Buying a Used Generator? Check These 7 Things First

A used generator is worth buying only if you will run it the way the health agencies say to: outdoors, more than 20 feet from windows, doors and vents. The price of the machine matters less than where you put it. Carbon monoxide, the gas a generator's engine gives off, has no colour and no smell, and the CDC says it kills more than 400 Americans a year in cases not linked to fires.

A generator is a safe deal outdoors and a deadly one indoors, and no price makes up for that.

Winter storms and summer thunderstorms can both knock out power in the DC area, and a secondhand generator looks like an easy fix. Here is how to buy one without bringing home a problem.

1. Where it will run decides whether you should buy it

Before you look at a single listing, find the spot. The CDC says to run a portable generator outdoors, more than 20 feet from windows, doors and vents, and never inside a home or garage, even with doors and windows open. Ready.gov gives the same distance and adds attached garages to the list of places to keep clear.

If your home has no safe outdoor place with that clearance, a generator is the wrong tool for you this winter, however cheap it is. Treat 20 feet as the number to follow.

2. Size it for the start-up surge, not just the running load

A motor needs a burst of power when it starts. We Energies, a utility, explains that you should size a generator for starting wattage, which is higher than running wattage. For most motorized items it says to multiply the running wattage by 2.5, and by 7 for well pumps, air compressors and air conditioners.

The same page lists these running figures:

Seattle City Light shows the simple method: add up what you want to run. Its example is two 60-watt lights and a 750-watt refrigerator, which points to a 1,000-watt generator. Write your own list, then check the label on the used unit. Do not trust a seller's "it runs everything" claim.

3. Look for the signs of a generator that was stored badly

You cannot test every part of a used engine in a driveway, but you can look. Check these:

1. The nameplate. Is the model and wattage rating legible and does it match the listing?
2. The cord outlets. Look for cracks, burn marks or loose sockets.
3. The frame and fuel tank. Rust, dents or a gas smell are reasons to walk away.
4. The pull cord or start button. It should start without a long fight.
5. The paperwork. A manual, or at least a model number you can look up, lets you read the maker's own warnings.

Ask the seller to run it for you, outdoors, while you watch and listen. A unit that stalls, surges or smokes will not get better at your house.

4. Check the model against recalls before you hand over cash

Safety recalls are one of the few things a seller may not know about. Our earlier guide, a 5-minute recall test before buying secondhand, walks through how to search by brand and model on the government's recall site. Do it with the model number in hand, on your phone, before you pay.

5. Buy a CO alarm in the same trip

The CDC advises battery-operated or battery back-up carbon monoxide detectors near every sleeping area, with the batteries checked when you change the clocks each spring and fall. Ready.gov says to put working detectors on every level of your home, in central locations, with battery backup.

The CDC also says to replace detectors per the maker's instructions or every 5 years. If you are not sure how old yours is, our guide to smoke and CO alarm replacement dates shows how to read the date on the back.

6. Plan how the power gets from the generator to your things

There are only two safe ways to connect a portable generator:

• Straight to the appliance. Seattle City Light calls connecting directly to the load the safest method, using an extension cord from the generator to the appliance. We Energies says to use only UL-listed, three-prong cords, and Ready.gov asks for heavy-duty cords.
• Through a transfer switch. A transfer switch installed by a licensed electrician isolates your household circuits from the grid.

The one way that is not safe is plugging the generator into a wall outlet or house wiring. Both utilities say never to connect a generator to household wiring without a transfer switch. The reason is backfeed, which can send power out onto the lines and endanger utility crews and children. We Energies adds that it can damage the generator and connected equipment. Seattle City Light also says that opening the main breaker to isolate wiring is illegal and unsafe.

Budget for the cords and, if you want the whole-house route, the electrician. A cheap generator that needs expensive cords and a switch is not so cheap.

7. Fuel and fire habits

Ready.gov says to keep the generator dry and protected from rain or flooding, and to let it cool before refueling. It also says to keep generators and fuel outdoors, at least 20 feet from windows, doors and attached garages. Follow the manufacturer's instructions carefully.

If you cannot answer "where do I store fuel and how will I keep the unit dry?" you are not ready to buy one.

Know the warning signs

The CDC lists the common symptoms of carbon monoxide poisoning as headache, dizziness, weakness, upset stomach, vomiting, chest pain and confusion, often described as flu-like. It warns that people who are sleeping, intoxicated or drugged can die before they notice any symptoms. That is why alarms matter more than your nose. If an alarm sounds or you feel these symptoms while a generator is running, get outside into fresh air and get medical help.

The bottom line

Buy a used generator when you have a safe outdoor spot, a sized-up wattage list, a model number you have checked, working CO alarms and the right cords. Skip it when any of those is missing. For stock that is checked, priced and ready to collect, browse what is on the shop, or keep a close eye on the auctions, where our guide to winning without overpaying helps you set a number first. For how DealsDMV works, see our help page.

If this saved you a mistake, send it to a neighbour who is planning for storm season.