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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 (EV).  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 2021 for under $10,000.

From a Leaf owner:  “In two years we have averaged driving about 8,000 miles per year on our all electric Nissan Leaf.  Newer models have a range of 150 to 200 miles.  Charging the car battery uses about 2,000 kilowatt hours annually. That’s 4 cents/mile at 15 cents per kWh for electricity compared to $0.10 per mile at 30 mpg when gasoline costs $3.00 per gallon. Our $0.06 per mile savings for not buying gasoline is about $500 annually.  If the cost of a 1.6 kilowatt solar array (to generate 2,000 kWh annually) is $3,000 after the federal tax credit, our solar investment will be recovered in about six 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, suspension 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 $340 (assuming $0.10 per mile with 30 mpg and $3.00 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 12 percent ($340 savings annually vs. $2,000 cost) and the initial cost will be recovered in about six years depending on future cost of gasoline.

A similar analysis for someone without grid-tied solar net metering is a comparison between grid power and gasoline.  The cost of 1,200 kWh from the grid could be $180 (15 cents per kWh) to drive 3,400 miles. The ROI for purchase of the Volt is calculated as $120 savings for each 3,400 miles ($300 avoided cost of gasoline at $3.00 per gallon, minus $180 cost of electricity to charge the car battery).

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 1,200 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.  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 usage above 300, 1000 and 2000 kWh.

To maximize battery life, Nissan recommends that Leaf owners limit charging the car’s battery to 80 percent.

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.  The general rule of thumb is to plug in and charge whenever you can.

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.

Newer Nissan EVs are capable of bi-directional energy transfer.  Leafs sold in Japan can provide power to a home.  Someday they will be available in other countries.  Offices of the Nissan factory in Tennessee are powered by batteries in a fleet of corporate vehicles that are charged at night with low cost power from TVA.
Comments from an EV owner  “Our 2015 Nissan Leaf purchased in 2018 at reasonable cost and with low miles has become the preferred local vehicle. It’s a joy to drive and has no oil changes, no muffler, catalytic converter or emissions.  Maintenance is tires, brakes, suspension, windshield wipers and light bulbs.  Heated seats and steering wheel are a pleasure in winter months.

We average about 20 miles daily (7,000 miles annually) and charging is mostly with a 110V wall outlet.  Free public chargers installed by the city at Switchyard Park have been appreciated.  Energy usage from our Duke solar net metering is roughly 1,000 kWh for 4,000 miles.  After adding a few more solar panels. our home and EV (electric vehicle) have been net zero from the grid for several years.

The original Leaf 24 kwh battery capacity is similar to a solar backup battery system.  Newer Leaf battery sizes have increased to 30, 40 and 60 kWh with about 60 percent of the stored energy usable for driving.  Battery life is extended by not fully charging or discharging.  When the charge level is below 20 percent, warning lights are activated and the GPS screen shows locations of nearby public chargers.  We normally charge to 70 or 80 percent of capacity.  Batteries are sensitive to heat and cold; batteries get hot when charging.

Our 2016 Toyota Prius hybrid ICE (internal combustion engine) is used for travel, consistently providing mid 50s miles per gallon on the highway.”

Category: Financial Issues

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