AllenTX

Super solid battery life even with 2+ years of heavy use, no signs of it slowing down. Only thing is it's not very upgrade-able, so make sure you get the amount of RAM you need upfront, and if you are not comfortable with an m.2 swap i suggest the same with the storage space. So it can get a bit pricey. Still worth it over most comparables. 

My recommendation is the XPS13, love mine, newest version are even better. 

Excel is supposed to be really variable power wise there are people who do wildly complicated things with excel that want many threads.  There are also simple applications that really are just a bit of excel.