It depends on the size of your battery pack and how much you need to charge. On your P100D if you arrived at 0 at charged to 50% you'd spend roughly $6 and spend half an hour. Going from 50% to 90% would be another half an hour and cost another $6. Going from 90-100% would be another half an hour and cost $3. Total from 0-100% would be roughly $15 and take an hour and a half.
That's all rough estimates based on the tapering curve as your battery gets full assuming the temperatures are all good and you aren't sharing a charger.