Yes, a properly set up generator will work when the power grid goes out. That is exactly what backup generators are designed to do: they produce electricity independently of the grid, using their own fuel source. But “properly set up” is the key phrase. How well your generator serves you during an outage depends on the type you have, how it connects to your home, and whether you’ve sized it correctly for the appliances you need to run.
How Generators Work Independently of the Grid
A generator burns fuel (gasoline, propane, natural gas, or diesel) to spin an engine that produces electricity. This process has nothing to do with the power grid. The grid could be down for days or weeks, and your generator will keep running as long as it has fuel and is mechanically sound.
The confusion some people have is whether a generator needs grid power to “start” or function. It doesn’t. Portable generators start with a pull cord or electric ignition powered by their own battery. Standby generators (the permanent units installed outside your home) use a small onboard battery to start automatically. Neither type depends on the grid to operate.
Standby vs. Portable: What Changes During an Outage
The experience of losing power feels very different depending on which type of generator you own.
A permanent standby generator detects the outage for you. Its automatic transfer switch monitors the voltage and frequency coming from the grid, and when it senses a disruption, it signals the generator to start, waits for the engine to reach steady operation, verifies the output is stable, and then connects your home’s electrical panel to generator power. This entire process typically takes 10 to 30 seconds. You might notice the lights flicker off and back on, but you won’t need to do anything.
A portable generator requires you to act. You’ll need to wheel it out, position it safely, connect it to your home or appliances, and start it manually. Smaller portable units power individual appliances through extension cords plugged directly into outlets on the generator. Larger portables can connect to your home’s electrical panel through a transfer switch, which lets you power hardwired systems like well pumps, water heaters, and your furnace. Without a transfer switch, you’re limited to whatever you can plug in with extension cords.
Why You Need a Transfer Switch or Interlock
If you want to power your home’s wiring (not just a few appliances via extension cords), you need a safe way to disconnect from the grid before connecting your generator. This is not optional. Plugging a generator directly into a household outlet or wiring it into your panel without a proper disconnect creates a condition called backfeed, where electricity from your generator flows backward through your electrical panel and out into the neighborhood power lines.
Backfeed is potentially fatal. Utility workers repairing downed lines assume those lines are dead. A backfeeding generator can energize an entire stretch of distribution wiring, creating an electrocution hazard for repair crews and neighbors served by the same transformer. Connecting a generator directly to household wiring without a transfer switch violates electrical codes everywhere in the United States.
You have two main options for safe connection:
- Transfer switch: A dedicated device wired into your electrical panel that physically prevents the grid and the generator from being connected at the same time. Manual versions require you to flip the switch yourself. Automatic versions (standard on standby generators) detect the outage and switch over without any input from you. Transfer switches cost more and require professional installation with dedicated circuits.
- Interlock kit: A simple mechanical plate installed on your existing breaker panel. It works as a sliding barrier that prevents the main utility breaker and the generator breaker from being turned on simultaneously. Interlocks are less expensive and simpler to install, but they’re entirely manual. You slide the plate, turn off the main breaker, then turn on the generator breaker.
Sizing Your Generator for the Right Appliances
One of the most common mistakes is buying a generator that can’t handle the appliances you actually need during an outage. The issue isn’t just how much power an appliance uses while running. Motors in devices like well pumps, sump pumps, and air conditioners draw dramatically more power at the moment they start up, sometimes three to seven times their normal running wattage.
Here’s what that looks like in practice. A half-horsepower well pump runs on about 1,000 watts, but it needs 2,100 to 4,000 watts just to start. A sump pump of the same size runs at roughly 1,050 watts but can spike to 4,100 watts on startup. A window air conditioner rated at 7,000 to 10,000 BTU runs on 1,000 to 1,500 watts, yet starting it demands 2,200 to 5,000 watts.
To size a generator correctly, add up the running wattage of everything you want to power simultaneously, then make sure the generator’s surge (or starting) wattage rating can handle the largest motor you’ll need to start. If your generator’s surge capacity is too low, the motor won’t start, or it could trip the generator’s overload protection and shut everything off. Most people prioritize their refrigerator, a few lights, a well pump if they’re on well water, and heating or cooling depending on the season.
Fuel Supply During Extended Outages
Your generator only works as long as it has fuel, and fuel availability can become a real problem during prolonged outages. Each fuel type has different vulnerabilities.
Gasoline is the most common fuel for portable generators, but gas stations need electricity to pump fuel. During widespread outages, stations may be closed. Stored gasoline degrades over time as well. Untreated gasoline starts to break down after a few months, but adding a fuel stabilizer keeps it usable for up to two years when stored in proper containers. If you rely on a gasoline generator, keeping 10 to 20 gallons of stabilized fuel on hand gives you a meaningful buffer.
Natural gas is piped directly to standby generators, which seems like an advantage since you never need to refuel. In most outages, natural gas pipelines remain pressurized because they operate independently of the electrical grid. However, during extreme events, this isn’t guaranteed. During the 2021 Texas winter storm, some pipeline compressor stations that ran on grid electricity shut down when rolling blackouts hit, dropping gas pressure across the regional system. Pipeline operators can also shed residential load during high-stress events to maintain system stability. Natural gas is reliable for typical outages but not immune to failure during the kind of catastrophic grid event where you need a generator most.
Propane, stored in a tank on your property, avoids both problems. It doesn’t degrade over time and doesn’t depend on any external delivery infrastructure during the outage itself. The tradeoff is that your tank holds a finite amount, and refilling requires a delivery truck that may not be running during a major event.
Keeping Your Generator Ready
A generator that sits unused for months may not start when you need it. Engines that haven’t run develop stale fuel, dead batteries, and corroded connections. Standby generators address this with automatic self-test cycles, typically running under load for about 30 minutes once a month. The industry recommendation is to test at 30% to 50% of maximum load capacity monthly. If a monthly test reveals a problem, the generator should be run for at least two consecutive hours after repairs to confirm reliability.
For portable generators, the maintenance falls on you. Run the engine for 15 to 30 minutes every month or two, use stabilized fuel if the generator will sit idle between uses, and check the oil level and air filter before storm season. The worst time to discover a dead battery or clogged carburetor is during a blackout.
Placement and Carbon Monoxide Safety
Portable generators produce carbon monoxide, an odorless gas that kills hundreds of people in the United States every year during storm-related outages. Place your portable generator outdoors, at least 20 feet from any doors, windows, or vents. Never run one in a garage, even with the door open. Carbon monoxide accumulates faster than most people expect, and symptoms (dizziness, confusion) can make it hard to recognize the danger before it’s too late. Many newer portable generators include automatic carbon monoxide shutoff sensors, which is a feature worth prioritizing if you’re buying new.
Standby generators are permanently installed outdoors by a professional, so carbon monoxide placement is handled during installation. Local codes typically specify minimum distances from windows, property lines, and gas meters. Most jurisdictions require a permit for installation, and the review process for electrical plans can take five or more business days, so this isn’t something to arrange the week before a hurricane.