# PV + EV = The Future

PV + EV = The Future.

You own one already (lucky dog) or you are dreaming about purchasing a fully electric car, and are obsessing about what it would take to charge that car with solar energy produced with your own rooftop solar panels. Well, there is simple math to gain a good idea of how many solar panels this green energy nirvana would require. To get started down this road, there are a few things to know.

First, to make a calculation realistic, you will want to estimate the annual number of miles you plan to drive your EV car. In the U.S., the average driver logs 12,334 miles each year so we’ll still with 12,000 as an example to keep it simple.

Second, you’ll need to determine the annual estimated kilowatt-hours (kWh) to power your snazzy new electric car. An average electric vehicle will drive approximately 3 miles per one kWh of electricity. To make this calculation, simply divide your estimated annual mileage by three. If you drive 12,000 miles a year, you’ll need approximately 4,000 kWhs of electricity to power your new ride.

Estimate Annual Mileage / 3 = Annual kWh’s to Power EV

Finally, now that you know your estimated mileage it’s time to determine your solar PV system size. A typical Minnesota solar PV system will produce approximately 1,200 kWh’s of electricity per 1kWdc of system size (*). For example a 5kWdc solar PV system will produce approximately 6,000 kWhs of electricity. To calculate the system size of a PV array to offset 100% of your estimated annual mileage, simply take the “Annual kWh’s to Power EV” divided by 1,200.

Annual kWh’s to Power EV / 1,200 = kWdc System Size to Offset Annual Mileage

Note, these solar array systems installed on your rooftop to charge your EV car would likely be tied into your overall electric grid. Of course, the more miles you drive, the more solar panels you’ll need. However, if you do drive further than your estimated annual mileage, you would either obtain the extra electricity either from the grid or from a nearby charging station. To make charging on the road easy on the move, there are aps for your phone such as Charge Point and PlugShare that you can have your credit card information saved so charging is simple and fast. These apps also populate google maps with charging station locations near you.

Your utility may also have special EV rates allowing you to benefit from less expensive charging power at night, while your solar array makes up the difference during the day. Utilities such as Xcel’s EV Charging Program and Dakota Electric’s EV charging incentives, assist electric vehicle owners in reducing their energy charging costs. Please contact us to inquire further on special utility EV rates. The math works. PV + EV will drive the future.

* Solar PV systems are measured in “DC” (direct current) but also have an “AC” (alternating current) rating for the inverters utilized. The “DC” system size is simple the sum of all solar modules in direct current ratings and the “AC” system size is simply the sum of the inverters in “AC” ratings. For the purpose of this exercise, we focused on the “DC” rating of the solar PV system.

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