Wifi on and wifi being heavily used are two different states assuming same as Vita.
So I think Mario Kart will have a huge hit to battery life when online.
Also I don't think Zelda is going to be the most battery consuming title. It's a title that also works on wii u for the same gaming experience and that console probably has at least half the cpu performance of Switch. I think Skyrim will be a bigger test as its graphics are more realistic and the engine is more cpu intensive. It's a real test to the performance of a system assuming developed to a high standard and pushing the hardware. Like Zelda though its a single player experience so wifi not required. Playing Skyrim on my windows tablet eats through the battery at a alarming rate and that is with Skyrim set to very low graphic output settings using a custom text file that sets it below normal low quality settings and at a lower resolution than the native resolution of the display just to get it working well on the tablet. The tablet has higher cpu performance than Switch but much lower gpu performance. Something like 50-80 gflops I think.
I couldn't find my tablet shown but this is similar;
https://www.youtube.com/watch?v=zZZexGQB1gA
So you can imagine Skyrim at 720p pushing the limits of both gpu and cpu should really eat battery life. The game is always loading new data and processing a physics engine and other background elements to the game world. Texturing and lighting is realistic with texturing detail even on small graphics. Even looking at a tree stump near the village where you start shows ants crossing over the cut tree trunk.
