Electric cars and solar energy: the nirvana of sustainability?

Witnessing the acceleration of an electric car is truly amazing: it’s akin to watching a movie in fast forward without any sound. Just a sleek, peppy vehicle gaining speed at an unusually rapid rate. The advent of hybrid and all-electric vehicles is not only an important milestone in personal transportation, but it also has the potential to transform the global energy market. After all, according to the US Energy Information Administration, transportation consumes almost 30 percent of the US energy supply. What goes in the vehicles is only one part of the the equation. What comes out is also very significant: US Department of Transportation estimates that about 30 percent of all green house gas emissions in the US can be linked to burning fossil fuels for various transportation needs.

However, even if we were to replace every single conventional automobile in North America with electric vehicles, the problem wouldn’t be resolved entirely. We would simply increase the demand for electricity, which is overwhelmingly generated by burning, you guessed it, fossil fuels as well (almost 70% of electricity in the US comes from coal and natural gas). Therefore, when it comes to the environmental footprint of electric vehicles, the source of electricity is of paramount importance. No matter how efficient the electric vehicle itself may be, if the electricity is generated using coal or another type of fossil fuel, then the environmental benefits of the vehicle itself will be limited. However, if the source of electricity is also environmentally friendly, then electric vehicles can emerge as the cornerstone of a low-carbon economy. This is where solar energy has an edge. Barring the greenhouse gas emissions during the manufacturing and transportation of the solar panels, solar energy is virtually emission free.

However, most consumers don’t base their ultimate purchasing decisions on environmental criteria only: the cold hard reality of economics kicks in sooner or later. Given the choice, many electric vehicle owners would opt for the cheapest source of electricity, since it’s a commodity with very few distinguishing features for the end user. Thus, solar energy has to stand on its own two feet to win the hearts and minds of the consumers. If the cost of solar electricity to charge an electric vehicle is comparable to the cost of competing electricity sources, then the environmental edge of solar will probably tilt the preference of the consumers towards solar energy.

Let’s estimate the amount and cost of solar electricity

Crunching some numbers using Sunmetrix Discover can give a better idea about the potential for charging your electric car using solar panels. Using California as a test ground, let’s take a look at the case of an electric car owner living in Los Angeles. The Solar Score of Los Angeles is 81, and an averaged-sized residential solar panel kit of 5kW installed capacity would produce about 10,000 kWh of electricity throughout the year. The cost of this electricity is very much dependent on the cost of the initial installation. Solar Energy Industries Association estimates that the average cost of a residential installation was $5 per installed watt capacity in 2013 in the US. Thus, a 5 kW system would cost around $17,500 ($25,000 minus the 30% federal tax credit). This gives us sufficient information to estimate the cost per kWh generated (also called the levelized cost). Assuming a 20-year system lifetime, adding a 20% margin for future contingencies (such as an inverter replacement), the cost per kWh of solar electricity at this location is about $0.105 per kWh. We should highlight one of the distinct advantages of solar power here: this rate is “locked-in” and it will not increase over time. Compared to the average utility price of $0.16 per kWh in California (as reported by the US Energy Information Administration), solar energy at this location is already cost competitive.

Now let’s run the numbers for Tesla Model S

Tesla Model S (image credit: Tesla Motors)
Tesla Model S (image credit: Tesla Motors)

The electric car for this case is a Tesla Model S with a battery pack of 85 kWh and a range of 300 miles. In order to completely charge this battery pack, we will need about 100 kWh of electricity. This amount is higher than the battery capacity itself, since the charging process is not 100% efficient and there are energy losses due to the internal resistance of the battery and other factors. Based on the 300 miles to 100 kWh ratio and assuming a driving range of 50 miles for every single day of the year, our Tesla S would need about 6000 kWh of electricity during the year, or about 60% of our total solar electricity. What about the cost for mile? At 50 miles a day, the annual range is 18,250 miles. The total cost of solar electricity for 6000 kWh is $630 based on the $0.105/kWh rate. Thus, for $1 we can drive, on average, about 29 miles! Considering that a conventional automobile with 25 miles per gallon fuel consumption would cost about $2600 to fuel up for the same annual range,  the solar-electric vehicle combination seems very attractive.

Our verdict: Mix of sun and cloud today, but very sunny for tomorrow!

The analysis above doesn’t mean that owning electric vehicles are cheaper than conventional models today. The initial cost of electric vehicles are still considerably higher than that of their fossil-fuel cousins. However, as production rates increase and more technological advancements are made, electric vehicles can become an excellent choice. Combining these vehicles with solar energy not only creates a huge environmental benefit, but it also translates into cheaper operating costs. Please bear in mind that almost all of the solar numbers above are location specific. Los Angeles is blessed with very high levels of solar radiation, which of course decreases the levelized cost of solar electricity considerably. In order to see how your location compares and see if there are any potential savings, why not take a test drive on Sunmetrix Discover?

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