Electricity costs much for me so I prefer the lowest possible consumption.

I can get to the numbers (performance wise) that you posted but not with 145-150w. How did you measure that?

I use the following method for measuring gpu power draw:

• Remove all gpus and risers from the rig. I mean unplug them completely
• Measure idle consumption of the rig.
• Reconnect all gpus and risers
• Measure mining consumption of the rig.
• Perform a  mining - idle consumption and divide by the number of the gpus

Keep in mind that if you have your GPUs or risers plugged in (even without having them mining) they do consume power.
Also, I only measure power consumption using a wall meter.

Did you use that methodology for your measurements @greatauror28 ? What brand of RX 580 do you have?