Saturday, March 14, 2020

Suburban 5-4-and-a-Door Solar: The Cost to Charge an EV

Thanks to the highways gods accepting our sacrifice of the family minivan on I-75 over the Christmas holiday, we now own an electric vehicle. With our solar array in place, we moved to a "PEV" plan from Georgia Power a while back. Under the PEV plan, the cost of electricity overnight (when the solar panel is not generating) is a fraction of what it costs during the day (when our solar array is offsetting the energy that we use). The plan makes sense even without an electric vehicle.

Since our solar array gives us access to all of the data on how much electricity we use, generate, import, and export, we can figure out exactly how much it costs to charge our new car. We charge overnight, when the cost of electricity is the lowest.

In the graph below, a normal overnight is compared to an overnight when the car is being charged. These were two consecutive nights, so all other variables (weather, etc.) were equal. In this case, the car range started around 50 miles and was charged to 90%, which is just over 280 miles.

The power used overnight on a normal day was 14.7kWh. The power used overnight on a charging day was 45.1kWh. The current charge per kWh from 11pm to 7am is 1.39 cents/kWh.

The cost to charge our EV on the PEV plan is $0.43 (43 cents). That's less than 0.2 cents per mile.

For comparison, current gas prices near me are $2.15 per gallon and our other car gets 30 miles/gal on a very good day. That's 7.2 cents per mile (almost 40 times more expensive).

No lofty conclusions here, just some interesting numbers.

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