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The battery is rated at 18.1 kWh, with about 14 kWh usable in EV mode. Charging from 0 EV to full takes about 14.6 kWh as measured at the EVSE. As the battery ages, the energy required to charge does get lower, typically to the mid-13 kWh range has been observed.

 

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So does that mean in my case - $0.13 x 14.6 = $1.90

Just make sure that $0.13 is the full charge for power. Some electric companies have a number of line items that are each multiplied by the kWh usage. The actual cost for multiple line items is the total of each item per kWh. Some also have fixed charges per month. You can ignore the fixed charges as you would pay those even if you were not charging you R4P.

 

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I consistently see 15.1 kw when charging from 0 miles on the Kill-O-Watt meter that I use to monitor my charging electricity usage from my 120V outlet. I use the Departure Time charging feature so my R4P doesn't stay connected to the K-O-W meter for too long after it reaches a full charge. Maybe I just have a less efficient setup at home or my K-O-W meter is not measuring as accurately as it should.

That is probably about right for 120 volt charging. Charging losses are related to the amps being supplied. Charging losses at 120 volts will be more than at 240 volts. In addition, there are some minor overhead items that are powered during the active charging time. These are the DC-DC converter fan and the 12 volt battery charger. Since at 120 volts charging takes longer, these overhead items add up to a bit more.

 

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Thanks. I have noticed that during charging the volts seems to stay right around 120 volts and the amps are between 11-12. BTW, is there any way to know what the charging losses are at 120 volts compared to 240 volts? I am thinking of having Level 2 EVSE installed this summer with a 240 volt, 50 amp line. I realize that is more than my R4P needs/uses but I figure I would rather have wiring in place that can handle both current and potential future needs.

There is no real way other than measurement. We can assume that 14 kWh is needed to charge the battery fully from 0 EV miles. i have seen energy use recorded by my 240 volt EVSE at 14.6 - 14.7 kWh, indicating a loss of 0.6-0.7 kWh. This would be the combined loss from overhead (fan and 12 v charger), internal charger loss, battery heat loss, and cable losses from the EVSE measuring point to the car. Your measurement indicated 15.1 kWh at 120 volts, indicating a loss of 1.1 kWh.