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What does it cost to charge an electric plug-in vehicle with solar energy?

The payback for using solar to charge an electrical vehicle is better than payback for using solar energy in the home.

The pre-owned Toyota Prius plug-in or Chevrolet Volt with less than 40,000 miles can be purchased in 2017 for under $20,000.  Prices are lower for higher mileage vehicles. Take a look at this price and performance comparison of 2013 models of a Prius plug-in vs. the Volt.

From a Leaf owner:  “In 16 months we have averaged about 950 miles per month on our all electric 2013 Nissan Leaf with a range of about 70 miles in winter and up to 90 miles in warm weather.  From my location in Nashville Indiana it is very usable for trips to Columbus or Bloomington. Charging the car battery uses about 300 kilowatt hours a month, or 3 miles per kwh. That’s 4 cents/mile at 12 cents per kWh for electricity. The Leaf cost of 4 cents/mile compared to gasoline would translate to 55 mpg when gas costs $2.20 per gallon or 70 mpg if gas costs $2.80 per gallon.

“The added bonus to our Leaf is that there are literally no other expenses: no oil changes, spark plugs, air filter, belts, muffler, no noise and no exhaust pollution. The car has been in production since 2010 with 95 % of the cars still on the road. The batteries are made in Tennessee. I have been told that the battery performance of the Leaf is excellent. Every time I have gotten into the car and pushed the ON button, it starts and away we go, leaving no trail at all in the air behind me. Solar panels provide about 85 % of our house electricity. Now we need a few more panels for my electric car. ”

The Chevrolet Volt uses about 1,200 kWh to drive 3,400 miles (85 trips of up to 40 miles in all electric mode).  The avoided cost of gasoline is $340 (assuming 10 cents per mile with 30 mpg and $3 per gallon gas cost).  If the cost of a one kilowatt solar array (to generate 1,200 kWh annually) is $2,000 after the federal tax credit, then the ROI for solar energy will be 17 percent ($340 savings vs. $2,000 cost).  When gas costs $2.10 per gallon at 7 cents per mile with 30 mpg, the ROI is 12 percent.

A similar analysis for someone without grid-tied solar net metering is less favorable where the comparison is between grid power and gasoline.  The cost of 1,200 kWh from the grid could be $140, or 12 cents per kWh, to drive 3,400 miles. Now the ROI for purchase of the Volt is calculated as $200 savings for each 3,400 miles ($340 avoided cost of gas at $3 per gallon, minus $140 cost of electricity).  If you drive 10,200 miles in a year, your savings would be $600.

However, the accuracy of any analysis depends on its assumptions.  Your actual cost of grid power may be between 8 cents and 20 cents per kWh.  The incremental cost of electricity depends on your rate, which utility company and how many kWh you are using.

The first 300 kWh per month with Duke Energy is more expensive, with increasing discounts for above 300, 1000 and 2000 kWh. The SCI REMC (Martinsville) has seasonal and time of day rates with lower cost at night and spring and fall months.


Category: Financial Issues

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