Expected vs. real charging rates on 120 V and 240 V chargers

Recently my wife and I bought a 2015 Plug-In Prius. We live in an apartment and don't have a place to charge it nightly, so we thought we would charge it at least once a week in hope that this would maintain the EV battery until we get a home (about 2-3 months out).

Today we plugged it in to a 240 V ChargePoint charging station that is rated for 6.6 kW maximum power output. Due to the amperage limitations (12V for both 120 and 240 VAC connections), we were expecting a charge rate around 2.8 kW and a total charging time of about 1.5 hours. However, the car charged at 2.3 kW for about five minutes, then fell back to 1.3 kW for the remainder of the hour for an average rate of 1.34 kW. Is this typical?

Additionally, looking at charging stations in my area, some charge per kW whereas others charge per hour. Of those that charge per hour, the prices vary wildly between locations. Has anyone had any luck convincing providers to change their pricing models?