Free Guide to Home Backup Generators

Understanding How Home Backup Generators Work

A home backup generator is a machine that produces electricity when your main power supply fails. Generators work by converting mechanical energy into electrical energy through an internal combustion engine or other power source. When your utility power goes out, the generator automatically detects the outage and turns on, supplying electricity to your home until power is restored.

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Most residential backup generators use either natural gas, propane, or diesel fuel to operate. Natural gas generators connect directly to your home's existing gas line, making them convenient for long-term use since fuel doesn't need to be stored on your property. Propane generators store fuel in a tank on your property and can operate independently of utility lines. Diesel generators are less common for residential use but offer good fuel efficiency for those who already have diesel storage.

Generators come in different sizes, measured in kilowatts (kW). A typical home uses between 5 kW and 20 kW during normal operation, but backup generators are usually sized to power essential systems only—such as your heating system, refrigerator, water heater, and lights. A 7-10 kW generator can handle most essential household systems, while larger homes or those with more appliances may need 15-20 kW or more.

The generator connects to your home's electrical system through a transfer switch, which is a safety device that prevents backfeeding electricity into utility lines when the generator is running. This protects utility workers from electrical hazards. When utility power returns, the transfer switch automatically switches back to the main power supply.

Practical Takeaway: Before shopping for a generator, list which appliances and systems you consider essential during an outage—typically heating, refrigeration, water heating, and lighting. This helps determine the right size for your needs and budget.

Types of Backup Generators for Residential Use

Standby generators are permanently installed outside your home, usually in a concrete pad near your house. These units automatically start when they detect a power outage and run until utility power is restored. Standby generators are the most popular choice for whole-home backup because they require no manual intervention and can run for extended periods. They're typically powered by natural gas or propane and are quieter than portable alternatives because they're installed away from living spaces.

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Portable generators are smaller, movable units that you can store in a garage or shed and wheel out during an outage. These typically range from 3 kW to 10 kW and run on gasoline or propane. Portable generators cost significantly less than standby units—often between $500 and $3,000—but require manual setup, fuel management, and produce more noise. They're suitable for powering essential appliances during an outage but not for whole-home backup.

Battery backup systems, sometimes called home battery storage or uninterruptible power supplies (UPS), store electrical energy and release it during outages. These systems are often paired with solar panels to recharge during the day. Battery systems provide quiet operation with no fuel needed, but they have limited runtime and typically cost more upfront than traditional generators. They work well for short outages or to bridge the time until a backup generator starts.

Inverter generators are portable units that produce cleaner electrical power, making them safer for sensitive electronics like computers and phones. They adjust engine speed based on power demand, using less fuel and producing less noise than standard portable generators. Inverter generators cost more than conventional portable models but are increasingly popular for residential backup.

Hybrid systems combine battery storage with a traditional generator. During a short outage, the battery provides power immediately while the generator starts up. This approach reduces fuel consumption and wear on the generator engine, extending its lifespan.

Practical Takeaway: Consider your budget, installation space, and how long you typically need backup power. Standby generators offer convenience and whole-home coverage but cost $3,000-$15,000 installed. Portable generators are cheaper but require more work during an outage.

Sizing Your Generator for Your Home's Needs

Calculating the correct generator size involves determining the wattage of appliances you want to run during an outage. Every electrical device has a power requirement measured in watts. You can find this information on the appliance's label or in its manual. Start by listing essential items: HVAC system, water heater, refrigerator, freezer, lighting, and perhaps a sump pump or well pump if you have one.

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Different appliances have different power requirements. A refrigerator typically uses 600-800 watts while running, but may surge to 2,200 watts when the compressor first starts. Many devices draw more power during startup than during normal operation—this is called inrush current or surge power. Your generator must handle both the running watts and the starting watts of all devices you might run simultaneously.

To calculate your needs, add up the running watts for all appliances you plan to use at the same time. For example: central air conditioning (3,500 watts) plus water heater (4,500 watts) plus refrigerator (800 watts) plus lighting (1,000 watts) equals 9,800 watts. You'd want a generator rated for at least 10 kW to handle this load. However, most people don't run their air conditioning and water heater simultaneously during an outage, so realistic needs are often lower.

A general sizing guideline: homes under 3,000 square feet typically need 5-10 kW generators, while larger homes may need 15-20 kW. If you want to power everything in your home simultaneously—called whole-home backup—you may need 20-30 kW or larger. Most homeowners choose generators that power essential systems only, reducing size and cost.

Online generator sizing calculators are available from manufacturers and retailers. You input your appliances and their wattages, and the tool calculates the recommended generator size. This approach is more accurate than estimating.

Practical Takeaway: Make a list of what you truly need to power during an outage, find the wattage for each item, add them up (including surge power), and choose a generator rated slightly above that total. Oversizing is wasteful and expensive, while undersizing means unpowered appliances during an outage.

Installation, Maintenance, and Safety Considerations

Installing a standby generator requires professional work in most cases and should follow local building codes. The installation process includes placing the generator on a concrete pad, running fuel lines from your gas supply or propane tank, installing the transfer switch inside your home's electrical panel, and running electrical conduit from the generator to your home. This typically costs $2,000-$5,000 in labor alone. You'll need to obtain permits and pass inspections before the system can operate legally.

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Proper placement is important for safety and function. Generators should be positioned at least 5 feet away from windows, doors, and air intakes to prevent carbon monoxide (CO) from entering your home. The exhaust should point away from your house. Generators need adequate ventilation, protection from weather, and access for maintenance. They should be on level ground to ensure proper oil circulation.

Regular maintenance keeps your generator reliable. Monthly, check the oil level and condition—generators typically require oil changes every 50-100 hours of operation or annually, whichever comes first. Test run your generator monthly for 10-15 minutes under no load to keep internal parts lubricated and fuel systems clean. For natural gas generators, have a professional inspection annually. For propane generators, inspect propane lines and connections for leaks using soapy water—bubbles indicate a leak that needs repair.

Battery-powered transfer switches and automatic shutoffs should be tested regularly. Many homeowners hire a service technician to perform annual maintenance, typically costing $150-$300. This ensures the generator will start when needed and operates safely.

Safety warnings include never running a generator indoors, in a garage, basement, or crawlspace—generators produce carbon monoxide, an odorless gas that can be fatal. Never refuel a generator while it's running or hot. Keep a fire extinguisher nearby. Ensure proper grounding to prevent electrical hazards. Don't overload the generator by plugging in more than its rated capacity.

Practical Takeaway: Budget for professional installation and annual maintenance of standby generators. Plan for 15-30 minutes of monthly upkeep tasks. Never ignore safety