Idea is to share how much time it takes on your device to reach a full charge with what rom and kernel!
Something doesn't quite add up there, either the asus supply is providing more than 2a (10W) or your battery isn't getting fully charged (calibration is off)
The Z1 has a 3Ah (3.8V) battery, which is at least 11.4Wh.
With 100% efficiency (no heat generated during charging and device off) you would only be able to charge the battery 87.77% in 1 hour.
It is possible at the kernal level to specify max charging current so a custom kernal may have a lower charging rate to preserve the battery, if the rom uses a stock kernal then something might be draining the battery whilst on charge (google / data sync etc)