Choose a Home Backup Generator by What Must Stay On

Choose essential loads first, then decide whether you need manual or automatic backup. A portable generator can be practical when someone can safely set it up and manage fuel. A permanently installed standby system is worth considering when power must return while you are away.

Before buying a portable, confirm that you have a safe operating location: outdoors, at least 20 feet from the house and from windows, doors or vents, with exhaust pointed away from any building someone could enter. Never run it in a garage, shed, porch or carport. Open doors do not make enclosed operation safe. See CDC guidance and CPSC safety guidance.

Portable or standby?

Your requirement	Option to investigate	Main condition
Keep a refrigerator, lights and communications working	Portable generator	Safe outdoor placement, suitable cords and someone to operate it
Supply selected hardwired circuits, such as a furnace or pump	Portable generator with professionally installed transfer equipment	Generator voltage, starting capacity and connection must match the loads
Restore selected circuits automatically, including while away	Standby generator with automatic transfer	Suitable installation site, fuel supply and local approvals
No safe outdoor location for a fuel-burning portable	Battery backup instead	Check usable energy, starting surge and recharging options

Generac’s residential standby systems, for example, start automatically after detecting an outage, operate on natural gas or propane, and shut off after utility power returns. That does not mean every standby generator can power every household appliance simultaneously. Generac’s standby FAQ describes operation and the need for sizing.

If placement rules rule out a portable, use our home battery backup guide rather than trying to make a balcony or garage work.

Size the loads—not the house’s floor area

Make a list of what must remain powered: refrigeration, sump or well pump, furnace equipment, medical equipment, lights and communications. Keep optional loads separate.

For each essential appliance, record:

• Running watts: power required during operation.
• Starting watts: the brief demand when a motor or compressor starts.
• Voltage and connection: including whether it needs 240 volts or is hardwired.

Use the appliance manual or manufacturer’s data. Generic wattage tables are estimates; Honda’s wattage guide labels its figures approximate and distinguishes running demand from starting demand.

For a first-pass calculation when only one motor starts at a time:

Running requirement = sum of loads operating together

Starting requirement = running total + largest additional starting demand

“Additional” means that motor’s starting watts minus its running watts—you have already counted its running load.

For example, suppose your running total is 1,800 watts, and the largest motor needs 800 watts running but 2,400 watts to start:

1,800 + (2,400 − 800) = 3,400 watts during startup.

That is a hypothetical example, not a recommended size for every home. Compare the result with both the generator’s continuous rating and its permitted surge output and duration. If pumps or compressors can restart together, have the installer account for that overlap rather than relying on the one-motor assumption. Honda explains how staggering loads can reduce required capacity in its power-management guide.

Do not mistake the model’s headline wattage for continuous output. One manufacturer example—the Honda EU7000iS—is listed at 7,000 watts maximum but 5,500 watts rated output in its specifications, checked October 5, 2026.

Plan the connection before purchasing

There are two distinct jobs: powering plug-in appliances and supplying the home’s wiring.

For plug-in loads, use appropriately rated outdoor extension cords and follow the generator manual. For building wiring, arrange a qualified electrician and properly installed transfer equipment. Never plug generator output into a household receptacle to energize the house. An improper connection can energize utility wiring and electrocute workers or others. OSHA’s generator safety sheet

Ask the electrician to verify generator voltage, inlet and cord ratings, transfer compatibility, grounding and neutral configuration. For automatic backup, see our automatic transfer switch selection guide.

A whole-home transfer connection is not a promise of unlimited power. Tell the installer which loads must run together and which can be switched off or managed.

Plan for rain without moving a portable indoors. Follow the model’s electrical-shock precautions for wet weather; CPSC notes that instructions may allow a suitable noncombustible generator tent or require waiting until rain passes. CPSC wet-weather guidance

Runtime depends on load, fuel and maintenance

Compare runtime claims at the same load, not just “hours per tank.” Honda lists the EU7000iS’s 5.1-gallon tank at 16 hours at quarter load versus 6.4 hours at rated load. Those are manufacturer figures for that model, not guaranteed outage runtime or a universal reduction percentage. Runtime specifications, checked October 5, 2026.

Before choosing fuel, answer three questions:

1. How long must essential loads operate before you can replenish fuel?
2. Where can fuel be stored safely and legally?
3. What happens if the planned fuel supply is unavailable?

Automatic operation is not maintenance-free operation. Arrange someone to perform the checks and shutdowns required by the exact manual during a long outage. For example, Generac requires shutdown and inspection after every 24 hours of continuous operation for the air-cooled standby generators covered by its extended-runtime guidance.

Shut a portable generator down and let it cool before refueling. Keep fuel away from living areas and ignition sources. OSHA refueling and storage precautions

What to include in an installation quote

For standby backup, request an itemized quote covering the generator, transfer equipment, site preparation, fuel connection, permits and commissioning—not just the generator itself. Confirm model-specific placement clearances and property restrictions; the portable 20-foot rule is not a standby installation specification.

Generac’s installation guidance describes site and fuel planning, permitting, and a simulated outage before completion.

Before the first outage, test the planned loads and transfer procedure. Install battery-powered or battery-backup CO alarms on every level and outside sleeping areas, and test them monthly. If a CO alarm sounds, get everyone outside immediately, then call 911. A generator’s CO shutoff feature does not replace safe placement or home alarms. CPSC generator and alarm guidance