How Does Power Consumption Compare Between AC and DC in a Single Device?

In summary: AC and DC power. He is unsure if the voltage supplied by the power source is the same when using DC and AC power. He also wants to know what the max current a device can draw from a 12v battery. When using AC power, a device will draw the same amount of power regardless of the voltage supplied. The voltage supplied to the device is always 120v. When using DC power, the voltage supplied to the device will be the same, but the current drawn will be different. If the device is drawing 500w over a DC power supply, then the current drawn would be 500/0.70=
  • #1
pmpstyles
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Hello, I just came across this site when looking for some info. Not sure if this is a stupid question but I would like to know what the correlation between AC and DC power is when comparing one device. For example if i had a a device connected to 120vac and it drew 500w then the amps would be 4.16. So if i use that same device and connect it to a power inverter on a 12vdc system, it would draw that same power through the inverter, but what would be the draw on the 12vdc side? Is it just simply 500w/12v=41.6amps. I am basically trying to figure how much AC power can be drawn from a 12vdc battery where 50a is the max current the can go through a dc meter. Thank you
 
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  • #2
12 V x 50 A = 600 W. An upper limit (some losses in the DC-AC converter)
But my guess is the battery can't deliver that for very long ...
 
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  • #3
You are quite correct in your calculation of the power needed, but, as BvU indicates, the inverter is not 100% efficient. So you need to divide your calculated result by the efficiency.
So if the inverter were 70% efficient, the current draw would be 41.6 / 0.70 = 59.4 A.
But I don't know what a typical efficiency would be. (I have found a reference that suggests it can be in excess of 90%, which would mean 41.6/0.90=46.2A)

Also, the inverter might not deliver the 120V AC you expect. If it delivers less, then your device might not draw its full 500W, then the 12V current could be less.
 
  • #4
Sorry, I was just going hypothetically. If everything was 100% efficient and a device plugged into a home outlet drew 500w over 120v, then the amps would be 4.16. In theory, if the same device ran 500w over 120v on a 12v battery. What are the numbers for the voltage, amps, and watts coming from the battery and going to the inverter? Is it simply calculating the amps because we know the voltage of the battery (12v), we know that the device used 500w over A/C, then would that give the answer or is it some random number? Hopefully that makes sense.
 
  • #5
pmpstyles said:
Is it simply calculating the amps because we know the voltage of the battery (12v), we know that the device used 500w over A/C, then would that give the answer

yes, as stated in your OP

but remember, as you have been told, it's a long way from the real world, so don't try and use
the figures to produce good infoDave
 

Related to How Does Power Consumption Compare Between AC and DC in a Single Device?

1. What is the difference between AC and DC power consumption?

AC (alternating current) power consumption refers to the flow of electrical energy that constantly changes direction, while DC (direct current) power consumption refers to the flow of electrical energy in one direction.

2. Which type of power consumption is more commonly used in household appliances?

Most household appliances use AC power consumption because it is more efficient for long-distance power transmission and can easily be converted to different voltages.

3. How does AC and DC power consumption affect energy bills?

AC power consumption is typically measured in kilowatt hours (kWh) and is what is recorded on your energy bill. DC power consumption is not usually measured separately, but it can affect the overall efficiency of your household's energy usage.

4. Can AC and DC power consumption coexist in a single system?

Yes, AC and DC power consumption can coexist in a single system through the use of converters and inverters. For example, solar panels produce DC power, but it can be converted to AC power for use in household appliances.

5. Is one type of power consumption safer than the other?

In general, AC power consumption is considered safer because it can be easily transmitted over long distances without significant loss of energy. However, both AC and DC power consumption can be dangerous if not handled properly.

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