I have same problem too. I am using early 2015 13" Retina MBP. Just installed Mojave yesterday, but I found that battery drained 10% in 30mins under new OS. That never happened the day before when I was still using Sierra (When I was using Sierra, a fully charged battery can be ran a whole day over 10hrs, but now I believe 6hrs will be the max for my MBP). Checked from system information, battery is healthy in normal condition, Cycle Count only 490.