I have in my possession both the SP4 M3 and the SP4 i5 (4GB/128BG) for the next week. So I decided to run my own battery life comparison. I consider the following results just a dry run. I plan to run these 2 PCs until they shut down sometime this weekend. I went to endlessvideo.com and picked the same video to run on both PCs. When I came home from work today, I turned off the sound (to keep my sanity) and just let them run from a fully charged state. 1 hr 3 min -- i5 87% remaining -- M3 89% remaining 2 hr 5 min -- i5 73% remaining -- M3 76% remaining 3 hr 0 min -- i5 60% remaining -- M3 65% remaining I think I may have handicapped the i5 a bit because I had 4 other Edge tabs open at the start. I closed those 4 extra tabs about 5 minutes after the start. I'm no tech expert, so if anyone has any suggestions about how to make the comparison more fair, please let me know so I can do the best possible test this weekend.