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Old 30-01-2013, 17:39   #1
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1000 Watts at 240 Volts AC is How Many Watts at 12 Volts DC

Hi There,

I have scrounged the net and found other amps to watts and voltage calculations, but either haven't found or don't know how to find the answer to this question.

Does anyone know how to work it out as im trying to figure out the consumption or a device that i want to run off my inverter.

Thanks in advance

Matthew
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Old 30-01-2013, 17:46   #2
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Re: 1000 Watts at 240 Volts AC is How Many Watts at 12 Volts DC

VIR
1000w divided by 240v=4.2 amps
240v divided by 12v= 20
20 x 4.2=84 amps@12v
12x 84=1008 watts

rounded off the initial ampage but a 1000watts is a thousand watts!
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Old 30-01-2013, 17:48   #3
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Re: 1000 Watts at 240 Volts AC is How Many Watts at 12 Volts DC

Matthew--

Watts is watts = Amps mutiplied by Volts. 1000 Watts at 240 volts indicates an energy burn of 4.17 amps. 1000 watts at 12 volts indicates an energy burn of 83 amps. It's the amps that matter.

FWIW...
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Old 30-01-2013, 17:58   #4
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Re: 1000 Watts at 240 Volts AC is How Many Watts at 12 Volts DC

Power (Watt) = I (Amp) x V (Volt); one of Ohm's laws. The wattage resulting from either an AC or a DC circuit is the "same quantity". It gets a little complicated when an inverter is involved. Reputable manufacturers of inverters publish charts depicting the actual loss of power from the conversion. Use a ball park figure of 45% loss, to get a rough estimate. (Make sure your circuit is "fused" correctly to avoid a fire.) Mauritz
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Old 30-01-2013, 18:13   #5
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Re: 1000 Watts at 240 Volts AC is How Many Watts at 12 Volts DC

The Ampere calcs above are for simple resistive loads. If there is a large motor or big switching power supply being driven the calculation must consider the power factor and start-up current.
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Old 30-01-2013, 18:27   #6
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Re: 1000 Watts at 240 Volts AC is How Many Watts at 12 Volts DC

What make and model of inverter? Look up manufacturer's specs for estimated loss.
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Old 30-01-2013, 19:47   #7
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Re: 1000 Watts at 240 Volts AC is How Many Watts at 12 Volts DC

A BIG THANK YOU EVERYONE

i dont know why that was so hard for me to figure out, but you guys all nailed it right on the head, cheers.

Matthew
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Old 30-01-2013, 20:14   #8
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Re: 1000 Watts at 240 Volts AC is How Many Watts at 12 Volts DC

Wait, are we talking RMS or peak to peak?
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Old 30-01-2013, 22:14   #9
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Re: 1000 Watts at 240 Volts AC is How Many Watts at 12 Volts DC

Quote:
Originally Posted by resilientg View Post
Hi There,

I have scrounged the net and found other amps to watts and voltage calculations, but either haven't found or don't know how to find the answer to this question.

Does anyone know how to work it out as im trying to figure out the consumption or a device that i want to run off my inverter.

Thanks in advance

Matthew
1000w @ 240v-ac is equal to 1000w @ 12v-dc plus or minus conversion inefficiencies that will depend on what method of conversion you use and which side has the 1000w vs which side needs the 1000w.

If you need 1000w on the ac side, then you will need more than 1000w on the dc side, I'd guess 100amps to be safe.
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