A power outage that lasts hours is an inconvenience. One that lasts days — after a severe storm, grid failure, or natural disaster — can become dangerous, particularly for households that depend on medical equipment, have young children, or live in extreme climates. A home backup generator gives you control when the grid fails, but choosing the right type and size requires understanding your options.
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⚡ Key Takeaways
- There are two main categories of home backup generators, and the right choice depends on your budget, power needs, and how quickly you need backup power to kick in.
- Undersizing a generator is one of the most common mistakes homeowners make.
- Never connect a generator directly to a home outlet (a practice called backfeeding).
Types of Home Backup Generators
There are two main categories of home backup generators, and the right choice depends on your budget, power needs, and how quickly you need backup power to kick in.
Portable Generators
Portable generators run on gasoline, propane, or dual-fuel and must be started manually when an outage occurs. They range from small 2,000-watt units that can power a few essentials to large 10,000-watt models that can handle most of a home’s load. Portable generators must be operated outdoors due to carbon monoxide risk — the U.S. Consumer Product Safety Commission (CPSC) warns that generator CO poisoning kills hundreds of Americans annually — and require a transfer switch or interlock kit to safely connect to your home’s wiring. They’re the more affordable option but require manual operation and fuel management.
Standby Generators
Standby generators are permanently installed units that run on natural gas or propane and start automatically within seconds of detecting a power outage. They can be sized to power part or all of your home and require professional installation including a dedicated transfer switch. While significantly more expensive than portable generators, standby units offer hands-free operation, unlimited runtime (connected to natural gas), and protection even when you’re away from home.
How to Choose the Right Generator Size
Undersizing a generator is one of the most common mistakes homeowners make. Running a generator beyond its capacity damages the generator and may damage connected appliances.
Calculate Your Load
List the appliances and systems you want to power during an outage and their wattage requirements. Essential loads typically include refrigerator (150–400W running, up to 1,200W starting), sump pump (750–1,500W), window AC or central HVAC (up to 3,500W+ starting), lights (50–200W per circuit), and phone and device charging (50–200W). Add up the running watts and identify the highest starting watt demand — generators must handle the momentary spike when motors start.
Whole-Home vs. Essential Circuits
Whole-home generators need to match your home’s full electrical load. Essential circuit generators can be smaller and less expensive — they power only selected circuits (refrigerator, sump pump, a few lights and outlets, HVAC) via a transfer switch. For most homeowners, an essential-circuit approach with a mid-sized generator offers the best balance of capability and cost.
Choosing the right generator is step one. Our installation team can help you select and professionally install the best option for your home’s power needs.
Transfer Switch: The Critical Safety Component
Never connect a generator directly to a home outlet (a practice called backfeeding). Backfeeding sends power back through the utility lines, which can electrocute utility workers restoring power and damage your generator when power returns. A proper transfer switch or generator interlock kit is essential for safely connecting any generator to your home wiring.
Automatic Transfer Switches
Used with standby generators, automatic transfer switches (ATS) detect a power outage and switch the home from utility to generator power within seconds — without any human intervention. They also switch back automatically when utility power returns and are a required part of any standby generator installation.
Manual Transfer Switches and Interlocks
For portable generators, a manual transfer switch or interlock kit allows you to safely connect the generator to selected home circuits. These must be installed by a licensed electrician and require you to physically start the generator and flip the transfer switch during an outage.
Fuel Considerations
Fuel availability during extended outages is a key practical consideration. Gasoline can be difficult to obtain after major storms when gas stations are also without power. Propane stored in tanks provides reliable fuel reserves. Natural gas (for standby generators) is typically unaffected by outages and provides unlimited runtime, making it the preferred fuel for standby installations.
Frequently Asked Questions
How much does a home backup generator cost?
Portable generators range from $500 to $3,000 depending on size and features. Standby generators range from $5,000 to $20,000+ installed, depending on size, fuel type, and installation complexity. The installed cost includes the generator unit, transfer switch, electrical work, gas line connection, and permits.
Do I need a permit to install a home generator?
Yes. Generator installations require electrical permits in virtually every jurisdiction. A licensed electrician handles the permit application and ensures the transfer switch installation meets code. Unpermitted generator installations can create problems with your homeowner’s insurance and utility provider.
How big a generator do I need for my house?
Most homes can cover essential circuits with a 7,500–12,000 watt generator. Whole-home coverage for average homes typically requires 14,000–20,000 watts. A licensed electrician can perform a load calculation to determine the right size for your home and priorities.
Can I run my central air conditioning on a generator?
Central AC is one of the highest-demand loads in a home. Running central AC requires a generator sized specifically for that load — typically 14,000 watts or more to handle the starting surge. Many homeowners choose to prioritize other essentials over central AC during outages, or use a window unit on a smaller generator.
How often should I service my standby generator?
Standby generators should be serviced annually, including oil change, filter replacement, spark plug check, and battery test. Most modern standby generators run a brief weekly self-test cycle automatically. Your electrician or generator installer can set up a maintenance contract to handle annual service.