It's definitely possible to use up 100 multi-battles on many days, if perhaps not every single day - depending of course on whether you run campaign or dungeons that take more energy per run. Although it does depend on your level. 

Depending on your level of activity and how it's spread over the day, you could get up to 480 energy from the automatic energy generation (1 energy every 3 minutes, though only when you are below the energy cap).  

Then you can get up to three free energy refills per day (from the login timer, the daily quests and the advanced quests), plus a fifty energy quest among the advanced quests. Once you're at level 60 or above, that's 440 energy. 

That makes 920 energy, in theory, on any single day - without counting the additional energy refills or energy rewards from weekly/monthly quests, login rewards, tournament/event rewards, doom tower, etc. Plus the daily free pack in the store, which often includes a free energy refill as well. And of course you can always buy additional energy refills for 40 gems apiece. 

So yeah, more than enough energy to do 100 campaign multi-battles, or a mix of campaign and dungeons. For lower-level players with a lower energy cap, the numbers will be lower and maybe you can only rarely do the full 100, but you should still be able to do 70-80 or so.