- - posted in Ancient Archives

The lights at home did some disturbing flickering last week, so I’ve started thinking about replacing my dead UPS.

A basic UPS can handle about 400w. My PC’s power supply can provide up to 450w, but how much does it actually use?

I’ve now got a gadget that connects between a plug and mains socket and gives a live reading of the watts being consumed. Power usage on the PC ranges from 90w to 120w. It was fascinating to see power consumption rise while email was being downloaded. We tend to think of the virtual activity within computer networks being completely distinct from the real world, but in reality even an email attachment has a carbon footprint.

There was one disturbing discovery. The PSU is a recently bought Antec HE, an ATX2.2 ‘high efficiency’ power supply. It gives off less heat, and has an 85% efficiency. This is all very good, and might well account for the lower than expected power usage. Unfortunately the power meter showed that when the PC was turned off using the soft-power button, and should have been almost completely off, it was still consuming 20w! Twenty watts is quite a lot of power for what I assumed was a small circuit to detect a powerup request. To put it in context, a Nintendo Wii games console uses less than 20w when being used to play a game. The PC was doing nothing.

I normally avoid ‘standby’ modes and had no idea I was wasting so much power. I’ve now set the PC to boot when ‘power is restored’ and then switch it off at the ‘hard’ switch too.