The first power outage after you buy a house feels different than the ones you sat through as a renter. Now it’s your fridge full of food, your sump pit filling up, your kids asking why the internet died. I spent twelve years wiring and servicing backup power for folks in exactly that spot, and the questions were always the same.
A portable generator is usually where beginners start, and honestly, it’s a smart place to start. It’s a few hundred to a couple thousand dollars instead of five figures, you can buy one this weekend, and it’ll cover the stuff that actually matters during a storm.
What trips people up isn’t the machine. It’s the details nobody explains at the big-box store. So let’s walk through it the way I would if we were standing in your driveway.
Key takeaways
- A 3,500 to 7,500 watt portable unit covers most homes’ essentials during an outage.
- Add up the running watts of what you actually need first, then buy for headroom.
- Never run a generator in a garage or near windows. Carbon monoxide kills fast and silent.
- A transfer switch or interlock is the safe, legal way to power your house circuits.
What a portable generator for home backup actually does
Think of a portable generator as a small gasoline engine spinning an alternator. It makes electricity while it runs, and it runs as long as you keep feeding it fuel. That’s the whole trick.
Most of these units put out somewhere between 2,000 and 8,000 running watts. That’s enough to keep a fridge cold, run a few lights, charge phones, and maybe run a furnace blower or a well pump, one or two at a time. It is not enough to run your whole house like nothing happened, and anyone selling you that idea is stretching the truth.
If you want the lights-never-flicker experience, that’s a different animal, and I cover it in the whole-house standby generator guide. For most beginners, though, portable is the right call for a first machine.
Figure out your wattage before you shop
Here’s the mistake I see all the time: someone buys the biggest generator on the shelf “to be safe,” burns twice the fuel they need, and still trips it because they plugged in a well pump wrong. Size comes from math, not from the price tag.
Every appliance has two numbers. Running watts is what it draws while it hums along. Starting watts is the surge when the motor kicks on, and for anything with a compressor or pump it can be two to three times the running figure.
A quick example load
| Appliance | Running watts | Starting watts |
|---|---|---|
| Refrigerator | 700 | 2,200 |
| Sump pump (1/3 hp) | 800 | 2,000 |
| Furnace blower | 600 | 1,800 |
| Lights + phones | 300 | 300 |
| Microwave | 1,000 | 1,000 |
Add the running watts and you’re around 3,400. But you never start everything at once, so plan for the single largest starting surge on top of your steady load. In this case a solid 5,000 to 6,000 watt unit handles it with room to spare.
If you want to walk through this properly for your own house, I broke down the full method in how much wattage a portable generator needs. Do the exercise once and you’ll never guess again.
Buy about 20 percent more capacity than your math says. A generator loafing at 60 to 70 percent of its rating runs quieter, sips less fuel, and lasts longer than one pinned at redline every storm.
Fuel: what you’ll be feeding it
Most starter units run on regular gasoline, and gas is fine until it isn’t. It goes stale in about a month, so the can you stored last spring may not fire your engine in December. I always tell people to add stabilizer and rotate their fuel.
Propane is the other common option. It stores for years, burns cleaner, and doesn’t gum up a carburetor, though you’ll get a little less power out of the same engine. A dual-fuel unit lets you switch between the two, which is genuinely handy when gas stations are dark after a big storm.
I explain how those switch-ready machines work in this breakdown of dual-fuel portable generators, and if you’re still torn on gas versus propane versus diesel, the fuel types comparison lays it out side by side.
Getting power into your house without killing anyone
You’ve got two honest ways to use a portable generator. Running extension cords straight to appliances is the cheap route, and for a fridge and a couple lamps it works fine.
The better way is a transfer switch or a panel interlock, installed by a licensed electrician. That lets you power actual house circuits, your furnace, your well pump, your kitchen outlets, from one cord plugged into an inlet on the wall.
Never “backfeed” by plugging a generator into a wall outlet with a double-male cord. It can send live power back onto the utility line and electrocute a lineman working to restore your service. It’s illegal, and I’ve seen it start a house fire. Use a transfer switch, period.
Placement matters just as much. Carbon monoxide from a running generator has killed people who put it in an attached garage with the door open. Keep it outside, at least 20 feet from the house, pointed away from windows and doors. The CPSC has clear guidance on this at cpsc.gov, and Ready.gov’s outage page at ready.gov is worth a read before storm season.
A first-timer’s setup checklist
Before the next outage catches you flat-footed, run through this once. It takes an afternoon and saves you a miserable night in the dark.
- Add up your running watts and identify your biggest starting surge.
- Buy a unit with roughly 20 percent headroom over that number.
- Store 5 to 10 gallons of fresh, stabilized fuel (or a spare propane tank).
- Have an electrician install a transfer switch or interlock kit.
- Buy a CO detector for the house and a heavy 10-gauge outdoor cord.
- Run the generator for 20 minutes now so you learn the starter before you need it.
For the full rundown on running one without hurting yourself or the machine, keep this safety walk-through handy. I reference it every time a customer takes delivery.
Where to go from here
If you do just one thing this week, do the wattage math for your own house. That single number tells you which generator to buy, how much fuel to keep, and whether a portable unit even fits your needs or you should be looking at standby.
On a job last winter, a couple had bought a 3,000 watt unit that couldn’t start their well pump, and they’d gone three days without running water. Twenty minutes with a calculator beforehand would have saved them the whole ordeal. Grab a notepad, walk your house, and add it up. Your future self, sitting warm during the next outage, will thank you.
