The world has been keeping a close eye on Elon Musk and his innovative "cleantech" ventures. Now that Tesla and SolarCity have combined forces, even design-conscious homeowners can pair electric cars and solar panels to wage a war against grid reliance and energy dependence. Here's how pairing your Tesla with solar panels can help shrink your carbon footprint.
Electric vehicles like those manufactured by Tesla can actually serve as a form of battery storage for solar energy. The process is simple:
1. Install solar on your roof to generate electricity by harnessing the power of the sun
2. Take that photovoltaic energy and use it to charge your Tesla Model S or Model 3 when your solar panels are producing more electricity than you need to power your home
That one-two punch is exactly what Elon Musk had in mind when his company moved to acquire SolarCity. Of course, this was this all possible before the Tesla-SolarCity merger – a Chevy Volt or Nissan Leaf owner didn’t need Elon Musk’s “master plan” to realize that electric cars can be paired with solar energy. However, Musk’s latest move targets the layman homeowner, extending beyond the early adopters of clean energy who paired their Leaf or Volt with home solar panels years ago.
By bringing two of the world’s leading solutions to emissions reduction under one roof, Tesla can cut operating costs in development and installation, helping homeowners to understand clean energy financing options as a combined cost rather than trying to conceptualize the headache of multiple individual energy investments. In a sense, Tesla is making clean energy simple because it needs to be simple.
Now that millions of homeowners are considering the prospect of a zero emissions home, a number of questions are arising in the renewable space. How do you connect solar panels to an electric vehicle? How long will it take for solar panels to charge a car? How many panels will you need to charge your car in the first place?
In order to understand how solar panels and Tesla vehicles complement each other, we first need to understand how electric cars are charged rather than fueled. And because solar panel systems are sized based on the expected energy usage of a household, a homeowner would need to take into account projected energy needs from his or her Tesla in order to get a solar panel system that can generate enough electricity enough to meet that combined demand.
The metric to use here is the kilowatt-hour (kWh), which represents the one unit of electricity consumed. In order to compare electric vehicles (EVs) to automobiles, the EPA uses the amount of kilowatt-hours required for an EV to travel 100 miles as a "miles per gallon equivalent" (MPGe).
According to FuelEconomy.gov, the 2016 Tesla Model S requires 34 kWh per every 100 miles, giving it a fuel economy rating of 98 MPGe. If the ultimate question is how many kWh you need to power your Tesla, it depends on the distance you plan to travel. A short trip 25 miles each way would require roughly 17 kWh of energy, while the energy needed to run errands around town might only require 2 or 3 kWh.
How many solar panels does it take to charge a Tesla?
Once you establish how many kWh you need to charge your Tesla, the next step is to calculate how many solar panels are required to provide that charge. Solar panel electricity production is dependent on a few different factors – to keep it simple, we’ll use an example homeowner who already has solar and is adding additional panels to supply energy for a 2016 Tesla Model S. Let’s call her Barb.
Barb has a 5 kW (5,000 watt) solar system, the average system size for the U.S. residential solar market. She lives in Cleveland, Ohio where solar is not unusually cheap or particularly expensive. In Cleveland, the average annual energy production for 5kW solar systems is 6,071 kWh.
Assuming Barb’s system uses standard 250-watt panels, we then also know that Barb’s current solar array has 20 solar panels (250 W x 20 panels = 5,000 Watts). This means that each of Barb’s panels produces just over 303 kWh of energy in a year (6,071 kWh ÷ 20 panels). Let’s think of this number as Barb’s annual energy production for a single panel.
As we learned above, Barb’s new Tesla Model S has a 34kWh/100 MPGe rating. If we assume she will be driving 25 miles a day, we know that her Tesla is going to be using 8.5 kWh a day (3,103 kWh per year). Assuming each panel produces approximately 303 kWh per year, Barb will need to add roughly 10 more solar panels to her system in order to supply fuel for her new Tesla.
The next question might be “how much does it cost to charge a Tesla with solar?”, or in other words, how much extra will Barb need to pay for those 10 panels. If we assume an average price to install a 250W panel is $185, charging Barb’s brand-new Model S will likely tack on another $2,000 to her solar panel system costs.
Compare that to total money spent at the gas pump every year and we start to see why pairing a Tesla with solar panels makes sense. In the long run, Barb will see concrete energy savings on multiple fronts, and will likely break even on her solar panel investment in seven to 10 years.
If you're planning to go all in on clean energy, hopefully this breakdown helped you to envision the integration of solar and EVs. The next step towards zero emissions is to begin searching for the right EV and start comparing quotes for a solar panel system. The EnergySage Solar Marketplace allows you to compare real pricing data from homeowners in your area and review various financing options for free. For those looking for a personalized instant estimate for solar, try our Solar Calculator.
Vikram Aggarwal is the founder and chief executive of EnergySage, the online solar marketplace. EnergySage simplifies the process of researching and shopping for solar. By offering shoppers more choices and unprecedented levels of transparency, EnergySage allows consumers to select the solar installation quote that provides the best value for them, quickly and easily. Read all of Vikram's posts here.
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