There is no doubt that electric cars are more eco-friendly than fuel guzzling cars — but are they really eco-friendly? This has been a daunting question for many who have switched to these cars from their fuel cell vehicles. Tesla CEO Elon Musk finally answered the question when David Kennedy, an employee at Tesla tweeted the company’s supercharger network, which it uses to charge its cars, derives its power mostly from coal-powered plants.

Responding to him, Musk stated, “ All Superchargers are being converted to solar/battery power. Over time, almost all will disconnect from the electricity grid.”

Read: Tesla Superchargers In 2017: Faster Charging, Expanded Network, China Presence And More

The quagmire of electric cars, from the start, has been the source of electricity. If the electricity is derived from non-renewable sources, which actually pollute the environment, they might not be eco-friendly. It could actually make them lesser polluters than fuel guzzlers, not eco-friendly in essence. Using Musk’s technology, including the company’s Powerpacks energy storage at Tesla’s Supercharging stations, these supercharger stations could actually be solar-powered, especially since the company is actually now one which produces solar panels, since its acquisition of solar energy company SolarCity last year.

Tesla is also set to come out with the version three of the superchargers, which will have 350 kilowatts power output and off grid solar energy and power packs. The new superchargers are also expected to lower the charging time from an hour to ten minutes.

Tesla has been expanding its Supercharging network recently and the company has an ambitious goal of reaching 10,000 superchargers by the end of 2017. The company will also start delivering its first mass-market car, the Tesla Model 3 next month. The company stated in April some of its Superchargers would be solar powered, but now CEO Elon Musk has stated that all of these superchargers will be powered by eco-friendly sources of energy.  It is unclear though, that whether Tesla would be powering all of its under-construction superchargers and to be constructed Superchargers with solar energy.

According to Electrek, only 6 of 800 or so current Superchargers are solar powered.

Read: Tesla Supercharger Network: More Chargers In More Locations For 2017

Whatever be the case, Tesla will need more Supercharger stations if it wants to find more takers for its electric cars. If the technology has to go mainstream, it will have to compete with the convenience that gas-guzzling vehicles offer — just like you can fill up your tank, by going to nearby gas station, in a very short duration, the alternative should be that you should easily be able to charge your car and take a long drive without worrying about the battery running out. If the company succeeds in actually building such a large number of Superchargers, it would actually succeed in its goal of mainstreaming the technology. — an endeavor in which the upcoming Model 3 might help.