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

Solar owners are more likely to drive hybrid or electric vehicles. The savings for using solar to charge an electrical vehicle is better than for using solar energy in the home.

The pre-owned Chevrolet Volt or Nissan Leaf can be purchased in 2019 for under $10,000. 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 two years we have averaged driving about 800 miles per month on our all electric Nissan Leaf.  Newer models have a range of 150 to 200 miles.  Charging the car battery uses about 200 kilowatt hours a month. That’s 3 cents/mile at 12 cents per kWh for electricity compared to $0.08 per mile for gasoline at 30 mpg when gas costs $2.40 per gallon. Our $0.05 per mile savings for not buying gasoline is about $500 annually.  If the cost of a two kilowatt solar array (to generate 2400 kWh annually) is $4,000 after the federal tax credit, our solar investment will be recovered in eight years (or sooner if gasoline prices increase).”

An added bonus to the all electric Leaf is that there are no other expenses: no oil changes, spark plugs, air filter, belts, tailpipe or muffler, no noise and no exhaust pollution.  Maintenance is mostly limited to tires, brakes, shock absorbers and windshield wipers. The car and its batteries are made in Tennessee.

The Chevrolet Volt uses about 1,200 kWh to drive 3,400 miles (85 trips of up to 40 miles in all electric mode before switching to its gas engine).  The avoided cost of gasoline is $270 (assuming $0.08 per mile with 30 mpg and $2.40 per gallon gas cost).  If the cost of a one kilowatt solar array (to generate 1200 kWh annually) is $2,000 after the federal tax credit, then the ROI for solar energy will be 14 percent ($270 savings vs. $2,000 cost).

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 (12 cents per kWh) to drive 3,400 miles. The ROI for purchase of the Volt is calculated as $130 savings for each 3,400 miles ($270 avoided cost of gas at $2.40 per gallon, minus $140 cost of electricity).  

The cost of grid power is usually between 10 and 20 cents per kWh. The value of electricity produced by a one kilowatt solar array (generating 1200 kWh annually) is $120 at 10 cents per kWh or $180 at 15 cents per kWh.

However, the accuracy of any analysis depends on its assumptions.  Your actual cost of grid power may be between 10 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 additional discounts for above 300, 1000 and 2000 kWh.  

To maximize battery life, Nissan recommends that Leaf owners charge the car’s battery to 80 percent and no more. You also should avoid leaving your vehicle for extended periods of time with zero or very little charge, since this can wear down the battery.

The general rule of thumb is to plug in and charge whenever you can.  Under 30% charge is generally considered low and thus you should not let your EV sit at that low state of charge for an extended period.

Effective battery range of an EV rated for 200 miles at full charge would be about 100 miles (from 80% to 30%)

The typical average for local driving (8,000 miles annually) would be under 25 miles per day.


Category: Financial Issues

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