A residential generator is a machine that produces electricity when the power grid goes down. Unlike the grid, which delivers power through lines connected to your home, a generator creates electricity on-site using a fuel source. Understanding the different types available helps you figure out what might work for your situation.
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Portable generators are the smallest option. They typically weigh between 100 and 500 pounds and run on gasoline, propane, or diesel. You can move them around your property and store them in a garage or shed when not in use. A portable generator might power essential items during a blackout—a refrigerator, some lights, a water heater, or a sump pump—but not your whole house at once. Most homeowners rent or own portable units for backup during temporary outages lasting hours to a few days.
Standby generators (also called permanent or whole-house generators) are larger machines permanently installed outside your home, much like an air conditioning unit. These connect directly to your home's electrical system through an automatic transfer switch. When the power grid fails, a standby generator detects the outage and starts automatically without you doing anything. Standby generators run on natural gas or propane and can power your entire house for extended periods. They're the most expensive option but require no manual setup during an emergency.
Inverter generators are a newer technology that produces cleaner electrical power than standard portable generators. They adjust their engine speed based on the load, which means they use less fuel and run more quietly. Inverter generators work well for sensitive electronics like computers, phones, and medical equipment. They cost more than basic portable models but less than standby systems.
The fuel source matters significantly. Natural gas generators connect to your home's existing gas line, so fuel supply isn't a concern during extended outages—as long as the gas company's infrastructure remains operational. Propane generators use tanks you fill periodically; you need to monitor tank levels and have backup tanks on hand. Gasoline generators are common for portable units but require storing gasoline safely, which has a limited shelf life. Diesel generators are efficient and durable but produce more noise and emissions.
Practical takeaway: Portable generators suit temporary outages and work for people with limited budgets or space. Standby generators make sense if you live in an area with frequent extended outages and want automatic protection. Inverter generators are worth considering if you need to power electronics or want quieter operation.
Generator capacity is measured in watts. Understanding this number prevents you from buying a generator too small to do what you need or paying for more capacity than you'll use. Every appliance and device in your home requires a certain amount of watts to run. Some devices need more power to start (called starting watts) and then use less while running (called running watts).
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Air conditioners, water heaters, and refrigerators have high starting-watt requirements—sometimes two to three times their running watts. A typical refrigerator might need 600 running watts but 2,000 watts during startup. If your generator doesn't provide enough starting watts, it will shut down when that appliance turns on. This is the most common mistake people make when sizing generators.
To calculate your needs, list the devices you want to run during an outage and note their wattage. You can find this information on the device itself (usually on a sticker or label), in the manual, or by searching online. Add up the running watts for all devices you'd use simultaneously. Then add a buffer—many experts recommend adding 20-30% to your total to account for starting power and have headroom.
For a basic scenario: if you want to run a refrigerator (600 watts), three LED lights (50 watts each), a laptop (100 watts), and a water heater (3,000-4,000 watts to start), you'd need a generator rated for at least 4,500-5,000 watts. But do you really need the water heater running? If you only want hot water for a few showers, a smaller portable generator could handle the refrigerator and lights, while you let the water heater cool down during the outage.
Be realistic about simultaneous usage. You probably won't run your air conditioning, electric oven, dryer, and heater all at once during an outage—and most people prioritize differently during emergencies. Typical priority items are refrigeration, well pumps (if you have a private well), medical equipment, a few lights, and charging devices.
Some people calculate two scenarios: a "minimum" setup that keeps essentials running, and an "expanded" setup for comfort if the outage lasts longer. A minimum setup might be 3,000-5,000 watts for a small portable generator. An expanded setup might be 7,500-10,000 watts. Whole-house standby generators typically range from 10,000 to 20,000 watts.
Practical takeaway: Create a list of must-have items and their wattages, then add 25% for safety. This number guides your shopping and prevents buying equipment that's either undersized or unnecessarily expensive.
Where you put a generator matters for safety, efficiency, and lifespan. Generators produce carbon monoxide, a deadly, odorless gas. Every year, people die from running generators indoors or too close to windows and doors. The fundamental rule: never run a generator inside your home, garage, basement, crawl space, or enclosed shed. It must be outside and at least 20 feet away from windows, doors, and vents that lead into the house.
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Portable generators should sit on a level, dry surface. Concrete is ideal. The generator needs protection from rain and snow, so many people build or buy a simple canopy or shelter. Some build three-sided sheds that allow air circulation but block weather. Never cover a running generator completely because it needs ventilation to dispel heat and exhaust. Once it shuts off or cools down, a tarp or cover can protect it.
Fuel storage requires caution. Gasoline should be stored in approved metal containers, away from the home, away from ignition sources, and ideally in a shed or garage with good ventilation. Propane tanks must be stored upright and away from living areas. Never store large amounts of gasoline—buy only what you'll use in 30 days, as old gasoline breaks down and causes engine problems. Propane tanks last longer but should be checked for leaks periodically.
Standby generators need professional installation. They connect to your home's electrical panel through a transfer switch, and improper installation can damage your generator, your home's electrical system, or the utility grid. Some homeowners try DIY installation, but most local codes require licensed electricians to handle this work. The transfer switch itself typically costs $1,500-$3,000 for parts and installation, on top of the generator's purchase price.
Grounding is essential for any generator. Portable generators should have a ground rod driven into the soil, and the generator should be bonded to that rod with heavy-duty cable. Standby generators come with grounding requirements as part of their installation. Proper grounding protects you and your home if there's an electrical fault.
Before running a generator, check the oil level and make sure it has fuel. Portable generators have small oil reservoirs; running one dry damages the engine. Check the manual for specifics. Synthetic oil works well and lasts longer than conventional oil. Keep the generator well-maintained—change the oil according to the schedule, replace air filters, and if storing it long-term, treat the fuel with a stabilizer to prevent breakdown.
Practical takeaway: Place portable generators 20+ feet from your home's openings, keep fuel stored safely away from the house, and schedule professional installation for standby systems. Regular maintenance extends the life of any generator significantly.
Your generator is only as useful as the fuel available to run it. During natural disasters or widespread power outages, fuel shortages happen quickly. Gas stations shut down without power to pump fuel, propane deliveries stop, and everyone competes for limited supplies. Thinking through your fuel strategy now matters.
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Natural gas generators have a major advantage: fuel is piped directly to your home
This guide is for general information only and is not medical, financial, legal, or other professional advice. For decisions specific to your situation, consult a qualified professional. See our Editorial Policy.