Hi Guys,

I want to find out if I could run a fridge and a well pump from a modified sine wave inverter?

Thank you much,



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My vote is no on the fridge, from bad experiences I just don't even try doing the fridges. But, there are certain mini fridges etc. that you see in old trailers etc. that you can run no problem on modified sine wave inverters. You can even run any voltage [well, 120 and lower] and it won't hurt them.

Give us a more info so the "real scientist" here can give you a better answer. Make and models etc.

      I won't say it can't be done, however! You will be beyond the design of the motors and starts will be hard and there effiency will be low. It will make for short motor life.

Thank you very much!

I thought so, but wanted to hear it from people with direct experience.  So, now I have to find out which is the cheapest pure sine wave inverter that would do 1000W peak (or better yet, 1,500).  My well pump consumes 7.8A at 240V.  The fridge is much better - 170W.  The above do not include the peak/start draw.

Thanks again,


I know your pocket book doesn't want to hear it but my best advice is to figure out what those peak watage demands are that you need......and double it. That's the number you are looking for in an inverter.

     Bill from the woods again!

    If, stress the if,  You want one that will handle near anything you want to do, including some expansion! Try the sunforce 2500 watt. It will cost $500 to $600 but is a nice unit and you get the remote on / off control. I got mine at walmart. I have seen them a bit cheaper sense, and for sure higher! Sunforce also builds a 1000 watt that I'd expect to be a nice unit as well, haven't had one in hand however.

    Mine was turned on and has stayed that way, 24/7! Never missed a beat. By going bigger capacity it will allow far better starting response on the heavy loads. It also will run cooler. I also own a smaller wagan, also a nice unit. I have two systems one big one and a little one that powers just my table lite, computer and a small TV. It has the wagan hooked to it. Both units have given realible service and I'm pleased with both.    

    I just noticed that the well is 220 volt. I don't no of any cheaper price 220 volt inverters. You could change out the pump motor to 110 volt . The 220 volt rating you gave will double running 120 volts, regardless by your specs that pumps working real hard on 1800 watts! Volt's times the Amp's is wattage.

Thanks, Ray; Thank you, W.R.

I actually like the $500 price.  Ray scared me to thinking $2000 up.  Would using two of the Sunforce 2500 watt provide the two phase for a 220?  With two battery banks (read - 2x two12V batteries) I could get two separate lines to make 220?  That's what I was thinking.

I appreciate the help I am getting.


I wouldn't try that Luby, some of the guys on the forum have explained why it doesn't work. Sounds good in theory though, but it doesn't work. Get yourself over to Hillbilly Genes page and search and scan of of his responses and post. He has some great stuff on this.


     Mr. Ray is correct and Mr. Gene is no dummie either!

   First, you can change the pump motor out to a 110 volt fairly cheap, mine is a 110 volt deep pump. 

   On tieing inverters together, the problem is they won't be exactly in phase leaving a strange wave form on the output. In the old days ( 70's ) we had some inverters that could be keyed together and would return a great sine wave output, they however were very expensive. Something no one seems to have used is a transformer or auto transformer, 110 to 220. The cost shouldn't be terribly high and the output would be great!  

     Dinner time in the midwest!


I have been running my Frigidaire, 26 cubic foot refrigerator on a Power Brite 1100 watt inverter (mod syn wave) for, well, just over a year now with no signs of any problems...I did add 2 more 125 Ah batteries to the battery bank yesterday, making it a 6 battery bank, and this was done because the 1500 watt surge of the frig compressor will knock a weak charged bank down to a close to dangerous level of charge, this will happen early in the morning, when the sun/panels can't quite compensate for the surge/draw....once the sun comes to the south, I am fine.

I'm not saying you should try this, I am saying that it works fine for me, with this frig and this inverter....the well pump? IMHO, buy a generator with a 220 vac plug and wire up a transfer switch to switch to the generator during a power outage....you will be hard pressed to figure a way to use solar/batteries to run on 220 to drive the well pump...ask me how I know...

Thank you for writing, Bill.  Yes, I am asking how you know - you obviously tried it.

It would be very hard to change the pump with a 110V one.  I already have a gen. with 220AC and a transfer switch.  I live in a rural area, away from a small town, which delays the grid repairs and if I run out of gas, the one that comes out of my behind will not help me much ;-)

I thought to ask you, and the other guys here, about the following.  If I "team up" an inverter, providing a single phase 220, feed this into a transformer which converts it to 3 phase 220 could I use two of these phases to run the pump?

Thank you, to all of you guys, who shared your experience to help me.



   Bill here. Got ta give ya credit for trying!

   First, I say this morning that another Bill, Bill K is running his fridge on modifided wave. I didn't say one couldn't do it, I did say it's not a real good answer. These motors are designed to run on a nice power company, or generator provided sinewave. For good starting curves and effiency they need that.

    For 3 phase, I would take the single phase power sourse and run a 3 phase motor on the single phase, the other windings will now generate the other phases, it's called a rotoary phaser and give a nice clean 3 phase output. It can be build from basic scrap parts and they work very well if kept within spec. I no of no 3 phase inverter, may be some I just havent ran accross one.

    That said, 3 phase is a rare thing on a homestead. It's used more, far more! in heavy industry for larger horse power motors. IThree phasewould have some of what your looking for but also would provide things I don't think you want or need, it's used in industry almost exclusively.

    I also live out between towns! Our power however has for over 10 years been far more dependable then when we lived in the cities!

    As to how I no what I no?? I at one point owned a motor generator repair shop, worked on many diesel stand by plants. Prior to that I was a factory rep on industrial abrassive equipment specializing in the solid state controlls, traveled the entire U.S. and a few foreign countries. I then after a divorce went to work on heating and cooling equipment, what I had a true deploma in, till I retired. I attended lots of schools over the years and tought a few on this journey.

   A thought, someone must build a 220 single phase, with 110 center tap inverter. We can't be the only folks looking at this. If I get time later I will do some homework on this, and I'll post ya if I find one.

    Time for lunch here!




As an option, not real cheap either, but you could look into an edgestar 12v/120v unit.


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