No generator...use car?

My husband and I have been debating the need for a gas powered generator to power our basement sump pump in case of a power outage. My husband feels that we could plug our sump pump into the adapter and run it from our runnuing car. I’m concerned that this would drain the car battery…then we’d be without sump pump and car!! Can anyone help?

Do you have the input wattage (or amps of current draw) for your basement sump pump?

Typically the smaller lower wattage automotive DC->AC adapters can run for a long time without affecting the vehicle’s alternator or battery. However, the larger ones will get whatever current they can from the alternator and the rest from the battery - resulting eventually in a dead battery.

That idea will most likely work selecting the proper size inverter for the motor. But it sure isn’t very efficient running a engine with say around 180 horsepower to do a job that a 5 horse engine could do. Instead of spending the money for an inverter I suggest you get a generator or a UPS system.

If you live in an area where needing the sump without power is a recurring possibility you really must set up your emergency supplies properly. This includes actually buying a generator and remember to add Stabil to the fuel supply so it will always be at the ready.

Some other options you might want to consider are either an AC/DC sump pump, a 12VDC back-up sump pump, or a water powered sump pump. These will work if the main sump pump fails or loses power. However, if your house is supplied with well water, the water powered sump pump won’t work because if the power goes out your well pump motor won’t work. I have a 12VDC back-up sump pump and saved my basement from being flooded a couple of times.


How long is your typical power outage? You could just buy yourself a car battery and keep it hooked up to a trickle charger and at the ready. It should be able to run the pump for a few hours at least and if it’s out longer you can start the car and use it to recharge the battery.

The emergency power supply idea would be a good idea, but would also have the drawback of not lasting as long, so if you’re in one of those places where the power goes out for hours and hours or even days you might still need to fire up the car or break down and buy a generator.

Note that you’d also have to get the right kind of inverter. A modified sine-wave inverter, or a square wave inverter, won’t drive some a/c motors. You need a true sine wave inverter capable of driving enough wattage to drive the motor.

A UPS designed for a computer usually falls in the square wave as well- I couldn’t use one to drive my garage openers, I found out, even through it drove the lighting just fine.

The motors on sump pumps are AC powered. A 12 VDC car battery won’t run an AC motor.


A 12 VDC car battery will indeed run an AC powered sump pump using an inverter.

However, it won’t run the sump for very long. Take an average sized 1/2 horsepower sump. It draws 7.6 amps at 115volts. That’s about 800 watts. Using a 12v->120v inverter, means it would draw about 66 amps from the battery at peak load and probably slightly less at normal runtime. A 12v battery won’t remain charged very long with that kind of current draw.

Look at his reply. Is the word inverter even mentioned?


12VDC sump pumps (with 12V motors) do exist.