Portable Generator for Home: Complete Guide

When the grid goes down, a portable generator for home use keeps your fridge cold, your furnace running, and your phones charged for a fraction of the cost of a whole-house standby unit. But buying the wrong size wastes money, and running it the wrong way kills people every winter. This guide walks you through sizing by wattage, fuel choices, how to get power safely into the house, and the carbon monoxide rules that are not optional.

Running Watts vs Starting Watts

Every generator lists two numbers, and confusing them is the most common sizing mistake. Running watts (or rated watts) is the continuous power a device draws once it is going. Starting watts (or surge watts) is the brief spike a motor pulls at the instant it kicks on, and it can be two to three times the running draw.

A refrigerator might run at 700 watts but surge to 2,200 for a second when the compressor starts. A well pump running at 1,000 watts can surge past 3,000. Your generator has to cover the total running watts of everything on at once, plus the single largest starting surge on top of that. Size to the surge, not the average, or the generator will stall and trip when the furnace fan and the fridge kick on together.

Sizing a Portable Generator for Home Backup

Add up the running watts of what you truly need, then add the biggest single starting surge. Typical draws:

• Refrigerator/freezer: 700 running / 2,200 starting
• Gas furnace blower: 800 running / 2,300 starting
• Well pump (1/2 HP): 1,000 running / 3,000 starting
• Sump pump: 800 running / 1,300 starting
• Window AC (10,000 BTU): 1,200 running / 3,600 starting
• Lights, phones, TV, WiFi: 400 to 600 running combined
• Microwave: 1,000 running

For most homes, a 5,000 to 7,500 running-watt generator covers the essentials: fridge, furnace, well or sump pump, lights, and small electronics with room for one surge. Step up to 9,000 to 10,000 watts if you want to add central air or an electric water heater. Going bigger than you need just burns more fuel at idle, so match the unit to a realistic essentials list.

Fuel Types: Gas, Propane, Dual Fuel

The three common fuels each have trade-offs:

• Gasoline: highest power output and easy to find, but it goes stale in 3 to 6 months without stabilizer, and you cannot safely store large amounts. A 7,500-watt unit burns roughly 0.75 gallons per hour at half load, so a full 6.6-gallon tank runs about 8 to 10 hours.
• Propane: stores indefinitely in sealed tanks, burns cleaner, and starts well in cold weather. It delivers slightly less peak power than gas and a 20-lb tank runs a mid-size unit about 5 hours at half load.
• Dual fuel: runs on either gas or propane, which is the smart default. You get gasoline’s power when you need it and propane’s long shelf life for storage between outages.

For occasional outage backup, dual fuel with a couple of 20-lb propane tanks on hand is hard to beat. You are never stuck with stale fuel and can top off with gas when the storm is coming.

Getting Power Into the House Safely

You have three legitimate ways to use the power, from simplest to best:

• Heavy-duty extension cords: run outdoor-rated 12- or 10-gauge cords from the generator directly to individual appliances. Cheapest, but you cannot power anything hardwired like a furnace or well pump.
• Generator inlet box + manual transfer switch: a licensed electrician installs a transfer switch or a breaker interlock at your panel and an exterior inlet. You run one heavy cord from the generator to the inlet, and selected circuits are powered through your normal outlets and hardwired appliances. This is the correct, code-compliant setup.

Never, ever back-feed power by plugging the generator into a wall outlet or dryer outlet. That energizes your home wiring and the utility lines outside, and it can electrocute a lineman working to restore your power. It is illegal in most areas for exactly that reason. A transfer switch or interlock costs a few hundred dollars installed and is the only safe way to power hardwired loads.

Carbon Monoxide: The Rule That Keeps You Alive

Portable generators are the leading cause of carbon monoxide deaths during power outages, and it happens fast. A running generator produces as much CO as hundreds of idling cars. The gas is odorless and colorless, and by the time you feel dizzy it may be too late to get out.

The rules are simple and absolute:

• Never run a generator indoors, in a garage, carport, basement, shed, or crawlspace, even with the doors and windows open. An open garage door does not clear it.
• Place the generator at least 20 feet from the house, with the exhaust pointing away from all windows, doors, and vents.
• Install battery-backup CO alarms on every level of your home and test them before storm season.
• Buy a unit with a built-in CO shutoff sensor (look for “CO Guard,” “CO Detect,” or PGMA G300-certified). It automatically kills the engine if CO builds up nearby.

Grounding, Fuel Storage, and Safe Operation

Follow the manufacturer’s grounding instructions. Most modern portable generators with a bonded neutral do not require a separate grounding rod when powering equipment directly, but a transfer-switch install may have specific grounding requirements your electrician will handle. When in doubt, ask the licensed pro who wires your inlet.

Store gasoline only in approved containers, outside the living space, away from any ignition source and never near the generator while it runs. Always shut the engine off and let it cool before refueling; gasoline splashed on a hot muffler ignites instantly. Keep the unit dry and out of standing water, and run it under a purpose-built generator tent or canopy if it is raining, never in an enclosed space.

Inverter vs Conventional Generators

You will see two engine types on the market. A conventional generator runs its engine at a fixed 3,600 RPM to produce 60 Hz power, so it is loud and burns fuel at the same rate whether it is powering one lamp or a full load. An inverter generator varies engine speed to match demand, which makes it quieter, more fuel-efficient, and clean enough to safely run sensitive electronics like laptops and modern TVs without a surge protector.

The trade-off is price and size. Inverters cost more per watt and top out lower, though large 7,500-watt inverters now exist. For whole-home backup on a budget, a conventional dual-fuel unit gives you the most watts per dollar. If noise matters, you camp with it, or you run a lot of electronics, the inverter premium is worth it. Many homeowners split the difference with a mid-size inverter for essentials and quiet operation.

Runtime, Maintenance, and Storage

Plan for how long you actually need to run. At half load a 7,500-watt gas unit sips about 0.75 gallons an hour, so keeping it fed through a three-day outage means having 15 to 20 gallons stored safely or a propane supply lined up. Cycling the generator, running it a few hours to cool the fridge and charge devices, then shutting it down, stretches fuel dramatically over running it around the clock.

Maintenance is simple but non-negotiable. Change the oil after the first 20 to 30 hours on a new unit, then every 50 to 100 hours or annually. Keep a spare air filter, spark plug, and oil on hand because auto parts stores sell out during a regional outage. Run the generator for 15 minutes every few months to keep the carburetor clear, or run it dry of gas and store it with the fuel valve off if it sits for the season. A generator that will not start when the lights go out is just an expensive lawn ornament.

Bottom Line

A well-chosen portable generator for home backup is one of the best value upgrades you can make before storm season. Size it to your essentials plus one surge, pick dual fuel for flexibility, and have an electrician install a transfer switch or interlock so you can power your furnace and pumps safely. Then respect the carbon monoxide rules without exception. Get those pieces right and you will ride out the next multi-day outage in comfort while the neighborhood sits dark.