Reducing power useage to minimum

[peter777]

I have a Dell Latitude D820 with Windows 7 installed. All it is being used for is to listen to the network and display inverter readings. The software is SP-LINK, shown at http://www.selectronic.com.au/sppro/splink.htm

It is not connected to any outside network, only internal. The laptop power usage is still, what I would call, high. It is still using 26W with the screen saver activated. I have taken the battery out as it was old and seems faulty.

How can I reduce the power usage to an absolute minimum ?  The resource monitor shows very little CPU being used, and RAM usage is only 50 % . The HDD is a little bit over half full. There 'seems' to be a fair bit of disk activity. Possibly it is swapping a lot or needs defragmentation ?

Can I remove a lot of programs to reduce the power consumption ? (Google Chrome is installed and I will not need that).

[cdob]

A D820 uses a 945GM chipset.
https://www.dell.com/downloads/global/products/latit/en/spec_latit_d820_en.pdf
26 W is average for this hardware family. Which CPU and graphic card do you use?

RMClock Utility can change CPU VCore.  http://cpu.rightmark.org/download.shtml
However the limitations are hard wired at the CPU. A average mobil CPU runs at a lower voltage too.
https://en.wikipedia.org/wiki/List_of_Intel_Core_2_microprocessors
Undervolt the CPU at low speed http://forum.notebookreview.com/threads/undervolting-core-duo-core-2-duo-by-pin-mod-part-2.365230/

Do you use a NVida GPU?
Undervolt the GPU http://www.guru3d.com/files-details/nvidia-inspector-download.html

Given little CPU being used, no need to remove a lot of programs. The programs seems not to produce CPU load.
Do you use  a virus scanner? Remove this at a internal network machnie.

Given a 945GM hardware area, some power reduction should be possible, but not very much (not half power consumption).
I guess the challenge is with given hardware.
Disable devices at device manager or remove not used hardware, e.g. Bluetooth, WLAN, Modem
http://downloads.dell.com/manuals/all-products/esuprt_laptop/esuprt_latitude_laptop/latitude-d820_service%20manual_en-us.pdf