Did you know, how much power need desktop computer when it is idle? Whole 4.7W when it's off (motherboard is still powered, Wake On LAN may be active etc. Pretty much. huh? This is old Sempron 2300+ with ATX power supply.
When it's powered on, it uses about 80W (idle). Box alone (CPU, motherboard, HDD), without monitor. Running burnk7 increases power draw to 106W.
If you have such an ancient hardware and use it often - consider buying new laptop. It will be probably a lot faster and may return on energy bills quickly.