what size inverter to buy?

Leehamrick
Leehamrick Registered Users Posts: 17 ✭
in Solar Beginners Corner #1
I have been looking at inverters and I'm not sure what watt to buy. I'm not going to run much stuff
T.V., Computer, Radio and maybe some other small stuff like a cell phone charger.
How many watts will I need?
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #2
    Re: what size inverter to buy?

    How many Watts in total will you use at any given time?

    Any one of the items listed is bound to be <200 Watts, but put them all on at once and you could have >400 Watts. That's the trick.
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  • Leehamrick
    Leehamrick Registered Users Posts: 17 ✭
    #3
    Re: what size inverter to buy?
    Cariboocoot wrote: »
    How many Watts in total will you use at any given time?

    Any one of the items listed is bound to be <200 Watts, but put them all on at once and you could have >400 Watts. That's the trick.
    Ok I see,, So if that's all I'm going to run a 1000 watt converter should be more than enough?

    And a quick question,, If a product has the amount eletric it uses listed in amps how do I convert that to watts?
    Like how many watts is 7 amps?
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  • unyalli
    unyalli Solar Expert Posts: 121 ✭✭
    #4
    Re: what size inverter to buy?

    This the very first thing you buy.

    Kill-a-watt

    Then measure actual usage.

    - Jeff
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #5
    Re: what size inverter to buy?

    What Jeff said, for accurate answers.

    The reason being that the numbers listed on things are not necessarily what they actually use. This seems contrary and even illegal, but it is often the case. Maximum Amps will be listed as Amps, average Amps may be listed too. So something that says it is "3 Amps" and "120 Volts" should be 360 Watts, but in actual use it may draw a fraction of that amount. What's worse is that some motors may draw more than the listed rating because their actual current demand will depend on how much mechanical effort they have to make.

    A Kill-A-Watt is the best $30 you'll ever spend. :D
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  • waynefromnscanada
    waynefromnscanada Solar Expert Posts: 3,009 ✭✭✭✭
    #6
    Re: what size inverter to buy?
    Leehamrick wrote: »
    Ok I see,, So if that's all I'm going to run a 1000 watt converter should be more than enough?

    And a quick question,, If a product has the amount eletric it uses listed in amps how do I convert that to watts?
    Like how many watts is 7 amps?

    Two things:
    1) If you can keep your consumption to 50 or 200 watts at any one time, it would be a total waste on two points to purchase a 1000 watt inverter.
    A) It would be a waste of money to buy a more powerful inverter than needed.
    B) The larger the inverter, the greater the drain on the battery just to keep the inverter running.
    2) It's not simple to come up with watts consumed by AC loads as many such loads have poor Power Factor. That's where the Kill-A-Watt meter comes in. Also both the wattage and amperage listed on items are often way off base, and are thus for these purposes, quite unreliable. Thus again, the Kill-A-Watt meter.
    OH! And 3) Seriously consider a Pure Sinewave inverter, as some electronic items such as cell phone chargers, cordless drill chargers etc won't work properly on MSW, and may even emit smoke as they "give up the ghost".
    From what you've told us so far, I would suggest you have a serious look at this inverter: http://www.morningstarcorp.com/en/sure-sine
    I actually power much of my house on this inverter, far, far bigger loads than you have listed, and it's been doing it 24/7 for almost 6 years now. What is it running?
    6 outside lights, all my inside lights, Sat TV receiver, TV, computer, several chargers, stereo etc, and yes, it will and does run all these at once.
    And it also runs my slow cooker!
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