Portable Generators for Home Backup

Who a portable generator suits

A portable makes sense if your outages last hours to a few days, you're home when they happen, and you can live with powering the essentials instead of the whole house. It's the common choice for homes on a well, because a mid-size unit can run the pump, the fridge, some lights and the furnace fan in rotation.

It's the wrong tool if nobody's home to start it, if someone in the house depends on powered medical equipment, or if you want the AC running through a week-long heat wave. That's standby generator territory.

How big a generator you need

Size it by adding the running watts of what you'll run at once, then making sure the generator can also cover the starting surge of the biggest motor. Starting watts are the short spike a motor needs to get going, and running watts are what it draws after that.

Champion's wattage chart gives typical figures:

Use your own nameplates where you can, since the chart is a range. The well pump is the one that catches people out: a 1 HP pump can want up to 4,000 watts just to start. Our generator sizing guide walks through the math.

Conventional vs inverter

This is the main split in portable generators.

For backing up a house on a budget, a conventional open-frame unit sized for your well pump's surge is the workhorse. Inverters cost more per watt, but they're the better pick if you mostly run electronics or care about noise. Champion recommends an inverter for equipment that needs under 3% THD. Big open-frame inverters split the difference, and Champion sells them from 4,250 to 9,000 watts.

Fuel: gasoline, propane or natural gas

Gasoline is the default. Generac calls for unleaded at 87 octane or higher and warns that gas starts to break down in about a month, so add stabilizer from the start. Westinghouse says stabilized fuel can stay in the tank up to six months if you drain the carburetor float bowl.

Propane stores for years without going stale, which is why dual fuel generators are popular for outage backup. You give up some output on propane. Champion's 4000-watt dual fuel inverter drops from 3,300 to 2,970 running watts when you switch fuels. A gasoline-only unit won't run on propane, and Champion says converting one voids the emissions warranty.

Natural gas is the odd one. Standard portables don't run on it, and HomeAdvisor describes natural gas generators as stationary units. Tri-fuel portables do take natural gas, through a connection a qualified pro installs.

Diesel portables exist too, but they're heavy, expensive and mostly a jobsite or farm choice.

Connecting it to the house

You have three ways in, and only two belong on a house panel.

• Extension cords to individual appliances. Fine for a fridge and a lamp. Use outdoor-rated, heavy-duty cords rated above the wattage you'll plug in.
• An interlock kit on your existing panel. It blocks the main and the generator breaker from being on together, and you can power any circuit in the panel.
• A manual transfer switch with circuits chosen ahead of time.

Both panel options need an outdoor inlet box and a cord. Champion says inlet boxes come in 30-amp and 50-amp versions matched to the generator's outlet, typically an L14-30 or 14-50, so check which outlet your generator has before anyone buys parts. Compare the two on our interlock kit vs transfer switch page.

What to skip

• Any unit without CO shutoff. CPSC urges buyers to pick generators that shut off automatically when CO builds up. Champion's version is called CO Shield, and Champion says it's no substitute for an indoor CO alarm.
• "Double male" cords into a dryer or wall outlet. That's backfeeding, and CPSC calls it extremely dangerous.
• Buying the biggest unit you can lift. Fuel burn scales with size. Match it to the loads you'll actually run.
• Mini generators for house backup. A 1,200-watt unit will run lights and phone chargers, not a well pump.

Install and storage notes

Put CO alarms on every level of the house and outside sleeping areas. Keep fuel out of the house, in labeled safety cans. Shut the generator off and let it cool before refueling, because gas spilled on a hot engine can ignite.

Generac says to change the oil after the first 20 to 30 hours and every 100 hours after that. If it'll sit more than 30 days, drain the fuel and run the carburetor dry. Start it once a month under a light load so you find the dead battery or gummed carburetor before the storm does. Keep spare oil and a spark plug on the shelf, because the parts counter will be closed when you need them.