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### Topic: How to calculate AC Watts (Read 844 times)previous topic - next topic

#### Lavan

##### Apr 05, 2013, 09:58 pm
Hi There!

I need to buy an 220V AC to 110V AC converter for my Xbox adapter. Only DC power rating is mentioned on the Adapter as 12 V DC @ 9.6 Amps and 5V DC @ 1Amp.  If I calculate P=VI, total power is coming to 120 Watts at DC.  Will DC wattage is equal to wattage at AC?  What wattage of converter I need to buy to hook up this adapter?

#### Grumpy_Mike

#1
##### Apr 05, 2013, 10:02 pm
Quote
Will DC wattage is equal to wattage at AC?

Only if the adapter is 100% efficient at converting the power. Normally they are between 80 and 95% efficient, so allow a bit of margin.
Don't worry about getting one with too much wattage, make sure the voltage and current output are sufficient.
Don't worry about too much current, the device you attach it to will take what current it needs up to the maximum the adapter will supply.

#### Lavan

#2
##### Apr 05, 2013, 10:14 pm
Thank you very much for your quick reply.  So a 150 Watt 220 V to 110 V converter is best bet?

#### Grumpy_Mike

#3
##### Apr 05, 2013, 10:20 pm

So a 150 Watt 220 V to 110 V converter is best bet?

Yes if it provides the current and voltage you want either a 150W or 200W converter will do the job.

#4
Thank you!

#### retrolefty

#5
##### Apr 05, 2013, 11:50 pm
Quote
I need to buy an 220V AC to 110V AC converter for my Xbox adapter.

In the old days we would have said "I need a step down transformer 220/110 vac."

Lefty

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