I run a weather station that uploads to Weather Underground, and I run a small weathercam server app on a Dell D610 laptop that was given to me.
I also run AHP on the same machine.
It has 1G ram and a 250 M harddrive.
The weather station app writes to the harddrive every 10 seconds so it never spins down.
I used to use a cheap, stripped down desktop for everything before the laptop was given to me.
I do have a kill-a-watt meter and did some power testing and the laptop won out.
The desktop draws 102 VA and 65 watts (no monitor)
The laptop draws 70 VA and 28 watts (no monitor)
The advantage of using a laptop is that you have built in battery backup, and don't need a UPS.
The weather station (Davis Vantage Pro2) has battery backup also.
The only thing that does NOT is the network switch, but uploads to Weather Underground resume when power is restored anyway.
The Kill-A-Watt is is great tool to see just how much power is consumed by all your appliances! I have the EZ model (a little more expensive), but it calculates what the cost to operate the device is by hour/day/month/year, so you have a good idea! I found it at HomeD for the cheapest, but there may be cheaper yet.
The only thing I wonder about is the reliablity of using a laptop 24/7. The fan and heatsink needs to be cleaned regularly as they do get clogged by dust very easily.
They are designed to run warmer than a desktop, but the issue I have is the 24/7/365.
I would think a notebook or a newer laptop would draw even less, but I still wonder about leaving it on all the time.
I will just have to see how long it lasts. Any input on longevity of a laptop or notebook???