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Power Supply Efficiency

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June 16, 2010 5:08:22 PM

I have a 1000 Watt Power Supply right now. If I had a power supply with a wattage rating of less, would my computer use less power?
A Laptop uses: 80 Watts
My PC Idle uses: 250 Watts
My PC In A Game uses: 450 Watts
An Energy Efficient Lamp uses: 25 Watts

My Question is if I had a power supply with a wattage rating of less 1000, would I see lower numbers when playing a game or when my computer is just on and not in use? Or does the power supply wattage rating not effect the overall power consumption of your computer? Does having a power efficient power supply effect the overall power consumption of your computer?
a c 272 ) Power supply
June 16, 2010 5:19:30 PM

Its entirely dependent on the efficiency of the unit, if your PSU is 85% efficient at that load level, and you replace it with a smaller unit that is still 85% efficient at the same load, your power draw will remain the same. Most PSUs are most efficient at about 50% load which is why a 1kW unit might make you draw more power but it really depends on its efficiency. If your 1kW unit isnt 80+ certified and you replace it with an 80+ bronze unit you would drop your power draw by a bit.

If your system needs 400W DC, and your PSU is 80% efficient at that load level you will draw 500W from the wall, if your PSU was 90% efficient you would only draw 444W from the wall.
June 16, 2010 8:12:42 PM

hunter315 covered most of the points pretty well. Assuming that the efficiency of your current supply is the same as it's smaller replacement, then there would be no real change in power draw. It's not always drawing 1000W, it's just drawing whatever your system demands.
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a c 144 ) Power supply
June 17, 2010 5:39:58 PM

Pyroflea said:
hunter315 covered most of the points pretty well. Assuming that the efficiency of your current supply is the same as it's smaller replacement, then there would be no real change in power draw. It's not always drawing 1000W, it's just drawing whatever your system demands.

Up to the 1000 watts in this case.
a b ) Power supply
June 18, 2010 4:43:35 AM

A 1000w PSU can deliver up 1000w of power.

However, actual power consumption is higher and it depends on the efficiency of the PSU. A PSU that is certified 80PLUS is basically guaranteed to have a minimum 80% efficiency across all loads. PSUs without this rating can have an efficiency as low as 65%.

1000w PSU @ 65% Efficiency = 1000w/.65 = 1538.5w maximum drawn from the A/C outlet

1000w PSU @ 80% Efficiency = 1000w/.80 = 1250.0w maximum drawn from the A/C outlet

The extra watts are wasted as heat.
a b ) Power supply
June 19, 2010 2:24:17 PM

what are your specs and what psu?
the other pretty much covered it. however, most people dont need a 1000w unit, but end up going for high wattage and low quality, and end up wasting more power (due to low efficiency), than if they just bought a high quality 750w unit.
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