Power consumption Duron-Athlon-Core 2

I have been looking at system power usage versus processors. I have a Duron
1.4 GHz tower system that takes a steady 100W (without monitor). If I
replace the Duron with an Athlon XP 3200 the power will increase, but how
much? The CPU will dissipate more but how much more and how much the
faster running MB etc? Everyone says the Core 2 duo is light on energy
consumption but what can I expect the average core 2 duo *system*
consumption to be? When the machine is running 24/7 the total energy
consumption here is significant - with monitor and printer I measured
nearly 30 kW/H in the past 7 days - not very 'green'!
Richard
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