How is the cost of a drive calculated?

I saw the answer to another question saying it was just the energy usage from a drive * the cost of home charging per KWh but that doesn't add up for me.

I just went on a drive that was 14.66 KWh and it says the cost was $1.83. That implies $0.148 per KWh but my cost of home charging is $0.28 per KWh so why is teh cost of the drive different from what I expected?