Do electric cars improve energy independence?

Many Americans consider energy independence a top concern for environmental, economic, and security reasons. One of the main benefits of electric cars is that they can be powered by any resource that generates electricity. When you purchase an electric car, your fuel doesn’t come from a gas pump – it comes from the electric grid.

In the United States, most electricity is generated by coal, natural gas, or nuclear power. However, a growing percentage of U.S. electricity comes from renewable resources: in 2018, 17 percent came from hydropower, wind, biomass, solar or geothermal energy sources. In fact, more than a million U.S. homeowners have chosen to take home energy generation into their own hands by installing emissions-free home solar panel systems.

Solar panels and electric cars are a match made in heaven ­– when you install a solar energy system on your home, you can use it to power your home and charge your electric car for emissions-free transportation. The cost of solar is falling rapidly, and companies from Tesla to Nissan are manufacturing electric cars for your daily use.

Now, the ability to install a solar PV system large enough to power both your home and your car is an option within reach. Whether you choose to buy an electric car and install a solar panel system with an EV charging station all at once or stagger your purchases, pairing electric cars and solar panels is one of the best ways to increase your energy independence.

If you want to invest in truly energy-independent transportation, you’ll need to pair your electric car with solar panels. There are two things that you need to know to determine how to optimize your solar panels and electric vehicle:

• Miles-per-gallon equivalent (MPGe) of the electric car you’re interested in

• How you plan to use your car, i.e., the average distance you will travel

With these two pieces of information, you can estimate of how much extra electricity charging your electric car will require. Then, when you install your solar panel system, you can work with your solar installer to size your system based on your driving needs and your monthly home electricity use.

Electric car MPGe

Since electric cars don’t run on gasoline, the EPA rates them based on how many kilowatt-hours (kWh) it takes for the car to drive 100 miles, which they convert to a “miles-per-gallon equivalent” (MPGe). Electric cars are much more efficient (in terms of converting energy into movement) than gasoline-powered cars. EVs convert about 59 to 62 percent of the electrical energy from the grid to power at the wheels. By comparison, conventional gasoline vehicles can only convert 17 to 21 percent of the energy stored in gasoline to power at the wheels.

Most new electric cars on the market get anywhere from 70 to 135 MPGe. You can use the U.S. Department of Energy’s Fuel Economy website to find and compare the kWh/100 miles and MPGe ratings for all of the electric vehicles on the market in the United States.

How do you plan to use your EV

Once you know EPA’s fuel economy rating for your chosen vehicle, you can estimate how much extra solar electricity you’ll need to charge your car. This will depend on how you plan to use your EV: will you use it for short errands a few times a week or for a daily commute? Make an estimate about your weekly number of miles traveled to calculate the “extra” amount of electricity you’ll need your solar energy system to produce for driving.

Here’s an example: the 2017 Nissan Leaf, an all-electric vehicle, requires 30 kWh of electricity to drive 100 miles. If you drive 25 miles per day, that means you’re using approximately 7.5 kWh of electricity per day (100 miles ÷ 25 miles per day = 4, then 30 kWh ÷ 4 = 7.5 kWh). This results in just over 2,700 kWh of new solar electricity needed in a given year (7.5 kWh x 365 days = 2737.50 kWh per year).

Armed with this information, you can work with your solar installer to design a solar panel system that will generate sufficient power to cover both your home and your electric car. If you’re not ready to make the investment in both an EV and solar energy system at the same time, you’ll need to install a solar PV system that can be added onto later as your electricity needs increase.

First things first: don’t delay going solar just because you might want to get a bigger system in the future. If you wait to install solar, you could miss out on the state and local financial incentives that are available today – plus, you’ll have to continue paying for electricity from your utility every month.

By sizing your solar energy system for future usage and ensuring your system is “add-on friendly”, it’s easy to find an option that generates enough electricity to power your home today and can charge your electric car in the future. Here are a few ways you can ensure your system will be ready to take you to full energy independence:

• Design your system so that it’s easy to add panels later on. Solar panels require what is known as an inverter to turn solar energy into useful electricity for your home. The size of the inverter depends on how the size of your system. If you know how many more panels you’ll need to add to your system later on, you can install an inverter that can handle the capacity of your existing panels plus the new ones you plan on adding after purchasing your electric vehicle. Another option is to install smaller inverters that are located at every solar panel, known as microinverters, rather than one large centralized inverter.

• Install a second, smaller solar energy system. So long as you have enough space on your roof, you can add a second system to your home whenever you need it. Note, however, that homeowners can’t claim the federal tax credit for solar more than once on the same property.

• Calculate your future use, and build a bigger system to match. If you know that your electricity use will increase in the next year or two and have access to financing, you can build your solar energy system based on your future electricity use. This isn’t always an option – some utilities won’t approve systems that go significantly beyond your historical electricity use, so be sure to talk to your solar installer about your options first.

Another option is to “make room” later down the line by implementing energy efficiency upgrades to your home, which has the added benefit of reducing your overall energy costs. Consider switching out lightbulbs, installing a programmable thermostat, or upgrading your appliances to free up some of the electricity your solar panels generate for future use in an electric vehicle.

It’s worth noting that the strategies above work not just for electric cars, but also for any other additions or changes you make to your house that will increase your electricity usage. If you’re considering adding an electric heat pump system, electric water heater, or an addition on your home, you can expand your solar energy system to take your future electricity use into account. In any situation, installing solar panels to power your home (and your transportation) is one of the strongest moves towards complete energy independence that you can make.

EnergySage partners with Qmerit, a home EV charging installation leader who works with a trusted network of certified installers. They can help you quickly and easily install your home EV charger.

Find local EV charger installers and get a quote.