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DAS26miles's avatar
DAS26miles
Explorer II
Apr 28, 2020

Modified Sine wave inverter for seldom used microwave

I know everyone is going to say to get a Pure sine wave inverter, but I can't justify the investment just to power the microwave for a few minutes a day while camping. We won't be using it much, just at campgrounds that have limiting generator hours. We have other options instead of the microwave so it's hard enough spending $140 let alone over $300 for such an occasional use.
  • I tried a MSW inverter with my microwave and wasn't impressed. A cup of water took 2 mins 30 seconds to boil compared to 1 min 10 seconds with a PSW inverter.
  • Lots of coach builders are still using MSW. Ours came with one, and the micro worked ok, but it did heat slower and made a buzzing sound not heard on pure sine.

    I have since replaced it with a PSW but not because of the micro.

    Be sure your batteries are up to it. Takes about 140 amps current to run our kitchen appliances.
  • Do it right with a PSW inverter...save a microwave’s life and other sensitive electronic devices. But since you know what everyone will say...
  • time2roll wrote:
    Just skip the inverter.


    OP wants 120v outside gen hours. Like making toast with a real toaster early AM, then recharge the batts later in the day during gen hours.
  • Other things don't like msw either. Everything runs with psw.
  • We always used a MSW inverter for MW with no troubles. Check the back of the MW for its real 120v input watts requirement and then get the inverter that will do that.

    Eg, a "700w" Danby wants 1050w input. A "1000w" might want 1500w input. AND the inverter has a continuous rating that is less than its "name" so eg, a "400w" will run 320W and a big "2000w" will run something less. So check both actual spec figures for matching them.

    It is true the MSW will take longer to heat something up than a PSW, but it is hard to notice in real life. EG your spud is done when you can stick a knife in it, but when is that exactly?

    You need enough battery to run the MW from the big inverter even with MSW. Follow the installation instructions for the inverter wiring gauge and fuse once you choose the inverter.
  • Many still use a modified sine wave inverter, no problem there. Just know the microwave will be producing less heat.