So recently, during Irene, I learned that my car's lighter outlet was insufficient to power a sump-pump (hello, two inches of water in the master bedroom) Thankfully, the car's circuitry was fine but I don't think the adapter works anymore c'est la vie. Even more thankfully, this is the second time my house has flooded, so we knew how to protect everything above the sub-floor save the carpet (huzzah?).

Anyway, my wife and I have come to the conclusion that maybe it would be a good idea to get a generator to power the sump-pump next time. The problem is that I know almost nothing about what I would need.

My only major requirement is that it is able to run a sump-pump (batteries are not sufficient -- power can go for hours during a storm). It would be nice (since I need to get one anyway) if it could run my well pump and my refrigerator too (because keeping the food good and the water running is something I consider worthwhile).

Ideal world -- I would like something which an idiot can run and something I won't need to worry about too much between uses (I'm a developer, I can take a computer apart and put it back together blindfolded, but when it comes to maintaining equipment, I'm basically lost), and something which is inexpensive would be nice too.


You should hire an electrician to help you with this, since you don't sound qualified to wire up a generator properly. She can help you figure out the right way to do this. However, it's good for you to be well-informed going in to this. So:

Generators are rated in several ways:

  • Peak load. Starting a motor (like a pump or fridge compressor) draws a lot of current (amps) for just a moment. You want to make sure your generator can handle that.

  • Nominal load. If your fridge and sump pump and well pump are all running at the same time, can the generator handle the load? Add up all the loads of what you plan to run. I've ready that it's good to keep a generator running at 50% - 75% capacity most of the time, but that was in an off-grid RV context; it may or may not apply to you.

  • 240V vs. 120V. Smaller generators usually only put out 120V. If your sump pump or well pump requires 240V, you'll need one that can do that.

  • Fuel type. If you already use propane or natural gas for heat, it can be convenient to use that fuel for your generator. Otherwise you'll need to keep gas or diesel on hand. Diesel is less explosive. Gas engines are easier to work on. Use a fuel preservative like Sta-Bil to keep the gas fresh.

Be sure to exercise your generator regularly, per the manufacturer's instructions. (My RV generator wants to run for 30 minutes at 50% load every month.)

A permanently-installed generator must be on a transfer switch. This will disable the connection to the power grid when the generator is providing power. This is critical to protect line workers doing repairs on the grid after a storm. You can even have the whole system be automatic, so if you are evacuated or on vacation the generator can kick in and save your stuff.

Think about where you want the generator. Close to the transfer switch & main breaker panel will reduce cost of wiring.

The smaller your generator is, the cheaper it will be to buy, install, maintain, and run. A simple way to approach this problem is to buy a portable generator that will run one of those 3 loads at a time (sump pump, well pump, fridge). Plug each appliance in to the generator one at a time, as needed. Pump out the basement, then fill the well reservoir, then draw down the fridge. (Filling your fridge with bottles of water will add thermal mass.) Remember that the generator must remain outdoors, to avoid carbon monoxide poisoning. This only works if your pumps are plug-in, not hard wired, and if they're close enough to run a reasonable extension cord to them from the generator.

  • 1
    Great advise Jay. +++ Excellent description of what is needed for a permanent install. Propane or natural gas is the way to go if he can afford it, less maintenance and trouble free. My portable 5000 watt gasoline gen finally bit the dust during Irene, but then it has logged thousands of hours, several ice storms, hurricanes and powerless job sites. Looking at a Generac natural gas unit with auto transfer now. Sep 6 '11 at 9:45
  • 1
    For your sump pump and refrigerator, you can do with a fairly small unit (size it as Jay suggests) and use extension cords. You cross a line when you add the well, however, as it is hardwired (and most likely 240 volt), requiring a proper transfer panel. You can get a portable generator with the required 4-wire 240/120V cable to connect to a transfer panel; if you go that route, consider adding your furnace to the transfer panel as well so that you can keep your pipes from freezing during an extended cold-weather outage.
    – TomG
    Sep 7 '11 at 1:01
  • I use a small (500 watt?) gasoline generator with extension cords to the sump pump and fridge and freezer. I ALSO have a battery backup secondary sump pump (actual second pump in the sump, with battery on it). This means that no matter what happens, I have several hours to get the generator up and running before I have a water problem. Feb 1 '12 at 12:19

I know this is an old question, but I wanted to mention another option if your main concern is the sump: a Sump Bump Battery Backup System. This is a system with a battery (about the size of a car battery) that charges off your AC power, and when main power goes off, the sump pump can run off of the battery.

The model I have says that it can power a sump pump for a week of "normal usage" (whatever that is). It also has alarms to let me know when AC power dies (in case a breaker blows), when the battery is low, when the pump has a problem, etc. I believe you can buy these as combined packages with sump pumps, or as separate systems that sit between your existing pump and AC power.

I did not install the one we have now, but based on the instructions, I think a reasonable diy-er could handle it, and certainly a plumber or contractor could.

I would recommend that anyone with a basement with any risk of flooding look at one of these systems, or at least at a water level alarm. I too have suffered through basement floods, and they are extremely damaging and utterly demoralizing.


In addition to battery-powered backup sump pumps, a somewhat simpler backup solution (provided you have city water, which unfortunately the OP does not) is a water-powered backup sump pump. Unlike a battery-operated system, this can theoretically run forever.

Some info from a manufacturer of a water-operated system

A 'This Old House' segment on installation of a water-operated system

  • I've been in power outages that took out municipal water, too.
    – Jay Bazuzi
    Jul 11 '12 at 1:39

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