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Does my garden 250 watt AC/DC transformer consume 250 watts when I only have 50 watts of DC LED lighting? Answered

So the question is:  Does an AC/DC transformer consume its max wattage even when it's not maxed out on the DC side?  I have a 250 watt transformer that steps down to 12V for low voltage garden lighting.  Is it always drawing 250 watts?  Added up, I have about 50 watts of LED low voltage fixtures.

Back in my military days, when we were in Europe, we had these 300, 500, and 1000 watt transformers to step Europe 240V down to US 120V, and we were always told those transformers drew their max capacity even if a small radio was plugged into it. I argued it prolly didn't because of the conservation of energy thing.

I can always put a kill-a-watt meter on it too I guess.

Thanks in advance!



3 years ago

No, it will take what it needs for the LED's and an extra bit for the transformer losses, maybe about 60watt total.

Jack A Lopez

3 years ago

I can always put a kill-a-watt meter on it too I guess.

Well why don't you do that?

Maybe you want to know what the answer is supposed to be first?

It's like the other answerers have told you. A well designed transformer dissipates much less power than the load it is designed to supply.

But don't take my word for it, or anyone else's. What you really should do is test your transformer with your Kill-a-watt (r) meter. Measure how much power it takes to supply transformer with 12-volt lights on. Measure how much power it takes to supply just the transformer with the 12-volt lights disconnected. Then see if those are different numbers.