running number when you're building a load list.
Here's a realistic combo that fits with room to spare:
- Refrigerator: 700-1,000 running watts, triple that at startup
- Chest freezer: 500-800 running watts
- Window AC (10,000 BTU): 900-1,200 running watts
- Furnace blower: 800 or so
- Lights, router, modem, phone chargers: under 300 combined
That stack sits around 3,500 running watts, roughly 64% of load, which also keeps runtime long and the noise predictable. What the Generac 5500 can't carry: central air (most systems need more starting surge than 6,875 provides), an electric water heater (4,500 watts by itself), an electric dryer, or an electric range. Those are the loads that push people to a standby unit, and the standby vs portable breakdown walks through that decision honestly.
If you're shopping at this wattage, check the current GP5500 price on Amazon - it moves with the season.
GP5500 specs that matter
The spec sheet is short, which is part of the appeal:
| Spec | Value |
|---|---|
| Running watts | 5,500 |
| Starting watts | 6,875 |
| Engine | 389cc OHV, pull start |
| Fuel tank | 7.2 gallons, steel |
| Outlets | Two 120V household (5-20R), one 120/240V 30A twist-lock (L14-30R) |
| Weight | Just over 180 pounds, never-flat wheels |
| Hour meter | Yes |
That twist-lock outlet is the one to pay attention to. It's what you plug a transfer switch inlet box into, which means you can backfeed your house circuits safely instead of running extension cords through a window. If you've never wired one up, the transfer switch explainer covers how the connection works and why you want an electrician involved.
Runtime and fuel use on the 7.2-gallon tank
Generac rates the GP5500 at up to 10 hours at 50% load on a full tank. That works out to roughly 0.7 gallons an hour at half load. In practice, overnight loads run lighter than the rating assumes - the fridge cycles on and off, lights are LED, nothing else runs at 2 a.m. - so a tank filled before bed often stretches past the rated figure.
Two practical notes. First, fill the tank before the storm, not during; gas stations lose power in exactly the same outages you're preparing for. Second, how long you'll actually need to run matters by region - the power outages by state data shows some parts of the country average under two hours a year per customer, where others stretch into days. A 10-hour tank is plenty for the first group and a starting point for the second.
GP5500 vs GP6500: when stepping up is worth it
The GP6500 uses the same 389cc engine and the same 7.2-gallon tank, but delivers 6,500 running watts and 8,125 starting watts. The extra 1,000 running watts buys headroom: a second window AC, a well pump with a hard start, or simply less load management when everyone's home.
The rule of thumb: if your must-run list adds up under 4,000 running watts, the GP5500 is the right size. If you're already negotiating with yourself about which appliance to unplug, take the GP6500 on Amazon instead - the price gap is usually a hundred dollars or so, and running a generator at 90% load all day is no fun for the engine or your ears.
Where the 5500 falls short
No review is complete without the honest list. The GP5500 is an open-frame machine, which means it's loud - this is a "runs out in the garage with the door open" generator, not a quiet camping unit. It's pull-start only, and yanking a cold 389cc engine to life at 6 a.m. in January is a real workout; the electric-start versions sit one tier up in Generac's lineup. And it's not an inverter, so power is fine for fridges, pumps, and power tools but you should keep laptops and sensitive electronics on surge protectors, or run them off a small inverter generator instead.
For a fuller picture of how this unit stacks against other brands, the generator comparison page lays out the field.
FAQ
How long will a Generac 5500 run on a tank of gas?
Up to 10 hours at 50% load per Generac's rating, on the 7.2-gallon tank. Lighter overnight loads often stretch that to 12 or more.
Will a GP5500 run central air?
Usually not. Most central AC systems need more starting surge than the 6,875 watts available, and you'd need a transfer switch anyway. Window units are the realistic cooling play at this wattage.
How much does a Generac 5500 generator cost?
Typically somewhere between $700 and $850 depending on seller and season, with sales clustering around storm season. Prices move, so check current listings before you plan a budget around a number.
What size generator do I actually need?
Add up the running watts of everything on your must-run list, then add the startup surplus of the biggest motor in the group. The generator size calculator does the math in two minutes.
The bottom line
The Generac 5500 generator earns its popularity the boring way: enough watts for the outage list that actually matters, a transfer-switch-ready outlet, a tank sized for overnight runs, and a price in the mid-hundreds instead of five figures. Keep your must-run list under about 4,000 running watts and it's the right machine. Creep past that, and the GP6500 is the smarter spend. Either way, size the load first and check how long outages really last where you live - those two numbers decide everything else.
